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Progress and prospect of hot dry rock exploration and development
WEN Dongguang, ZHANG Eryong, WANG Guiling, ZHANG Linyou, WANG Huang, ZHANG Senqi, YE Chengming, WANG Wenshi, JIN Xianpeng, LIU Donglin, JIA Xiaofeng, LI Shengtao, WU Haidong, LIAN Sheng, FENG Qingda
 doi: 10.16030/j.cnki.issn.1000-3665.202304011
Abstract(185) HTML(173) PDF (6524KB)(29)
The exploitation and utilization of clean energy is a resource and environmental issue of common concern for global sustainable development. As a vital strategic and sustainable future energy, hot dry rock (HDR) has attracted more and more attention. In this paper some thoughts on the future research direction of HDR resources in China are provided based on worldwide experience summary, hoping to provide a useful reference for the future exploration and engineering development of HDR. Since the concept of HDR was put forward in the 1970s, the number of HDR constructed worldwide has been increasingly growing. Although a lot of theoretical and technical breakthroughs have been made, only a small fraction of projects still in operation due to the lack of sustained financial support, induced microearthquakes and other issues. At present, the global development of HDR is gradually entering a new stage of exploration, and the basic theories of HDR to tackle the key problems are strengthening around the world. Since 2012, the China Geological Survey has organized and implemented the nationwide terrestrial HDR resources survey, evaluation, exploration, and development, and significant stage progress has been achieved. A series of fundamental maps have been compiled, such as terrestrial heat flow value, curie surface depth, distribution of acidic rock, and heat-controlling structure in China. The resource potential of terrestrial HDR in China has been preliminarily estimated and provided a sounding basis for the target site selection. HDR exploration and evaluation have been carried out in typical areas of Qinghai, Shandong, Hebei, Shanxi, and Jiangsu provinces, and a breakthrough has been achieved in the Gonghe Basin of Qinghai. The first HDR resources exploration and production demonstration project in China was carried out in 2019, which made a series of meaningful outcomes in deep HDR exploration, high-temperature hard rock drilling, large-scale reservoir stimulation, reservoir connectivity and flow circulation, organic Rankine cycle (ORC) power generation, etc. The large-scale reservoir stimulation was carried out in 2020, and the first power generation test was completed in 2021. In general, the global exploration and development of HDR has made great progress. Practice has proved that HDR resources are a promising green energy and are expected to become an inexhaustible energy support for the world in the future. However, there is still a large gap between the existing path of HDR development and utilization and the economics of its supporting technologies compared with commercial development expectations at present. Although the development of HDR resources in China has achieved a breakthrough from "0" to "1", there is still a long way to go from the international level. In order to solve the problems of large-scale and economic development, there is still need to promote disruptive technological innovation in high temperature hard rock drilling and completion, fine characterization of deep reservoirs, safe large-scale reservoir construction, efficient heat transfer and heat recovery and other aspects.
Single well injection withdraw (SWIW) - based tracer test approach for in-situ permeability estimation in an enhanced geothermal system
XU Hanying, JIANG Zhenjiao, XU Tianfu, CHEN Xuanyi
 doi: 10.16030/j.cnki.issn.1000-3665.202209010
Abstract(3029) HTML(517) PDF (3615KB)(47)
Efficient estimation of near-wellbore permeability is critical for evaluating fracturing effect and updating fracturing plan. However, due to technical or cost constraints, there is still a lack of methods for in-situ testing and estimating near-wellbore permeability in deep geothermal reservoirs. Considering that the hydraulic fracturing is often associated with injection breaking and back drainage to control the reservoir pressure, this study proposes a single-well-injection-withdraw-based tracer test approach and two permeability interpretation methods based on numerical and analytical solutions, which allow in-situ permeability estimation at low cost. Implementation of the proposed method at a realistic enhanced geothermal system indicates that the numerical interpretation method can still reasonably estimate near-wellbore permeability under the condition of incomplete tracer breakthrough curve in the single well injection and withdraw test, but the computational efficiency is low. Once the tracer breakout curve is relatively complete (i.e. the peak tracer concentration is monitored), the analytical method can be used to quickly estimate the permeability. However, the analytical method cannot accurately consider the long-distance tracer migration process inside wellbore and the influence of dispersion on the tracer breakthrough curve, hence the accuracy is relatively low. The numerical and analytical permeability estimations are at the same order of magnitude. The results suggest that in addition to the numerical method, the analytical method can still be used as an effective method for in-situ rapid permeability estimation. The proposed methodology may provide a new tool for in-situ permeability estimation in deep geothermal reservoirs.
Determination of geotechnical parameters based on the unsupervised learning method
RUAN Yongfen, LI Penghui, ZHU Qiang, WANG Yong, YAN Ming
 doi: 10.16030/j.cnki.issn.1000-3665.202207046
Abstract(3755) HTML(129) PDF (4419KB)(45)
With the development of urban engineering construction, the issue of construction engineering accidents has become more and more prominent. The geotechnical parameter interval obtained by using the traditional methods cannot meet the needs of actual engineering. Based on the idea of unsupervised learning, the peaty soil with the worst engineering properties is considered, and 8 physical indexes are selected as the input set. The principal component analysis (PCA) algorithm is used to realize the dimensionality reduction of multi-sample and multi-parameter decoupling, and the correlation and sensitivity of each physical index is obtained. Combined with its correlation and sensitivity, the comprehensive evaluation value of physical indexes of peat soil with different buried depths is given. The k-means clustering is used to analyze the relationship among physical index, and comprehensive evaluation value and engineering characteristics of peaty soil provide a theoretical basis for the selection of geotechnical parameters. The supervised learning method-BP neural network algorithm is used to analyze the unsupervised results and verify the accuracy of the (PCA—k-means) algorithm model. The normal samples obtained by clustering analysis are optimized by a variety of truncation methods to obtain a reliable value range, and the value results are compared with the actual engineering values to verify the rationality of the model engineering parameters. The algorithm model is of good engineering application value. The research results can provide references for engineering investigation, design and construction parameter values, and also provide a new analysis method for geotechnical parameter value analyses.
Abstract(6639) HTML(2117) PDF (2927KB)(916)
A study of the law of groundwater seepage movement in a confined aquifer under seismic waves
LIANG Wenyu, LAN Shuangshuang, GU Hongbiao, QIAO Peng, MAO Zhengtan
 doi: 10.16030/j.cnki.issn.1000-3665.202212020
Abstract(0) HTML(0) PDF (6685KB)(0)
The classical groundwater seepage theory was established on the basis of the principle of water equilibrium, which cannot explain the phenomenon of well water level change caused by natural seismic activities and other external loads, and is not conducive to the in-depth understanding of the role of groundwater seepage movement in various environmental geological disasters. To solve this problem, a mathematical model of pore pressure change of a confined aquifer driven by seismic wave stress is constructed based on the fluid-structure coupling dynamic theory. The numerical verification of the model is realized by using the software Comsol. The change characteristics of well water level are inversely performed by using the Cooper theory, and the results are compared with the change characteristics of well water level caused by strong earthquakes in the Sichian-Yunnan region. The influencing factors of seepage movement of a confined aquifer under earthquake are studied by changing the simulation parameters. The results show that when seismic wave loads act on the confined aquifers, pore pressure oscillates in the same period as the seismic waves, and the amplitude, frequency and hydraulic slope of the seismic waves have significant effects on the pore pressure, while the coefficient of permeability and porosity have little effect on the change characteristics. At the initial stage of seismic wave loading, pore pressure increases rapidly, and then part of the water in the aquifer is slowly discharged. The load pressure gradually transfers to the granular framework, and the rate of change of pore pressure slows down and tends to reach a new equilibrium. The variation characteristics of well water level are closely related to pore pressure, and the oscillation period and variation pattern are consistent with pore pressure, but the amplitude is different. Generally, the oscillation rises and tends to be stable, which is basically the same with the variation pattern of well water level observed in the Sichuan-Yunnan region. The results are of valuable exploration significance for the establishment and improvement of groundwater seepage theory under stress, and can enrich and expand the research ideas and application fields of traditional groundwater dynamics and classical fluid-structure coupling theory.
Water transport process and simulation of layered soils with different configurations in an arid region
WANG Qiangmin, ZHAO Ming, PENG Hongjie, HU Guiming, MA Kaifeng, GUO Keke, LIU Pu
 doi: 10.16030/j.cnki.issn.1000-3665.202211076
Abstract(0) HTML(0) PDF (4128KB)(0)
The mining area in north China is located in the arid and semi-arid zone, in which the surface water resource is sparse and the ecological environment is fragile. Coupled with the exploitation of mineral resources, the land has been degraded seriously. How to realize the efficient reclamation of soil and the effective utilization of soil water is an urgent scientific and technical problem. In this study, the layered soil with different configurations is set up for water transport and infiltration test to monitor the moisture changes in the soil profile. Hydrus-1D is used to simulate the rainfall infiltration process and reveal the water transport characteristics of layered soil from three aspects: soil moisture, water potential and water flux. The scenario simulation is conducted based on the optimized model to explore the effect of interlayer characteristics on shallow soil water. The results show that the interlayer significantly changes the distribution and transport of soil water, and the soil water potential is continuously distributed at the interlayer interface, while the soil water abruptly changes at the interlayer interface. Although loess interlayer and weathered sandstone interlayer both block the infiltration of soil water, the principle and the source of water increase are different. The former is the retention of soil water above the interlayer due tothe poor permeability of loess, while the latter is the retention of water above the interlayer due to the small matrix potential of the coarser interlayer. According to the results of the model, it is suggested that setting loess interlayer of 20 cm thick at the depth of 40 cm of aeolian sand is conducive to increase soil moisture above the interlayer for vegetation utilization. Summarily, the results can provide a theoretical basis for understanding and mastering the layered soil hydrological process in arid regions and optimizing the soil reconstruction mode in the process of land reclamation and ecological restoration.
Identification of groundwater pollution intensity and hydraulic conductivity field
WU Yanhao, JIANG Simin, WU Zijun
 doi: 10.16030/j.cnki.issn.1000-3665.202208042
Abstract(0) HTML(0) PDF (7448KB)(0)
The pollution source parameters and hydraulic conductivity field are the most important parameters of groundwater numerical models when making groundwater pollution remediation plans. However, previous studies focused mainly on the identification of single type parameters. The groundwater pollutant transport model (MT3DMS) and data assimilation method (iterative local updating ensemble smoother, ILUES) are used to form a solution framework for groundwater pollution source identification, and Karhunen-Loève expansion technique is used to realize parameter dimension reduction of the hydraulic conductivity field. The joint inversion of groundwater pollution source intensity and hydraulic conductivity field are also realized by assimilating hydraulic heads and concentration data. The results show that (1) the ILUES algorithm can accurately identify pollution source parameters and permeability coefficient field, and it is of high universality. (2) Accurate characterization of spatial heterogeneity of the coefficient of permeability is the key to predict pollutant migration path and inversion of pollution intensity. (3) The ILUES algorithm parameters affect the inversion results. By considering the computational efficiency and accuracy, the optimal sample set size (Ne=4000) and the optimal parameter combination of ILUES algorithm (α=0.4, b=4) can be obtained. However, in practical engineering cases, the empirical combination (α=0.1, b=1) is more recommendable if the requirement for accuracy is not too high. The results of this study have strong practical significance for regional groundwater resources investigation, evaluation and management, and can provide technical support for later groundwater pollution prediction and optimization of groundwater monitoring well networks.
Research on the prediction method of water gushing volume under the blasting vibration effect of a sub-sea Tunnel
LI Jiacheng, WANG Weiming, LYU Xianzhou, WANG Xiaojie, PAN Zhixin
 doi: 10.16030/j.cnki.issn.1000-3665.202205055
Abstract(2) HTML(1) PDF (0KB)(0)
Prediction of water inflow of a sub-sea tunnel under the blasting vibration effect is still a difficult subject. This paper takes the sub-sea tunnel between the Wawuzhuang Station and Guizhou Road Station of the Qingdao Metro Line 1 as the engineering background. Based on the equivalent continuum model, the mirror image method is used to deduce the calculation formula for the water inflow of the sub-sea tunnel considering the damage area factor. Through forward modeling and inversion, combined with numerical simulation results and actual engineering monitoring results, the correctness of the formula is comprehensively verified, and the influence mechanism of damage area factors on water inflow is analyzed. The results show that the squeezing effect caused by blasting vibration makes the pore water pressure of surrounding rock around the tunnel rise rapidly in a short time. After reaching the peak value, it began to decline slowly with the weakening and disappearance of blasting vibration. Under the influence of damage zone factors, the water inflow of the tunnel increases gradually with the increasing thickness of the damage zone, but it will not increase continuously with the increase of the coefficient of permeability in the damaged area. Through numerical simulation calculation, the ratio of tunnel water inflow considering blasting damage area is 1.4, and the error is only 4.1% compared with the calculation result of 1.342 deduced in this paper. The calculated results in this study are only 0.53 m3 / (d · m) less than the field measured results, and are closer to the measured results than those with the traditional calculation formula, indicating that the calculation formula in this paper is suitable for the calculation of tunnel water inflow considering the factor of damage zone, and are of high engineering application value.
Geological suitability evaluation of underground space development in the Nanshan District of Shenzhen based on constraint conditions
ZHANG Xiaobo, LIU Kai, JIANG Peng, JIA Wuhui
 doi: 10.16030/j.cnki.issn.1000-3665.202206003
Abstract(2) HTML(1) PDF (4373KB)(0)
Urban underground space resource is one of the vital resources of the city. Shenzhen is the city with limited land resources and urgently needs to carry out geological suitability evaluation of underground space to guide the development and utilization of underground space. However, the development of underground space resource is restricted by a variety of geological factors. It is necessary to use appropriate methods to evaluate the geological suitability of underground space development. Taking the Nanshan District of Shenzhen as the study area, this paper proposes a constraint evaluation system that takes the constrained geological factors as the first-level evaluation index and combines the geological background of the study area with the planning of underground space resources utilization in Shenzhen. The geological suitability of shallow underground space (0−15 m) and sub-shallow underground space (15−30 m) in the study area of the conventional system and constrained system is evaluated by using the empirical score evaluation method and fuzzy comprehensive evaluation method. The results show that compared with the conventional evaluation system, the constraint evaluation system improves the overall weight of the constraint geological factors. According to the evaluation results of the constraint system, the poor and unsuitable areas are mainly distributed in the fault zone, high incidence of geological disasters and surface water area, which is more consistent with the actual geological conditions of the study area. Attention should be paid to the geological problems such as stratum instability and ground collapse caused by sand liquefaction in the unsuitable areas during the development and utilization of the key development zones in planning. Meanwhile, geological problems such as rock fragmentation and groundwater enrichment in the region of restricted active faults should be avoided reasonably. This study strongly supports the planning of underground space resource utilization in the Nanshan District of Shenzhen.
Study on the formation mechanism and resource development prospect of high-temperature geothermal system in Yanggao-Tianzhen area
HE Yadong, JIA Xiaofeng, ZHANG Zibin, SONG Jian, LIU Peisen, ZHANG Senqi, DUAN Jiangfei
 doi: 10.16030/j.cnki.issn.1000-3665.202302065
Abstract(2) HTML(1) PDF (7744KB)(1)
Under the background of “dual carbon”, Shanxi Province continues to promote the development of clean energy. In March 2020, high-temperature and high-pressure geothermal fluid was discovered near Shuitongsi Village, Tianzhen County, Datong. In order to explore the high temperature geothermal system and its genetic mechanism in Yanggao-Tianzhen area of Datong, an area of 20km2 in Gushan Village-Pingshan village of Yanggao County was selected as the key research area. Geological survey, geophysics, drilling, logging and other methods were used to find out the occurrence conditions and rules of geothermal in the study area. The results show that: (1) The geothermal resources in Yanggao-Tianzhen area are mainly hosted in the Archean metamorphic rocks and water-bearing rock formations in the fault zone. The direct heat source may be the uncooled magma chamber in the middle and upper crust, and the cover is the Quaternary accumulation, Neogene and Paleogene gravel layer. (2) The high temperature geothermal system in this area is convection and conduction geothermal system. On the one hand, atmospheric precipitation and surface water infiltrate into the thermal storage location through pore infiltration and fault fissure channels to form hot water. Then, it ascends to the shallow surface by convection along the fault channel and forms a hot spring. On the other hand, the continuous extensional environment since the Cenozoic has led to the upwelling of the asthenosphere. The basaltic magma formed by partial melting of the upper mantle rises to the middle and upper crust through deep fault channels to form multiple magma pockets. Heat is transferred to the shallow surface through faults or Archean metamorphic rocks with high thermal conductivity to form geothermal anomalies. (3) The pumping test results of YG-1 well show that, hydrothermal geothermal resources in this area are mainly static reserves, and non-interference heat exchange technology should be considered for development and utilization.Through comprehensive analysis of regional geological conditions, combined with geophysical prospecting and drilling results, it is believed that there may be dry-hot rock geothermal resources in the deep part of the region, which needs further investigation.
Study on simulation and optimization of production-reinjection scheme of geothermal water system: A case study of the geothermal space heating demonstration area in northern Jiangsu countryside
ZOU Pengfei, WANG Caihui, DU Jianguo, GE Weiya, LUO Zujiang, KONG Gang, QIU Yang, LIU Li
 doi: 10.16030/j.cnki.issn.1000-3665.202302046
Abstract(0) HTML(1) PDF (5859KB)(1)
During the process of developing and utilizing geothermal resources, various challenges are encountered. One such challenge is the decrease in temperature and pressure of the geothermal reservoir as a result of increasing geothermal exploitation and duration. Additionally, the discharge of geothermal tail water poses a risk of thermal pollution, leading to environmental concerns. To address these issues effectively, reinjection of geothermal fluids into the reservoir can be implemented as a viable solution. Prior to initiating geothermal development and utilization, it is crucial to conduct scientifical and rational planning of the layout of production and reinjection wells. This involves exploring optimal strategies for production-reinjection scheme that prevent premature thermal breakthrough and maximize the efficient utilization of geothermal resources, thereby extending the lifespan of the geothermal reservoir. The Fengpei Basin, a Cenozoic rift basin that has developed since the Paleogene period, exhibits a widespread distribution of geothermal reservoirs, primarily composed of Ordovician limestone with karst and fracture characteristics. Building upon the geothermal resource exploration results in Anguo Town, Peixian County, Jiangsu Province, this study utilizes key parameters obtained from pumping tests and reinjection experiments, such as well spacing and the reinjection-to-production ratio. This paper establishes a three-dimensional coupled numerical model of geothermal water seepage and heat transfer by using Feflow6.2 software. We simulate and predict the recoverable reserves of geothermal fluid within the geothermal reservoir, specifically focusing on the Ordovician limestone formation. Furthermore, a simulated optimization of the development and utilization scheme for production-reinjection wells is conducted. The research findings reveal that an appropriate well spacing of 389 meters between the producing well (RPX01) and the reinjection well (RPX02) is recommended. Moreover, the reinjection-to-production ratio, namely the ratio of average aquifer hydraulic conductivity, is determined to be 1.29, supporting a sustainable approach of one-for-one pumping and reinjection. With a stabilized drawdown at 50.61 m, the producing well has a capacity to recover 1000 m3/d of geothermal resources. Under the conditions of an production rate and reinjection rate of 1000 m3/d, as well as a reinjection temperature of 40 ℃, the simulation predicts a decrease in water level by 45.49 m and a temperature reduction of 1.44 ℃ after ten heating seasons. This represents the optimal cyclic development and utilization scheme among the simulated scenarios. The above results provide a scientific basis for decision-making in the construction of the clean energy heating demonstration area in rural northern Jiangsu. They contribute to the establishment of a scientifically sound and sustainable approach for utilizing geothermal resources, while considering the challenges associated with thermal breakthrough and the environmental impact of geothermal tail water discharge.
Triaxial creep test and model study of red sandstone based on Weibull distribution
ZHANG Weize, WANG Linqing, GUO Wenchong, CHEN Lei
 doi: 10.16030/j.cnki.issn.1000-3665.202211041
Abstract(2) HTML(1) PDF (4222KB)(1)
At present, the creep problem of underground engineering surrounding rock still exists, and the creep theory needs to be further enriched. In essence, rock creep is a process of constant accumulation of damage. In view of the damage evolution of rock under creep conditions, triaxial creep tests were carried out on red sandstone taken from Yibo Tunnel in Leshan, Sichuan Province by TAW-2000 to analyze the creep deformation rule of specimens under different confining pressures. Based on Weibull distribution and Perzyna viscoplastic theory, an improved viscoelastoplastic creep model is established which can describe the whole process of rock creep failure. The critical point damage variable is defined by dividing the creep stage, so that the acceleration creep start time can be determined more accurately. The following conclusions are drawn: (1) the model curve in this paper is in good agreement with the test data, which verifies the accuracy and rationality of the model in this paper, and indicates that the viscoelastic-plastic creep model of red sandstone established based on Weibull distribution is feasible. (2) Based on Perzyna viscoplastic theory, a more accurate viscoplastic strain expression is established to describe accelerated creep. (3) The relationship between rock creep deformation and damage can be better reflected by defining critical point damage variables at different creep stages in this paper, which makes up for the shortcoming that Nishihara model cannot describe accelerated creep and enriches the creep constitutive theory of rock materials.
Lithospheric thermo-rheological structure of Huangshadong geothermal field, Huizhou, Guangdong, and its heat-sources implications
GAN Haonan, LIN Wenjing, WANG Guiling, YAN Xiaoxue, YUE Gaofan, WENG Wei, ZHANG Delong
 doi: 10.16030/j.cnki.issn.1000-3665.202302054
Abstract(6) HTML(1) PDF (3996KB)(1)
The thermo-rheological structure of the lithosphere is an effective method to reveal the thermal state within the lithosphere. Studies on the thermo-rheological structure of the lithosphere in geothermal anomaly areas can effectively constrain the contribution of heat sources. The southeastern China is an important distribution region for geothermal resources, with a large number of natural hot springs exposed on the surface. Boreholes has identified high geothermal gradients at depth. However, the mechanism of the heat source is still controversial, and whether does the hot dry rock resources exist is not clear. In this study, we take Huangshadong geothermal field, Huizhou, Guangdong as the research target. We analyzed the temperature distribution and rheological strength of the lithosphere, discussed the heat sources of Huangshadong geothermal field, analyzed the thermal influence of shallow hydrothermal systems, and the prospects of dry hot rock resources. The results show that the heat flux under the influence of hydrothermal systems in Huangshadong geothermal field is 130.3 mW /m2, and the crustal heat flow is similar to the mantle heat flow, showing a warm-crust-warm-mantle lithospheric thermal structure. In addition, the structural heat flux reaches 30.5-60.3 mW/m2. The rheological structure of the lithosphere shows that the middle crust has a ductile rheological layer, the upper crust and the lower crust are mainly controlled by brittle failure, and the lower crust and the lithosphere mantle show coupling in rheological structure, which indicates a relatively stable crustal bottom boundary. The heat source of Huangshadong geothermal field is dominated by the tectonic heat source, and mantle heat source and radiogenic heat production are the main heat source components. The main parts of tectonic heat source include the heat accumulation in regional deep faults and cyclic heat transfer in hydrothermal systems, both of which may carry heat to the surface through "relay" heat transfer. The proportion of heat accumulation of regional deep faults in tectonic heat source is the key factor affecting the prospects of dry hot rock resources. This study offers the heat source reference for subsequent hot dry rock resource exploration and target site selection along the southeastern China.
High-level collapse risk identification based on oblique photography and InSAR technology
WANG Pengwei, AN Yuke
 doi: 10.16030/j.cnki.issn.1000-3665.202208068
Abstract(169) HTML(172) PDF (7520KB)(18)
Collapse risk identification is the basis of collapse disaster prevention. High level collapse is characterized by sudden, hidden and large height difference, which brings great challenges to information collection, disaster identification and risk assessment. In order to solve this engineering problem, this paper takes the Jiulongxia high slope in the Bailong River basin as an example, uses tilt photography to build high level collapse identification index and its structural plane information extraction method, proposes a collapse risk assessment model combining stereographic projection qualitative analysis and InSAR quantitative analysis, and forms a whole process model of high level collapse identification and risk assessment combining collapse identification, stability analysis and deformation monitoring. The results show that there are 22 collapse dangerous rocks in the study area (including 7 high risk rocks, accounting for 32%, 11 medium risk rocks, accounting for 50%, and 4 low risk rocks, accounting for 18%), with a distribution height of 37 m – 640 m. High risk dangerous rocks are mainly concentrated in the prominent mountain mouth in the south, the eastern slope and the western slope toe. These analysis results are consistent with the historical data of highway disaster maintenance, which verifies the feasibility of tilt photography and InSAR technology in high level collapse risk identification. The results provide a basis and reference for the application of this technology in collapse disaster prevention.
Calculation methods of the collapse influence range of a simple rock slope in the Guangzhou area
ZENG Qiqiang, WANG Lichao, LIU Wei, ZHANG Qinghua, CHEN Lingwei, LOU Kangming, LIU Yang, FAN Yanan
 doi: 10.16030/j.cnki.issn.1000-3665.202208053
Abstract(181) HTML(186) PDF (4475KB)(15)
The terrain and landforms of Guangzhou are complex and diverse, with developed economy and intensive human engineering activities. As a result, a large number of manually excavated slopes and dangerous rock masses have brought huge hidden dangers to local production and life. In order to accurately evaluate the impact range of slope dangerous rock mass, improve the prevention and control ability of slope dangerous rock mass disasters, and reduce the threat of collapse, it is urgent to improve the calculation models of the impact range of slope dangerous rock mass. Based on the investigation of dangerous rock mass in Guangzhou, this study summarizes the types and shape characteristics of common dangerous rock mass on slopes, and establishes a physical geometric modelling of the influence range of dangerous rock mass according to the classification, comprehensively considering the main influencing factors of the collapse movement process, such as slope friction, block collision, bounce, fragmentation, contact surface cover property and rebound coefficient, terrain conditions, earthquakes. A linear calculation model for the collapse impact range of curved slopes under different slope conditions is established, and the expansion coefficient of the collapse impact range under seismic conditions is obtained based on the influence of seismic peak acceleration on the kinetic energy of the collapse body. This model further summarizes the classification of slope shape based on previous researches, and provides a complete calculation model for the maximum impact range of dangerous rock mass on slopes under common terrain conditions and working conditions. After obtaining the slope height, slope, and surface characteristics, the impact range of dangerous rock mass can be calculated. Compared with the actual verification, the model results have relatively small errors while ensuring a certain safety distance, which can quickly and accurately evaluate the maximum impact range of common artificial slope dangerous rock masses, and provide a reliable basis for the prevention and control of slope dangerous rock masses.
A study of the capillary rise characteristics of LNAPL based on the vertical pipes method
LI Zhiping, LIU Yu, ZHAO Guizhang, ZHOU Hui, LIU Shaokang, LIU Wenhui
 doi: 10.16030/j.cnki.issn.1000-3665.202209020
Abstract(172) HTML(92) PDF (3714KB)(18)
The pollution caused by light non-aqueous phase liquid (LNAPL) and its derivatives, known as "industrial blood", in the process of mining, production and transportation, has become a common pollutant. At present, many researchers have carried out extensive researches on LNAPL pollution, but the researches on the migration and hairiness of LNAPL in soil is still insufficient. The purpose of this test is to study and analyze the capillary rise law of LNAPL in different media under different standpipe diameters through indoor simulation tests, so as to provide a certain theoretical basis for studying the groundwater pollution caused by LNAPL. The results show that the factors influencing the height of capillary rise are, in order, the solution > medium> vertical tube diameter. The diameter of the vertical tube is not completely proportional to the maximum capillary rise height, and the influence on the capillary rise height is relatively small. The capillary rise height and capillary rise rate of water and diesel in different media are basically the same, but there are differences in specific values. The maximum capillary rise height of diesel is 40%−50% lower than that of water, and the maximum capillary rise rate of diesel is 30%−50% lower than that of water. The average particle size of sand is inversely proportional to the capillary rise height and rate. These characteristics can better reflect the capillary rise law of LNAPL in different media, which are of important significance to understand the pollution of LNAPL to groundwater and the remediation of contaminated lands.
An analysis of the changes in groundwater balance elements of the Baoding Plain
JING Jiangnan, WANG Wenke, DUAN Lei, MA Jiajun, MA Zhitong, SHI Hanyue
 doi: 10.16030/j.cnki.issn.1000-3665.202208083
Abstract(5686) HTML(171) PDF (5121KB)(50)
With the implementation of the South-North Water Diversion Project and the implementation of groundwater suppression, the local groundwater levels in the North China Plain have gradually rebounded. However, there is a lack of systematic studies of the trends of groundwater balance elements and their impacts on the ecological environment. This paper takes the Baoding Plain, a typical area in the North China Plain, as an example, and uses the water balance method to calculate the groundwater recharge and discharge terms, applies the factor analysis method to analyze the causes of the changes in groundwater balance elements from 1975 to 2019, and calculates the amount of recoverable and suppressed groundwater resources by using the optimal exploitation coefficient method, so as to regulate the groundwater resources development and utilization in Baoding. The results show that in the past 40 years, the groundwater recharge term was smaller than the discharge term in the Baoding Plain, which is in a negative equilibrium state, and the main change elements are canal irrigation infiltration, canal system seepage, well irrigation return, river seepage, rainfall infiltration and artificial exploitation, with the decrease of 88.9%, 89.1%, 81.1%, 12.22%, 26.1% and 32.2%, respectively. The main factor affecting the change of groundwater equilibrium elements is human activity, with a contribution rate of 77.2%. After the groundwater recharge and discharge imbalance is slowed down, the increase of groundwater level burial depth becomes smaller, the area of groundwater level depression cone gradually decreases, and the area of the Baiyangdian wetland gradually recovers. The optimal exploitation coefficient of groundwater resources in the Baoding Plain is determined to be 0.64, the exploitable groundwater resources range from 8.89×108 to 11.35×108 m3/a, and the amount of compression exploitation ranges from 2.68×108 to 5.14×108 m3/a. The research results can provide technical guidance for groundwater extraction and utilization in similar regions, and also provide groundwater ecological environment protection for the construction of the Xiong’an New Area.
An early prediction model of regional landslide disasters in Fujian Province based on convolutional neural network
DONG Lihao, LIU Yanhui, HUANG Junbao, LIU Haining
 doi: 10.16030/j.cnki.issn.1000-3665.202211018
Abstract(2604) HTML(190) PDF (5679KB)(49)
Landslide disasters occur frequently in Fujian Province, and early warning of landslide disasters on a regional scale is an important means of effective disaster prevention and mitigation. Due to the complex mechanism of landslide disasters, the traditional regional landslide early warning methods have such problems as insufficient accuracy. Deep learning mainly refers to the technology of feature extraction, abstraction, representation and learning by constructing the neural network model, which is a kind of machine learning. As a classical deep learning algorithm, convolutional neural network has more powerful classification and representation ability than traditional machine learning. Taking Fujian Province as the research area, this paper introduces the convolution neural network into the field of landslide disaster early warning and constructs a regional landslide early warning model of Fujian Province. The process is as follows: ① the SMOTE optimization algorithm is used to optimize the sample database of landslide disasters in Fujian Province from 2010 to 2018, enlarging the number of positive samples and expanding the proportion of positive and negative samples from 1∶3.4 to 1∶2, and the total number of samples reaches 19151. ② Construct a convolution neural network model structure, which includes an input layer, two convolution layers, two maximum pooling layers, a full connection layer and an output layer. ③ Use the convolution neural network to train the optimized samples (80% of the samples from 2010 to 2018 as the training set), and use the Bayesian optimization algorithm to optimize the model parameters to obtain the regional landslide early warning model of Fujian Province. ④ The model is verified with 20% of the samples from 2010 to 2018 as the test set, and the confusion matrix and ROC curve are used to verify the model. The results show that the accuracy of the model ranges from 0.94 to 0.97, the AUC value is 0.975, indicating that the model accuracy and generalization ability are good. ⑤ The actual situation of the landslide disaster in the flood season of 2019 is taken as a positive sample, negative samples are collected through the method of time-space sampling, and the 2019 regional landslide sample verification set (603 samples) is constructed. The model is further verified by using the confusion matrix and ROC curve. The results show that the accuracy of the model ranges from 0.75 to 0.80, and the AUC value is 0.852. Although only the actual landslide samples in the flood season of 2019 is used for verification, good results is also achieved. In this paper, the convolution neural network algorithm is applied to the regional landslide early warning, which provides a new way to establish the regional landslide early warning model. The preliminary verification shows that the model is effective and will be further applied and verified in Fujian Province in the future.
The progress and prospects of potassium stable isotopes in hydrogeochemistry
JI Taotao, JIANG Xiaowei
 doi: 10.16030/j.cnki.issn.1000-3665.202301006
Abstract(2618) HTML(174) PDF (3430KB)(43)
Chemical weathering of silicate minerals is an important source for Ca, Mg, Na and K, however, in comparison with other major elements (e.g., Ca, Mg and Na) in waters, how K behaves during water-rock interaction remains poorly constrained. Recent studies have shown that large K isotopic fractionation could occur during various processes of low-temperature water-rock interaction, making K isotopes gradually become a powerful tracer for K elemental cycle. This overview summarizes (1) K isotopic compositions of major reservoirs at the Earth’s surface, including upper continental crust, hydrosphere and other reservoirs (plants and fertilizers), (2) the magnitudes and mechanisms of K isotope fractionation during common water-rock interaction processes (i.e., silicate dissolution, secondary mineral formation, adsorption, cation exchange), and (3) The latest studies that applied K isotopes to trace silicate weathering and water pollution. Based on the discussion above, we conclude with an outlook on future K isotopic studies in the field of hydrogeochemistry.
A discussion of the cause of land subsidence in the northeast of the Xiong’an New Area
YAN Xingguang, LU Zechang, ZHANG Jincai, ZHAO Weiling, CHEN Yong, LUO Hanmeng, CHU Lifeng
 doi: 10.16030/j.cnki.issn.1000-3665.202207019
Abstract(178) HTML(201) PDF (5700KB)(32)
In order to deeply study the main controlling factors of land subsidence in the northeast of the Xiong’an New Area and effectively slow down the rapid development trend of land subsidence, it is necessary to put forward targeted prevention and control countermeasures. In this paper, the layered monitoring points are taken as the research object. Core samples are used to carry out conventional tests, high-pressure consolidation tests and layered settlement observation. Based on the previous research results, the causes of land subsidence are discussed. The results show that the total thickness of the Quaternary loose layer in the study area is 412 m, and the thickness of the shallow layer is 170 m. The viscous soil accounts for 66.4%−80.2%. The structure is loose and the sand-clay interlayer alternates frequently, and the water release condition is good. The shallow viscous soil has finer particles, good sortability, large porosity, and more than 0.25 liquid index, showing a soft plastic and plasticable state. The dead weight compression coefficient ranges from 0.03 to 0.43, with an average value of 0.07. Compared with the deep soil, the shallow viscous soil is of stronger compressibility. The shallow cohesive soil layer is dominated by underconsolidation, normal consolidation and underconsolidation. The average OCR of a depth of 0−90 m is 0.55, and that of 90-280 m is 0.89. Plastic deformation and permanent settlement are easy to occur. From December 2020 to December 2021, the total subsidence of the strata above the Quaternary in the study area was 61 mm. Among them, the subsidence contribution of the shallow Quaternary unconsolidated layer at a depth of 0−160 m is the largest, which is 42 mm, showing the characteristics of plastic deformation. The subsidence contribution of the deep Quaternary strata at 160−415 m is 19 mm, which shows the characteristics of viscoelastic-plastic deformation. The plastic deformation of cohesive soil layer with low consolidation and high compressibility caused by the excessive exploitation of shallow groundwater is the main cause of serious settlement in this area.
A study of the kinematic characteristics and energy conversion of waves generated by granular landslide
WANG Jiajia, CHEN Hao, XIAO Lili, LI Zhiqiang, XU Xin, XIANG Yuheng, CHE Silu
 doi: 10.16030/j.cnki.issn.1000-3665.202207022
Abstract(141) HTML(213) PDF (5847KB)(34)
The consequences of landslide waves are far beyond the landslide itself that has attracted widespread attention. The prediction and evaluation of this kind of disaster has always been difficult, and the precise description of landslide surge motion characteristics and energy conversion law is the key and premise to solve the problem. In this paper, we use gravel to mimic granular landslide and establish a 3D landslide wave model in a rectangular flume, aiming to analyze how the landslide volume, velocity and water depth affect landslide accumulation, wave characteristics and energy conversion. The results show that (1) the waves generated by solid impacting the water are affected by the landslide size and shape. Slides with larger thickness and faster speed tend to produce nonlinear transition wave, and thin and slow slides generally produce nonlinear oscillation wave. (2) The volume effect and velocity effect based on the test reveal that the surge scale of a certain water depth is positively correlated with the landslide volume and velocity. The water depth effect explains the differences of waveform and velocity under a certain wave energy. Statistic results show that under the shallow water conditions, surge height on average is 67% higher and wave speed on average is 51.17% higher than those under the deep water conditions. (3) The conversion rate between landslide energy and wave energy ranges from 1.00% to 3.07%. 3D experiments encounter more energy dissipation due to diffusion and its conversion rate is lower than that in the 2D experiments. This study discusses the kinematic characteristics of granular landslide, first wave generation, propagation and inundation, and proposes the basic law of energy conversion between landslide and water. It id of certain value and significance for landslide wave hazard prevention and mitigation.
A study of the stability evaluation method of rainfall-induced shallow loess landslides based on the Maxent-Sinmap slope model
LIU Fan, DENG Yahong, MU Huangdong, QIAN Faqiao
 doi: 10.16030/j.cnki.issn.1000-3665.202207050
Abstract(226) HTML(194) PDF (10634KB)(34)
To address the problem of low evaluation accuracy of the Sinmap model in evaluating the stability of shallow loess landslides under the action of rainfall, a method based on the Maxent-Sinmap model is constructed to evaluate the stability of regional shallow rainfall loess landslides under the action of rainfall by improving the evaluation of the Sinmap model based on the maximum entropy model. Zhidan County, an area with a high incidence of loess landslides, is taken as an example. Relevant data on topography, geotechnical parameters and geological hazards are obtained by using field and indoor related work, and the main environmental variables are gained through the Maxent model to realize zoning. On the basis of these, the stability of shallow loess landslides under the action of rainfall is evaluated through the Sinmap model. The results indicate that the contribution of slope (27.1%), rainfall (20.3%), landform (18.8%), road buffers (18.7%) and vegetation cover (6.2%) to historical disaster sites within Zhidan County are obtained based on the Maxent model. Compared to the traditional Sinmap model, the density of unstable areas increases by 17.26% (light rainfall), 16.54% (moderate rainfall), 17.39% (heavy rainfall), 14.20 (rainstorm) and 12.96% (downpour), respectively. The results of the Maxent-Sinmap model have a larger stable area than those of the Sinmap model, and there is no historical disaster distribution in the expanded area of the stable area. The model has higher accuracy and more reliable results, which can provide a better scientific basis for the evaluation of regional shallow rainfall landslides.
A study of the critical groundwater level related to soil consolidation characteristics of land subsidence in Cangzhou
WANG Yunlong, CHEN Ye, GUO Haipeng, MENG Jing, WANG Haigang, ZANG Xisheng, ZHU Juyan
 doi: 10.16030/j.cnki.issn.1000-3665.202208040
Abstract(230) HTML(207) PDF (4194KB)(60)
Land subsidence has become a serious issue in Cangzhou for a long time. In order to make reasonable use of groundwater resources, it is necessary to establish a warning groundwater level under the premise of controlling the development of land subsidence. How to quantitatively determine the critical gorundwater level (CWL) for comprehensive control of land subsidence? In allusion to this scientific problem, this paper takes the soil samples of three typical settlement areas in Cangzhou as the research object, and analyzes the formation consolidation characteristics. By correlating the stratum thickness, we improve the method of calculating the CWL with the previous consolidation pressure. Based on the monitoring data of land subsidence and groundwater level in Cangzhou for many years, the comprehensive quantitative evaluation of the CWL in Cangzhou are carried out. The results are show that the soil within a depth ranging from 0 to 150 m in Cangzhou is normally consolidated or under-consolidated, and the soil below the depth of 150 m is generally over-consolidated. The inelastic water release deformation is an important factor affecting the change of land subsidence rate in this area. Using the improved method, the CWL in Cangzhou, Suning and Dongguang is 66.8 m, 67.2 m and 67.8 m, respectively. Based on the data of the cumulative land subsidence and groundwater level change in the urban of Cangzhou, we obtain the exponential function relationship between the cumulative land subsidence and groundwater level. The subsidence rate is taken as the index, and the critical groundwater level in Cangzhou ranges from 65 to 70 m. On the basis of verifying the consistency of the calculation results of the two methods, we determined 65 m as the critical groundwater level for the prevention and control measures of land subsidence in Cangzhou. The results provide a reliable basis for the local government to formulate a reasonable groundwater exploitation plan.
Abstract(289) HTML(813) PDF (2751KB)(522)
Characteristics of geological hazards and it’s mitigations of the Ms6.8 earthquake in Luding County, Sichuan Province
TIE Yongbo, ZHANG Xianzheng, LU Jiayan, LIANG Jingtao, WANG Donghui, MA Zhigang, LI Zongliang, LU Tuo, SHI Shengwei, LIU Minsheng, BA Renji, HE Longjiang, ZHANG Xinke, GAN Wei, CHEN Kai, GAO Yanchao, BAI Yongjian, GONG Lingfeng, ZENG Xiaowen, XU Wei
 doi: 10.16030/j.cnki.issn.1000-3665.202209029
Abstract(417) HTML(262) PDF (5917KB)(171)
On 5th September, 2022, the Ms 6.8 earthquake in Luding County, Sichuan Province induced large numbers of geological hazards. To deeply understands the evolution, distribution, and characteristics of geological hazards caused by the earthquake, we got the distribution of geological hazards by the field investigation and remote sensing interpretation. Then we analyzed the conditions for hazard control and the countermeasures for hazard prevention and reduction. The results show that as of 22:00 on September 14, 2022, the earthquake has induced 565 geological hazards with threat objects in Luding County and Shimian County (including 331 collapses and 234 landslides), and there were 81 existing geological hazards became more deformed. The types of geological hazards induced by the earthquake are mainly medium and small mass high-level collapses, which are mainly concentrated in the areas with Seismic intensity zone ofⅨ near the epicenter. These areas include Moxi Town, Detuo Township, both banks of Dadu River between Detuo Township and Dewei town in Luding County, Caoke Township and wanggangping Township in Shimian County. According to the experience of the Wenchuan earthquake, the debris flow will be active in the next five years, and its characteristics of high frequency and viscous debris flow should be considered in the design of debris flow prevention and control engineering. Under the rainfall condition, the landslide deposition remaining on the slopes of Dadu River banks in the section of Detuo Township Dewei town can be easily transformed into debris flow. It is suggested that the transformation forms of the two hazards’ types should be fully considered in the design of prevention and control projects. The study can provide a reference for earthquake geological hazard prevention and post hazard reconstruction planning in the earthquake area.
Display Method:
2023, 50(3): 1-2.  
Abstract(169) HTML(146) PDF (334KB)(32)
Mineral compositions and microstructural characteristics of the tight sandstone reservoir in the Sulige area and their potential influence on hydraulic fracturing
LI Peiyue, HE Xiaodong, ZHOU Changjing, XIE Yonggang, SHI Hua
2023, 50(3): 1-11.   doi: 10.16030/j.cnki.issn.1000-3665.202211048
Abstract(6448) HTML(143) PDF (10098KB)(77)
Tight sandstone gas is an important unconventional natural gas resource. Mineral characteristics of the tight sandstone not only affect the occurrence of gas, but also have a significant impact on the hydraulic fracturing effectiveness. The potential influence of tight sandstone mineral compositions and microscopic morphology on gas reservoir during hydraulic fracturing was seldom examined. In this study, five tight sandstone gas wells in the Sulige gasfield located in the Ordos Basin were drilled. The core samples of the 8th formation of the lower member of the Permian Shihezi Group (He 8) were collected. The mineral characteristics, microstructure and pore feature of the tight sandstone are systematically analyzed by using XRF, XRD, casting thin section, SEM and EDS technologies and the potential effects of the above factors on hydraulic fracturing are discussed. The results show that the tight sandstone is mainly composed of lithic sandstone and lithic quartz sandstone. The density of the tight sandstone ranges from 2.44 to 2.56 g/cm3, the porosity from 7.7% to 12.6%, and the permeability from 0.16 to 1.42 mD. The mineral compositions are mainly quartz and clay minerals (16.5%−47.4%), and feldspar and carbonate are absent. Kaolinite, illite and chlorite are the main clay minerals. Kaolinite is widely developed, filling the intergranular pores and surface in the forms of “booklets” and worm-like. The intergranular pores, intragranular solution voids, intergranular and intragranular fractures occur in the tight sandstone, which provide basic reservoir space for natural gas. The results of mineral analysis and fracturing fluid-tight sandstone interactions reveal that the stability of clay minerals, especially kaolinite and illite, are crucial for hydraulic fracturing in the Sulige gasfield. It is necessary to understand the mineral compositions and formation water of the tight reservoir and select the appropriate clay stabilizer to optimize hydraulic fracturing.
Research on the characteristics of water transport in the aeration zone of loess tableland
WU Weijiang, SONG Binghui, LIU Di, AN Yapeng
2023, 50(3): 12-22.   doi: 10.16030/j.cnki.issn.1000-3665.202208008
Abstract(3283) HTML(198) PDF (8412KB)(62)
There are abundant phreatic water in loess tablelands in the Loess Plateau of northwest China. The vertical infiltration of atmospheric precipitation is the main source of the recharge, but the spatial channels of water occurrence and migration in loess are still ambiguous. Based on the geomorphology, strata structure and other hydrogeological conditions, groundwater utilization condition and related experimental data of the Dongzhiyuan and Weibei loess tablelands, combined with scanning electron microscope image processing and statistical analysis, the pore characteristics and the migration processes of water in the loess phreatic and aeration zones are discussed and zoned. Pores are considered to be the main space channel for the occurrence and migration of loess groundwater, and the minimum equivalent pore size of seepage is about 12 μm. The vertical structural combination of the loess aeration zone composed of the Malan loess with developed pores in the upper part is conducive to the infiltration of atmospheric precipitation, and the water migration in the pores of the aeration zone is very weak and slow, but is relatively continuous and uniform. The aeration zone can be divided into four zones for loess: the climate impact zone, storage regulation zone, slow runoff zone and capillary receiving zone. Except for the upper climate impact zone, the other three zones are in a basically dynamic equilibrium state of water transport. The research results can provide important references for comprehensively and systematically understanding the characteristics of water transport in the aeration zone of loess tablelands.
Spatial variability of free porosity in the groundwater level fluctuation zone in the Baoding Plain area
XU Buyun, YANG Huifeng, BAI Hua, SONG Bo, MENG Ruifang
2023, 50(3): 23-33.   doi: 10.16030/j.cnki.issn.1000-3665.202208004
Abstract(2162) HTML(401) PDF (6520KB)(90)
Scientific determination of geological parameters of the groundwater level fluctuation zone is an important step for water resources evaluation and management. In the past 40 years, over-exploitation of groundwater in the Baoding Plain led to a serious deficit of aquifers, thus forming a huge deep vadose zone. After the South-to-North Water Diversion Project was put into operation, with the progress of ecological water supplement of rivers and lakes and groundwater limited-over-exploitation, the groundwater levels in some areas of the Baoding Plain stopped falling and rose. The quantitative relationship between the amount of water supplement and the change of groundwater levels has become an important scientific issue in the management of over-exploitation of groundwater. However, under the condition of groundwater level recovery, the calculation results will be deviated if the specific yield parameter of water release process is still used. Therefore, the free porosity parameter study of groundwater level recovery process is the key to solve this problem. Based on 67 engineering geological boreholes in the Baoding Plain, the comprehensive free porosity during groundwater level recovery is determined according to the lithologic characteristic parameters of the groundwater level fluctuation zone. The semi-variogram model is selected by the trend analysis and cross validation, and the spatial unknown points are interpolated by the Ordinary Kriging interpolation. The results show that (1) the best semi-variogram model of the comprehensive free porosity in the groundwater level fluctuation zone of the Baoding Plain is the 1 order index model. The spatial autocorrelation of the data is obvious, which is mainly affected by structural factors such as spatial location of the groundwater level fluctuation zone and stratigraphic type. (2) The comprehensive free porosity distribution shows that the southwest and northwest are the high value areas, and the extreme value can reach 0.25. The parameter gradually decreases to the central and eastern regions, and the minimum value is 0.02. (3) Compared with the value of the conventional specific yield, the value of the free porosity increases by about 0.03 in the north and south regions, which is about 1.2 times that of the conventional specific yield. In the central region, it is reduced by about 0.06, which is about half that of the conventional specific yield value. The research results are of important research value and great significance for ecological water supplement and water resources regulation in the benefited regions of the South-to-North Water Diversion Project.
Study on the spatial vriability of hydraulic conductivity of underground reservoir in Fuping section of Shichuan River
WANG Jiling, ZHOU Weibo, SUN Lili, WANG Yimeng
2023, 50(3): 34-43.   doi: 10.16030/j.cnki.issn.1000-3665.202206021
Abstract(306) HTML(409) PDF (3695KB)(127)
The study on the spatial variability of hydraulic conductivity is the basis for artificial recharge of groundwater reservoir. In order to study the spatial variability of the hydraulic conductivity of underground reservoirs in Fuping section of Shichuan River, Box-Cox transform and Johnson transform were introduced to preprocess the field double-loop percolation test and exploration hole data. Traditional statistical methods and geostatistical methods were applied to analyze the hydraulic conductivity of the reservoir area with the variation function as a tool. The results show that the hydraulic conductivity of the reservoir area varies from 0.02 m/d to 6.44 m/d and obeys both logarithmic normal distribution and Box-Cox transformation normal distribution, the spatial correlation of the hydraulic conductivity is medium, and the best fitting model is Gaussian model. The Kriging interpolation results based on the optimal model show that the hydraulic conductivity as a whole is larger in the northwest and smaller in the southeast. The hydraulic conductivity is the largest near Meijiaping Township and Nanshe Township, ranging from 2.84 m/d to 6.44 m/d, with small spatial variation scale. It varies significantly near Mizi Township and Zhuangli Township, with large spatial variation scale. It is the smallest in the south of Dongshangguan Township, all less than 0.2 m/d, with small variation scale. The spatial variation is influenced by the combination of topography, geomorphology, distribution of stratigraphic lithology, hydro-meteorological conditions, distribution of test sites and exploration sites, human activities and other factors. The location of recharge should be chosen in Meijiaping town and other locations with large hydraulic conductivity, small spatial variation scale and low influence by human disturbance. The research results can provide theoretical references for the construction of underground reservoirs.
Influence of stratified heterogeneity on the recharge from surface water to groundwater
WU Peipeng, SHU Longcang, LI Fulin, CHEN Huawei
2023, 50(3): 44-53.   doi: 10.16030/j.cnki.issn.1000-3665.202208065
Abstract(3559) HTML(176) PDF (5829KB)(49)
Knowledge of the recharge from surface water to groundwater is the basement of the scientific understanding of water cycle and the sustainable management of groundwater resources. Meanwhile, the layered heterogeneity is the main structural feature of riverbed sediments (i.e., the lithologic difference between riverbed sediments and the underlying aquifer) and the main factor that controlling the recharge from surface water to groundwater. To reveal the influence mechanism of layered structure of pore media on the recharge from surface water to groundwater, a conceptual model of surface water and groundwater interaction is established based on the field test results of Henan reaches of the Yellow River, and the process of the recharge from surface water to groundwater interaction is described using flow path as the object. The results show that the exchange flux of surface water and groundwater is mainly affected by hydraulic conductivity of riverbed sediments, and the change of the thickness of riverbed sediments has little effect on the exchange flux between surface water and groundwater. That is, the increase of the ratio of the thickness of the sediments to that of the underlying aquifer (HS/H) from 0 to 0.125 leads to the interaction flux decreased by 72%, indicating that the existence of the low permeability layer is the main reason that decreases the interaction flux between surface water and groundwater. The change of the permeability and the thickness of riverbed sediments has obviously changed the flow path from surface water to groundwater and the travel time. Specifically, the increase in KU/KL leads to a lager penetration depth of groundwater flow and lager travel times. The sensitivity of exchange flux between surface water and groundwater and groundwater travel time to the hydraulic conductivity of riverbed sediments increases with the decreasing hydraulic conductivity. At the same time, the groundwater travel time is more sensitive to the change of the thickness of the low permeability riverbed sediments, and the sensitivity increases with the increasing thickness. The research results can provide reference for groundwater resource management and sustainable development.
Spatio-temporal change characteristics of water conservation function in the Zhang-Cheng district based on the InVEST model
MA Jingxuan, JIN Xiaomei, ZHANG Xucai, YIN Xiulan, JIN Aifang
2023, 50(3): 54-64.   doi: 10.16030/j.cnki.issn.1000-3665.202208084
Abstract(3961) HTML(211) PDF (6065KB)(55)
As one of the important ecosystem service functions, water conservation function is of great significance to the ecosystem and water safety in the Zhangjiakou and Chengde districts. Based on the integrated valuation of ecosystem services and tradeoffs (InVEST) model, this study quantitatively evaluates the water conservation function and analyses its driving factors of the Zhang-Cheng district from 2001 to 2020 using high-quality remote sensing data and other reanalysis products, in order to improve the problems of insufficient consideration of topography and soil permeability, as well as the inadequate analyses of data spatial heterogeneity in previous studies. The results show that the spatial distribution of the water conservation function in the Zhang-Cheng district from 2001 to 2020 was characterized by high values in the Baxia areas and low values in the Bashang areas. Despite some differences, the spatial distribution of the water conservation function in each year had some similarities to some extent. In terms of the trend, the water conservation depth in these 20 years showed a fluctuating downward trend with an average rate of −0.08 mm/a. Combined with the Sen+Mann-Kendall analysis, the trend of the water conservation function in this area was mainly classified as "No trend", "Slight increase" and "Slight decrease", accounting for nearly 98% of the total area. The results of correlation analysis show that precipitation had a strongly significantly positive correlation with water conservation function, temperature had a significantly negative correlation with water conservation function in some areas, and the correlation between vegetation and water conservation function was complex. In the Zhang-Cheng district in 2020, the woodland had the strongest water conservation function, and the water conservation depth reached 28.64 mm. On the other hand, the grassland water conservation function had the greatest contribution in the total amount, and the water conservation reached 1.12×109 m3. During these 20 years, the water conservation of the farmland had the most obvious decrease, with a rate of −6.49×106 m3/a. The spatio-temporal change characteristics of water conservation function in the Zhang-Cheng district in these 20 years were mainly controlled by precipitation and vegetated land use. This study provides an important decision-making basis for ecological construction and water resources management in the Zhangcheng district.
Prediction of mine water inflow and analyses of its influence on desert vegetation
LIU Mou, WANG Junjie, WU Guangtao, ZHOU Jie, LUO Qibin, KANG Weidong
2023, 50(3): 65-75.   doi: 10.16030/j.cnki.issn.1000-3665.202104015
Abstract(2670) HTML(199) PDF (5732KB)(34)
Mine inflow threats mine safety production underground, and may trigger a decline in the groundwater level in the mine area, causing irreversible successional degradation of surface vegetation. In view of the key problems such as inaccurate generalization of boundary conditions and unreliable selection of hydrogeological parameters when constructing numerical models of water inflow, this study aims to accurately predict mine water inflow, ensure the safe mining of coal seams, and provide theoretical and data support for the protection of desert vegetation in the study area. The natural boundary is selected as the perimeter of the research area, and the model is repeatedly revised on the basis of fully collecting and analyzing the data of drilling, geophysical prospecting, pumping test, groundwater long-term monitering, and the scope of the mine goaf and its water inflow, and thus a more realistic three-dimensional unstable flow numerical model of groundwater is constructed. In addition, the model simulation and identification are carried out according to the expansion process of the mine goaf and its water inflow and groundwater monitoring data, which demonstrates the rationality and reliability of the model. The established numerical model is used to predict the mine inflow and submersible level depth drop under coal seam mining conditions, and then the influence of diving level decline on desert vegetation is analyzed based on the relationship between diving depth and desert vegetation. The results show that the predicted water inflow in the mine is 3.08×104 m3/d, resulting in a decrease of 2.08−2.35 m in the diving level in the mine area, which will lead to the deterioration or even partial withering of the representative vegetation sand willow and poplar in the mine area, showing a succession trend from mesophytic vegetation type to xerophytic vegetation. The results can provide more accurate water inflow prediction in the study area, scientific and effective measures for the protection of desert vegetation in mining areas, and reliable treatment ideas for the construction of similar numerical models of groundwater flow.
Calculation method of thrust force of the embedded stabilizing piles under the overtop-sliding failure mode
YAN Yuping
2023, 50(3): 76-84.   doi: 10.16030/j.cnki.issn.1000-3665.202211007
Abstract(3348) HTML(203) PDF (4032KB)(56)
Embedded piles act as an optimization structure compared with the traditional stabilizing pile. The determination of the thrust on the loading section is based mainly on the model test and numerical simulation, and there is a lack of in-depth theoretical analysis. For the bedrock-talus landslide reinforced by embedded piles, according to the potential overtop-sliding failure mode, the slide surface can be divided into top and bottom sections by the position of pile top, and the horizontal resultant force of the top section can be obtained by integration, which is the so-called thrust of the embedded section. Similarly, the force on the bottom section of the overtop-sliding surface can also be obtained. Based on the limit equilibrium theory, the force analysis of the sliding mass enclosed by the bottom sliding surface and the load section of the pile can be carried out, and the thrust on the loaded section can also be obtained. Example analyses show that the thrust of the embedded section and the loaded section obtained by the theoretical method are very consistent with the results of FLAC3D, the resultant force of the loading section decreases nonlinearly with the increase of the ratio, while the resultant force of the embedded section presents an opposite trend. With the increase of the embedded ratio from 0 to 0.67, the thrust ratio of embedded section and loading section increases slowly from 0 to 0.3−0.5. With the increase of embedded ratio from 0.67 to 0.8, the ratio increases sharply to 1.47−2.12. Generally, the thrust of embedded section is less than that of loaded section. The theoretical research of the thrust of the embedded pile is of great practical significance for the optimization of the pile internal force and the determination of the pile embedded depth, which will promote the further application of this structure.
A uniaxial compression damage model for rockmass considering the crack deformation parameter
LIU Hongyan, ZHANG Guangxiong, ZOU Zongshan, HE Tiezhu
2023, 50(3): 85-92.   doi: 10.16030/j.cnki.issn.1000-3665.202208017
Abstract(2705) HTML(136) PDF (3385KB)(58)
In order to accurately predict the effect of crack on the rockmass compression mechanical property such as strength and stiffness, a more reasonable compression damage model for the cracked rockmass is needed to be established. On basis of the relevant experimental data and mechanical behavior of the cracked rockmass under uniaxial compression, some deficiencies in the existing compression damage models for the rockmass with intermittent cracks are analyzed in detail. Three improvements are made to improve the existing methods, e.g., the crack deformation parameter is not taken as a constant, the negative first stress intensity factor KI produced by the normal stress on the crack face is considered, and KI produced by the effective shear stress on the crack face is considered. A revised uniaxial compression damage model for rockmass considering the crack deformation parameter is proposed and the validity of the proposed model is verified with the experimental data. The results show that the prediction of the rockmass elastic modulus and damage under uniaxial compression with the proposed model are more accurate than those obtained with the existing models. Especially, when the crack dip angel is 0°, the rockmass elastic modulus obtained with the proposed model is 4.306 MPa, which is nearly equal to its tested value 4.310 MPa. The proposed model can perfectly describe the rockmass mechanical behavior under uniaxial compression, which also indicates that it is very necessary to consider the effect of the crack deformation parameter on the rockmass uniaxial compression mechanical property. This study can provide references for accurately predicting the rockmass mechanical behavior under uniaxial compression.
Effect of Cu2+ on the saturated coefficient of permeability of remolded loess
JIA Yang, CUI Suli
2023, 50(3): 93-103.   doi: 10.16030/j.cnki.issn.1000-3665.202201042
Abstract(161) HTML(150) PDF (4449KB)(43)
The coefficient of permeability is an important index to evaluate the migration and diffusion of heavy metal polluted liquid in remodeled loess. At present, the existing studies have shown that there is a certain correlation among the pH value, the value of electrical conductivity, ion content and saturated coefficient of permeability of the polluted liquid, but the geochemical reaction mechanism during the infiltration process has not been clarified. Therefore, the Qp loess in the Bailuyuan area of Xi’an is collected, and the Cu2+ solution is selected as the infiltration solution to carry out the saturated infiltration test of the reshaped loess, and the geochemical inversion model based on the Netpath software is established. The results show that the saturated coefficient of permeability decreases significantly from the first day during the test, and has a larger decrease compared with the deionized test group, with a range of 5.57×10−5 cm/s. The ion source analysis proves that the geochemical reaction occurs, including mineral dissolution, precipitation and cation exchange. The geochemical inversion simulation results show that the presence of Cu2+ aggravates the mineral dissolution and produces a large amount of Ca2+, which promotes the leftward shift of the carbonate mineral dissolution balance, starting from the first day continual calcite and dolomite precipitation, and the precipitation amounts are 1.912 mmol and 0.958 mmol, respectively, which blocked the seepage pores and reduced the coefficient of permeability of the soil. The results are helpful in understanding the change of the saturated the permeability coefficient of the remodeled loess during the intrusion of heavy metal ions, and are of important theoretical significance for further clarifying the geochemical mechanism affecting the change of the permeability coefficient.
Application of seepage analyses based on Fredlund & Xing model in red beds terrace landslides in eastern Sichuan
LIAO Yong, LE Jian, HU Li, GU Weiwei, XU Jinxing
2023, 50(3): 104-114.   doi: 10.16030/j.cnki.issn.1000-3665.202202049
Abstract(4634) HTML(158) PDF (8396KB)(53)
The Shuitoushang landslide in Ershe in Qijiagou Village of Xinchang Town in Tongjiang County is a typical red-bed terrace landslide in eastern Sichuan. There are few studies on the seepage analyses of such landslides in this area, but similar slopes are widely distributed in the area. In this paper, on the basis of a large number of field investigations, surveys and data collection of disaster sites, the satellite remote sensing, UAV aerial photography, airborne LiDAR, indoor tests and other technical means are comprehensively used to analysis the landslide. Based on the mathematical model of Fredlund & Xing soil-water characteristic curve, the SEEP/W module in Geo-Studio is used to conduct the seepage analysis, and the analysis results at different time stages are coupled with the SLOPE/W module. Then the dynamic relationship between the stability coefficient, rainfall and time is obtained, revealing the deformation process and formation mechanism of the landslide. The results show that: (1) the continuous rainfall causes the groundwater level to rise and the slope stability to decrease, eventually leading to the overall instability and failure of the Shuitoushang landslide. (2) The deformation process of the landslide and the characteristics of groundwater exposure are basically consistent with the results calculated by Geo-Studio, indicating that the results based on Fredlund & Xing model can provide more accurate simulation results in similar areas. (3) Reclamation of terraced fields (paddy fields) will reduce slope stability. The results can provide theoretical support for hidden danger investigation and active prevention of similar landslide disasters in mountainous areas of Sichuan, and provide a reference for disaster prevention and mitigation.
Influence mechanism of vegetation infiltration effect on shallow landslides of granite residual soil
CHEN Jingye, WANG Jun, GONG Qinghua, YUAN Shaoxiong, XU Anze, LUO Yizhen
2023, 50(3): 115-124.   doi: 10.16030/j.cnki.issn.1000-3665.202205054
Abstract(6816) HTML(389) PDF (5515KB)(61)
The landslides induced by typhoons and rainstorms in Southern China are often shallow, fluidized and clustered. A large number of investigations have shown that vegetation infiltration has a significant impact on the formation of granite residual soil landslides. However, most of the current studies have focused on the effect of vegetation roots on soil infiltration. The influence mechanism of vegetation infiltration enhancement effect on shallow landslides has not been revealed. Therefore, the mass landslide disaster on September 9, 2019 in Longchuan County in Guangdong is taken as an example, and a large number of landslide site investigations are made to identify the geological environment conditions and vegetation development in the landslide area and analyze the infiltration effect of vegetation on shallow landslides. The “double-ring method” is used to measure infiltration rate of different vegetation types, and to analyze the infiltration process and infiltration law of different vegetation types. A typical landslide profile is selected to establish a geological model, and the Geo-Studio software is used to simulate the seepage law of shallow landslide and the stress-strain characteristics of the soil under heavy rainfall conditions (250 mm/d). Finally, combined with the simulation results and field investigations, the infiltration effects of vegetation and their response mechanisms to shallow landslides under heavy rainfall are analyzed. The results show that vegetation can effectively enhance the permeability of soil, and the order of permeability is coniferous forest land, shrub forest land and bare land. Under the influence of vegetation infiltration effect, rainwater infiltration to the bottom of the root-soil composite layer will cause water stagnation, the shallow soil tends to be saturated rapidly, the pore water pressure and seepage force in the soil increase instantaneously, the soil is saturated with water, the residual soil softens, and the weight of the slope increases, which eventually leads to the overall instability of the slope. The research results explain the formation mechanism of granite residual soil landslide in high vegetation covered area under heavy rainfall in Southern China, and provide scientific basis for early warning and prediction of such disasters, which are of great significance.
Landslide susceptibility assessment based on the SOM-I-SVM model
JIA Yufei, WEI Wenhao, CHEN Wen, YANG Qingzhuo, SHENG Yifan, XU Guangli
2023, 50(3): 125-137.   doi: 10.16030/j.cnki.issn.1000-3665.202206041
Abstract(6459) HTML(1943) PDF (8077KB)(93)
When using machine learning models for landslide susceptibility evaluation, the non-landslide sample points are usually selected randomly outside the landslide influence area, leading to a certain error. To improve the accuracy of landslide susceptibility evaluation, this paper couples the self-organizing map (SOM) neural network, information (I) model, and support vector machine (SVM) model, and proposes a SOM-I-SVM model-based method of landslide susceptibility evaluation, comparing with K-means clustering to verify the reliability of this model. The Maojian District of the city of Shiyan is taken as an example, and seven factors of the distance from water system, slope, rainfall, distance from structure, relative height difference, distance from road, stratigraphic lithology are selected by correlation and importance analyses of environmental factors to establish a landslide susceptibility evaluation system. Based on these, the graded information values of each factor are calculated and used as input variables for landslide susceptibility evaluation. The SOM neural network and K-means clustering are used to select non-landslide samples, and the sample data set is substituted into the I-SVM model to predict landslide susceptibility. The prediction accuracies of the four models, SVM, I-SVM, KMeans-I-SVM and SOM-I-SVM, are compared, and the area under the ROC curve (AUC values) are 0.82, 0.88, 0.90 and 0.91, indicating that the SOM-I-SVM model can effectively improve the accuracy of landslide susceptibility prediction.
A simulation study of the activity characteristics and genetic mechanism of coupled ground fissures: Exemplified by the Songzhuang ground fissure in Beijing
MENG Zhenjiang, PENG Jianbing, LI Chao, QIAO Jianwei, WANG Feiyong, KANG Chenyun, ZHAO Junyan, ZHANG Fan
2023, 50(3): 138-148.   doi: 10.16030/j.cnki.issn.1000-3665.202210038
Abstract(4114) HTML(190) PDF (8788KB)(60)
The active characteristics and genetic mechanism of coupled ground fissures mainly induced by fault activities and pumping are studied, and the Songzhuang Town in Tongzhou District of Beijing is taken as the research archetype. The damage of surface planes and stratigraphic profiles caused by ground fissure activities are clarified through field investigation, and the variation characteristics of the displacement field and stress field of the strata caused by different dislocation amounts and groundwater level drop are revealed. The response processes of the model stratum under the two conditions of fault misalignment and groundwater extraction are simulated and studied respectively by using the finite difference method. Finally, the relationship between this type of ground fissure and the main inducing factors is discussed. The results show that (1) the ground fissure is characterized by three-dimensional activities, which causes the vertical tension of the shallow stratum and wall to be 0.3−1.2 cm, and the vertical dislocation of the deep stratum gradually increases with the burial depth. (2) Stress changes caused by fracture activities are concentrated in the ground fissure development area and lead to significant vertical displacements in the hanging wall, the stratum located in the ground fissure area has large shear and traction deformation, and the vertical displacement difference between the two sides is the largest. The gradual increase of fault dislocations causes the hidden fractures to extend upward, and cause secondary cracks on the shallow surface of the hanging wall, resulting in the overall distribution of ground fissures with a certain width. (3) The vertical extension and horizontal expansion of ground fissures are aggravated by the lowering of groundwater levels, and the surface on both sides of the crack produces continuous settlement response, making the center of the subsidence funnel become a concentrated development area of ground fissures, with the maximum settlement of 10.2 cm in the model stratum at the fissure in its central area, and the settlement range of about 38 m in the hanging wall and about 16 m in the foot wall. (4) This type of ground fissures is obviously controlled by faults, but the increased activity in this period is mainly due to groundwater over-exploitation. This work will be of great theoretical and practical significance to understand ground fissure mechanism, establish quantitative relationship between formation and fault with groundwater, and prevent and reduce disasters.
A study of the tunnel collapse mechanism based on the BP neural network inversion analysis
CHEN Hang, ZHANG Beibei, KUANG Huajiang, XIAO Lina
2023, 50(3): 149-158.   doi: 10.16030/j.cnki.issn.1000-3665.202208066
Abstract(6697) HTML(498) PDF (4667KB)(184)
Tunnels in karst areas are prone to collapse during construction. There are many analyses on the mechanism of tunnel collapse in mechanical aspects, but the mechanism of tunnel collapse in karst weak fracture zones and other strata were seldom examined. In order to ensure the safety, economy and feasibility of tunnel construction, it is necessary to master the mechanism of collapse in the tunnel construction. Relying on a tunnel project in a karst broken stratum in Guizhou, where the collapse phenomenon occurred during the excavation process, the monitoring data of the tunnel are examined, and the construction principle of the BP neural network is used to invert the stratum parameters of the tunnel. The inversion soil mechanical parameters are input into different construction models constructed by using the FLAC3D finite element software, and the collapse failure mechanism and risk of typical sections are judged and analyzed. The results show that the construction method has a great influence on the stability of the tunnel excavation, and for the tunnel with the surrounding rock grade V , the three-step seven-step method and the single-side wall pilot pit method are safer for construction, and the tunnel collapse has no relationship with the simultaneous excavation of the tunnel in both directions. The predicted value of the tunnel vault displacement obtained by the inversion is 2.3 cm, and the predicted value of the surface displacement is 1.2 cm. The deviation from the monitoring data is about 13%, and the inversion result has certain reliability. The research results are of important guiding significance for the construction of tunnels and highways in weak and broken strata in karst areas.
Spatial distribution and sources of PAHs in topsoil in the Beiyun River Basin (Beijing section)
HUANG Dan, HUANG Yong, AN Yonglong, FENG Hui, SUN Zhao, LI Huan
2023, 50(3): 159-171.   doi: 10.16030/j.cnki.issn.1000-3665.202112022
Abstract(5140) HTML(190) PDF (6247KB)(62)
Organic pollution of polycyclic aromatic hydrocarbons (PAHs) in topsoil has threatened human health and ecological environment. In order to understand the distribution and pollution characteristics of PAHs in topsoil in the Beiyun River Basin in Beijing, an investigation is carried out to examine the contents, distribution trends, spatial distribution and pollution sources of 16 optimal PAHs in topsoil of the study area by means of multivariate statistical methods including the Kriging interpolation, principal component analysis-multiple linear regression and the concentration ratio among certain components. The results are as follows (1) all 16 PAHs are detected, and most of them are high loop PAHs (4−6 rings). The total contents of PAHs in topsoil range from 10.5 to 19466.5 μg/kg, about 29.63% of the samples are polluted in the study area. (2) The PAHs contents in topsoil show a trend of higher in the middle and lower at ends in both east-west and south-north direction. In terms of spatial distribution, the PAHs contents in topsoil are higher in the northern region and the central urban area, while the PAHs contents are lower in other areas. Due to the accumulation of PAHs caused by human activities at some points, point source pollution or local pollution exist. (3)The ratio of specific PAHs components and principal component analysis indicate that the sources of 16 PAHs in the study area are mainly coal, biomass combustion and traffic combustion. Multiple linear regression shows that the contribution rates of the two are 89% and 11% respectively. The research results can provide strong support for pollution prevention and control, land quality evaluation and territorial space planning in the study area.
Spatio-temporal variation of vegetation and its correlation with soil moisture in the Yellow River Basin
GAO Mengmeng, LI Xiaolei, YANG Nan, WANG Yi, LIU Qiong, ZHAO Zixin
2023, 50(3): 172-181.   doi: 10.16030/j.cnki.issn.1000-3665.202108051
Abstract(1773) HTML(189) PDF (6090KB)(40)
Analyzing the temporal and spatial changes of vegetation and its correlation with soil moisture and quantitatively revealing the impact of soil moisture on vegetation growth are of certain significance for drought monitoring and ecological protection. However, previous quantitative researches on soil moisture and vegetation growth are not enough. Based on MOD13Q1 NDVI products and global land data assimilation system (GLDAS) soil moisture data, Sen + Mann Kendall trend test and correlation analysis are used to analyze the temporal and spatial variation characteristics of vegetation and the impact of land use change on vegetation growth in the Yellow River Basin from 2000 to 2020. The correlation between vegetation and soil moisture at different depths in growing season is explored. The results show that (1) the vegetation growth is characterized by “high in the south and low in the north”. Along the runoff direction of the Yellow River, the vegetation growth on the right bank of the upper reaches is significantly better than that on the left bank, and there is no significant difference in the vegetation growth on the two banks of the middle and lower reaches. The NDVI increases by 22.19% from 2000 to 2020, with the highest value of 0.435 and the lowest value of 0.356. (2) The order of NDVI value of different land use types from large to small is woodland>cultivated land>grassland>unused land. The order of NDVI value of different seasons from large to small is summer>autumn>spring>winter. (3) Most of the vegetation is in the state of improvement and stability, and a small part is in the state of degradation. The main reason for the degradation is grassland degradation, and urban expansion leads to the degradation of cultivated land and the conversion of cultivated land to construction land. (4) NDVI is positively correlated with soil moisture at different depths (0−10 cm, 10−40 cm, 40−100 cm, 100−200 cm), with the correlation coefficients of 0.535, 0.647, 0.681 and 0.619, respectively. The correlation between NDVI of different land use types and soil moisture of different depths is different. The positive correlation area between NDVI and soil moisture of cultivated land, grassland and unused land is the largest at the depth of 10−40 cm, while the positive correlation area between NDVI and soil moisture of forest land is the largest at the depth of 40−100 cm.
Vegetation restoration and dynamic evolution analysis of landslide activity in the Wenchuan Earthquake area
LI Mingwei, XIONG Jiang, CHEN Ming, TANG Chuan
2023, 50(3): 182-192.   doi: 10.16030/j.cnki.issn.1000-3665.202209049
Abstract(183) HTML(169) PDF (12217KB)(26)
A great mountain seismic often triggers a large number of co-seismic landslides, causing direct damage to local vegetation cover and growth. As an important indicator of landslide activity intensity, the vegetation recovery is of great significance for the activity of post-earthquake geo-hazards. However, due to the limitation of observational data, the current research on vegetation restoration process in earthquake areas is mostly on a small scale. In addition, there is insufficient understanding of the vegetation evolution mechanism in a large area and the relationship between vegetation and the activity of geological disasters. Therefore, this paper uses multi-temporal and long-time series (2000−2020) high-precision remote sensing images to study the vegetation restoration process in the Wenchuan earthquake area. By calculating vegetation recovery rates in different periods, we explore the universal law of vegetation restoration in a large range, and analyze the relationship between vegetation restoration and the change of landslide activity intensity. The results show that by 2020, 71.34% of the landslide area in the earthquake area has been better restored. The proportions of highly active, moderately active, low active and basically stable landslides are 17.6%, 12.4%, 17.7% and 52.3%, respectively. The surface recovery trend of co-seismic landslide indicates that the vegetation in the Wenchuan earthquake area is expected to recover to the pre-earthquake average level about 17 years after the earthquake. However, the process of vegetation recovery and changes in landslide activity are often subject to the combined effects of multiple factors. Although the vegetation recovery of landslide surface reflects the decline of landslide activity after the earthquake to some extent, the effects of the earthquake on landslide activity will last longer than the recovery of surface vegetation to the pre-earthquake level. Referring to the results of previous studies, this paper suggests that the post-earthquake landslide activity will last 25 years or more.The conclusion can provide reference for the assessment and prevention of post earthquake geological disasters in Wenchuan earthquake area.
A preliminary study of the geothermal geological characteristics and exploration potential of the Sichuan Basin
SUN Dong, LI Jinxi, CAO Nan, LI Zhiwu, ZHANG Zhipeng, XIE Xiaoguo, YUAN Mengyu, CAI Hongyan
2023, 50(3): 193-206.   doi: 10.16030/j.cnki.issn.1000-3665.202110028
Abstract(1313) HTML(2994) PDF (4995KB)(78)
The Sichuan Basin located in the intersection of the Tethys−Himalaya and Pacific domains is a multicycle sedimentary basin surrounded by orogenic belts. The geothermal resources are good, but with complex geological structures. Geothermal conditions and heat generation models are different in different tectonic zones in the basin, which seriously restrict the geothermal exploration, development and utilization of geothermal resources. In this paper, the distribution of geothermal resources, characteristics of geothermal fluids, heat flow and geothermal gradients in the Sichuan Basin are comprehensively analyzed by collecting the existing geothermal and petroleum exploration and development data. The geothermal reservoirs and caprocks, the burial depth and the resource conditions of different types of the basin-mountain structure areas in the Sichuan Basin are analyzed. The suggested exploration target for exploration and development are proposed in different tectonic units of the Sichuan Basin. The results show (1) the terrestrial heat flow values in the Sichuan Basin and its surrounding areas are from medium to low, and the geothermal gradient varies between 16 °C/km and 30 °C/km. The terrestrial heat source is obviously controlled by active faults and basement structure, and the hydrothermal systems are conductive and belong to the low-moderate temperature geothermal resources in the Sichuan Basin. (2) The distribution of geothermal resources in the Sichuan Basin is mainly controlled by basin structure, stratigraphic distribution and hydrologic conditions. (4) There are at least 4 karst-type geothermal reservoirs in the marine strata, and 1 − 2 glutenite-type geothermal reservoirs in clastic strata. Geothermal water is of SO4 Ca type and is brackish. The Middle-Lower Triassic and Middle Permian carbonate rocks are considered as the best marine reservoirs, especially in the eastern and western basin. Secondly, other marine karst-type geothermal reservoirs are selected for exploration. The continental clastic rocks should be cautious because their caprocks, groundwater recharge and heat source are worse than the geothermal conditions of the marine carbonate rocks. This study may provide important guidance for further promoting geothermal exploration, exploitation and utilization in the Sichuan Basin.
Geothermal genesis and resource potential of Kaga in Xietongmen County in Tibet
ZOU Jun, WU Bin, MA Zhaoxiong, CHEN Ning, XIE Wei, ZOU Huamin, YANG Daibin
2023, 50(3): 207-216.   doi: 10.16030/j.cnki.issn.1000-3665.202208003
Abstract(218) HTML(170) PDF (9867KB)(29)
Xietongmen County is located in the alpine mountain area of the Qinghai-Tibet Plateau, where the Kaga hot spring occurs. Geothermal energy is expected to be developed to solve the local heating problem, but research on the genesis and reserves of geothermal energy has not been carried out. By analyzing the geological structure and geothermal activity law of the survey area, and carrying out detailed geological survey, audio frequency magnetotelluric sounding and soil radon measurement near the Kaga hot spring, this paper discusses the genesis and thermal reservoir characteristics of ths Kaga hot spring by comprehensively using geological and geophysical exploration data. The research results show that (1) the audio frequency magnetotelluric and soil radon measurement results clearly reveal the extension and superposition relationship of the deep NE, NW and SN trending faults in the area, indicating that the area has a good permeable channel and thermal storage space. (2) The heat source in the study area is composed of the middle and shallow Eocene Oligocene magmatic rock decay exothermic heat source and the deep high-temperature magmatic melting heat source. The fracture zone is not only a deep thermal reservoir, but also a channel for the upwelling of deep hot water. The alluvial proluvial and other accumulative layers in the upper part of the Quaternary system are good caprocks of geothermal water, while the unconsolidated sediments in the lower part of the Quaternary system and some bedrock weathering crusts constitute shallow geothermal reservoirs in the area. These indicate that the geothermal application potential in this area is large, but it should be noted that, according to the three-dimensional display of audio frequency magnetotelluric sounding results, it is found that the deep S1 and S2 abnormal areas are connected at the shallow part, and the surface hot spring vent is just above its connecting channel, so the impact of the water volume of this hot spring vent needs to be evaluated when drilling water nearby. Finally, combined with the geothermal characteristics and electrical characteristics of geothermal water in this area, the “geophysical geothermal geology” model of the survey area is constructed, providing reference and guidance for the exploration and development of geothermal resources in other regions of Tibet.

Supervisor: China Geological Survey

Sponsor: China Institute of Geo-Environment Monitoring

Chief Editor: Li WenPeng

Editor&Publication: Editorial Office of Hydrogeology & Engineering Geology

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