ISSN 1000-3665 CN 11-2202/P

    基于直推式点状注水试验推估松散含水层渗透系数的垂向变化

    Estimating vertical variations of hydraulic conductivity of an unconsolidated aquifer based on the direct-push point-source injection tests

    • 摘要: 渗透系数及其空间变化是影响地下水流和溶质运移过程的关键要素。传统的场地抽水试验或微水试验受“井—滤管”布设的限制,通常把含水层简化为均质模型,难以精准刻画渗透系数复杂的空间变化特征。近年来发展的直推式点状注水试验方法,依托直接推进的免成井技术,通过探杆侧壁的微型开口实现快速、高分辨率的点状注水。目前,对该试验数据的解释普遍依赖经验模型,其估算结果的精度与可靠性缺乏系统性评估。文章选取典型松散含水层加拿大的North Campus Research Site(NCRS)试验场,对比评估了场地拟合模型与传统经验模型在渗透系数定量推算方面的差异,探讨了点状注水试验与土样渗透试验以及微水试验这三种方法在不同渗透性介质层位中的估算效果,通过水流数值模型定量评价了不同方法的渗透系数估计值对注水水位动态模拟的影响。研究表明:直推式点状注水试验的高分辨率响应数据能够有效指示含水层介质垂向的渗透性变化,传统的经验模型会导致渗透系数出现明显高估或低估情况,而场地拟合模型可有效提高推估结果的准确性;相较于土样渗透试验和微水试验,点状注水试验能够更高分辨率地提供渗透系数估计值,但在低渗透性层位中,其渗透系数估计值对注水水位的模拟仍存在一定偏差。总体而言,直推式点状注水试验具备提供高分辨率渗透系数信息的潜力,能够为松散非均质含水层调查及三维高精度模型构建提供关键的水文地质参数支撑。

       

      Abstract: Hydraulic conductivity (K) and its spatial variability are critical factors governing groundwater flow and solute transport processes. Traditional methods, such as pumping tests or slug tests, often treat the aquifers as homogeneous to derive equivalent K values, making it difficult to accurately characterize the aquifer medium's intrinsic spatial heterogeneity. The emerging direct-push point-source injection test method, relying on casing-free direct advancement technology, enables rapid and high-resolution point-source injection through one miniature screen on the side of the probe. Currently, the interpretation of data from this type of tests predominantly relies on one empirical model, and the accuracy and reliability of its estimates lack systematic evaluation. Therefore, this study selected the North Campus Research Site (NCRS), a typical unconsolidated aquifer, to comparatively evaluate the differences between the site-specific model and the traditional empirical model in quantitatively estimating hydraulic conductivity. We analyzed and discussed the estimation effectiveness of the point-source injection test, soil permeameter tests, and slug tests across layers with different hydraulic conductivities. Furthermore, a numerical model was used to quantitatively analyze the impact of hydraulic conductivity estimates from different methods on simulated injection water level dynamics. This study indicates that the high-resolution response data from the direct-push point-source injection tests can qualitatively indicate vertical variations in aquifer media permeability. The traditional empirical model can lead to significant overestimation or underestimation of hydraulic conductivity, whereas the site-specific model can effectively improve estimation accuracy. Compared to permeameter tests and slug tests, the point-source injection test can provide hydraulic conductivity estimates more conveniently and efficiently. However, for low-permeability layers, its estimates still lead to deviations in simulating injection water levels. Overall, the direct-push point-source injection tests have great potential to provide high-resolution hydraulic conductivity information, offering crucial hydrogeological parameter support for investigating heterogeneous unconsolidated aquifers and constructing high-precision three-dimensional models.

       

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