Consolidation Analysis of Aquitard Induced by Dropping of Groundwater Table with Continuous Drainage Boundary
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摘要:
为探究更能反映实际透水能力的排水边界对超采地下水导致的地面沉降问题的影响,首先,通过引入孔压随时间指数衰减的连续排水边界,建立连续排水边界下潜水层水位变化引发的下卧弱透水层一维固结模型;其次,采用分离变量法获得其模型普遍解析解答以及水位瞬时下降和水位单极等速下降2种特殊降水模式的解析解;然后,通过特定条件下解析解的退化初步验证本文解析理论的正确性;最后,以水位单级等速下降为例,利用本文解计算不同界面参数下弱透水层的固结曲线,着重分析界面参数对固结性状的影响. 结果表明:理论计算的沉降曲线与室内试验沉降曲线对比,最大误差为13%,进一步说明连续排水边界更贴合实际透水边界;界面参数越大(排水边界透水性越好),孔压消散速率越快,固结速率越快,越早完成固结,但其并不影响最终固结状态.
Abstract:In order to investigate the influence of the drainage boundary, which can better reflect the actual permeability, on the land subsidence caused by over-exploitation of groundwater, firstly, a one-dimensional consolidation model of aquitard caused by the dropping of groundwater table in phreatic aquifer with continuous drainage boundary was established by introducing the continuous drainage boundary, where the pore pressure decayed exponentially with time. Secondly, the general analytical solutions of the model and the analytical solutions of two special precipitation models for the instantaneous dropping of the groundwater table and the single-stage and constant-rate dropping of the groundwater table were obtained by using the method of separate variables. Then, the correctness of the analytical theory in this paper was preliminarily verified by the degeneracy of the analytical solutions under certain conditions. Finally, the single-stage and constant-rate dropping of the groundwater table was taken as an example, and the consolidation curves of the aquitard under different interface parameters
B were calculated based on the analytical solutions. In addition, the influence of interface parameterB on the consolidation behaviors was analyzed emphatically. The results show that the maximum error rate is 13% by comparing the theoretically calculated settlement curve with the experimental settlement curve, which further indicates that the continuous drainage boundary is closer to the actual permeable boundary. Furthermore, larger interface parameterB indicates (better water permeability of the drainage boundary) a faster pore pressure dissipation rate, faster consolidation rate, and earlier consolidation, but the final consolidation state is not affected. -
表 1 固结性状分析采用的模型参数
Table 1. Model parameters adopted in consolidation behavior analysis
参数 数值 γsat/(kN·m−3) 20 γ/(kN·m−3) 18 γw/(kN·m−3) 10 H/m 10 mv/MPa−1 0.1 Tvc 0.1 hc/m 5 -
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