Numerical Simulation of Stress Field Induced Groundwater Level Change in Confined Aquifer

XIE Yuqing, ZHAO Yonghong†

ACTA Scientiarum Naturalium Universitatis Pekinensis - - Contents - XIE Yuqing, ZHAO Yonghong

School of Earth and Space Sciences, Peking University, Beijing 100871; † Corresponding author, E-mail: zhaoyh@pku.edu.cn

Abstract The aquifer can be treated as poroelastic media in current research. An ideal 2D confined aquifer model was founded to calculate the response of the groundwater level to the variation of stress field. Then the dissipation law of abnormity of groundwater level was discussed. A deconvolution method to invert stress-strain field from groundwater level data when considering the dissipation process was also discussed. Results from forward calculation and earth tide data of Huili Chuan-06 well were analyzed to confirm the deconvolution method. At last, the mechanism of co-seismic step variation in groundwater level was analyzed. It was concluded that a simple poroelastic model cannot explain the amplitude of variation. Key words groundwater level; permeation; variation of stress field

井水位反映井水所在含水层对应位置和深度的静水压强, 并受井所在地区气压的影响。这个关系可以用下式表示:

P Hw H  , (1) a g其中, Hw表示水井水头(m), H表示承压含水层内井所在位置的压力水头(m), Pa表示大气压强(Pa), ρ 表示流体密度, g表示重力加速度。由于地下流体具有传递压力的能力, 因此有从地下深处(目前最深的井深度可以超过 3000 m)携带岩体的物理状态和介质的连通性等信息的可能性。

当地震孕育和发生时, 地下流体会产生异常现象,并且也参与地震孕育过程[1]。

1井水位变化与应力场关系1.1物理模型

车用太等[2]把震前地下水位动态异常信息分为4 个环节: 1)地壳应力活动与含水层应力状态的变‒含水层系统中的传递;化; 2) 含水层变形破坏与孔隙压力的变化; 3) 孔隙压变化信息在井 4) 孔隙压力变化信息在井孔地下水动态中的表现。他们认为异常信号的传递至少有 3 个途径, 首先分为固体介质传递和液体介质传递两大类, 液体介质传递又分

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