A study of the critical groundwater level related to soil consolidation characteristics of land subsidence in Cangzhou

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 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, 67.5 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 the urban of 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.