Key Laboratory of Land Subsidence Monitoring and Prevention, Ministry of Land and Resources (Shanghai Institute of Geological Survey), 930 Lingshi Road, Shanghai, 200072, China.
School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Avenue, Nanjing, 210023, China.
Ground Water. 2020 Mar;58(2):278-290. doi: 10.1111/gwat.12909. Epub 2019 Jun 21.
Excessive groundwater withdrawal has caused severe land subsidence worldwide. The pore water pressure and the deformation of pumped hydrostratigraphic units are complex. A fully coupled three-dimensional numerical simulation was carried out for different pumping plans in this paper. When groundwater is pumped from a confined aquifer, the great compaction occurs in the pumped aquifer and its upper and lower adjacent aquitard units. Land subsidence is smaller and the area affected by land subsidence is greater when groundwater is pumped from the deeper confined aquifer. The pore water pressure in the pumped confined aquifer changes immediately with pumpage. In the adjacent aquitard units, however, the pore water pressure increases in the early pumping time and decreases in the early recharging time. The decrease in the pore water pressure vertically spreads from the interface between aquitard and pumped aquifer to the other surface of the aquitard. The pumped aquifer compacts and rebounds immediately with pumping and non-pumping or recharging actions, while the compaction and rebounding of the aquitard units clearly lag behind. The compaction of the adjacent aquitard unit first occurs near the interface between aquitard and pumped aquifer units, and the compaction zone spreads outward as the pumping goes on. The aquitards may expand vertically within some zones. Due to the inelastic deformation of soil skeleton, different pumping plans result in different land subsidence. For the same net pumpage, maximal land subsidence and horizontal displacement are the smallest for constant discharge and the greatest for recharge-discharge cycle.
地下水超采已在全球范围内造成严重的地面沉降。抽取含水层中的地下水时，孔隙水压力和抽采水文地质单元的变形非常复杂。本文针对不同的开采方案进行了三维全耦合数值模拟。当从承压含水层中抽取地下水时，被抽取的含水层及其上下相邻的隔水层单元会发生强烈的压缩。当从较深的承压含水层中抽取地下水时，地面沉降较小，受地面沉降影响的面积较大。承压含水层中的孔隙水压力随抽水量的变化而立即发生变化。然而，在相邻的隔水层单元中，孔隙水压力在早期抽水时会增加，在早期充水时会减少。孔隙水压力的减少会从隔水层与被抽采含水层的界面垂直向上传播到隔水层的另一侧表面。被抽采含水层会随着抽水、停抽或充水立即发生压缩和回弹，而隔水层单元的压缩和回弹明显滞后。相邻隔水层单元的压缩首先发生在隔水层与被抽采含水层单元的界面附近，随着抽水的进行，压缩区向外扩展。在某些区域，隔水层可能会发生垂直膨胀。由于土壤骨架的弹塑性变形，不同的开采方案会导致不同的地面沉降。对于相同的净抽水量，恒排量方案的最大地面沉降和水平位移最小，充-放循环方案的最大。
