近年来上海及苏锡常地区的地面沉降出现了含水层砂土持续变形的新特征，现有的地面沉降理论无法完全解释与预测此现象。地下水长期开采会在含水层中形成水力漏斗，如果抽水井在一定范围内密集分布，就将在含水层中较长距离内形成水力梯度，从而产生无法忽视的剪应力，剪应力不断累积将导致含水层变形及地面沉降。含水层水位下降引起的土层中剪应力累积是造成含水层变形问题的重要原因，传统的Cauchy力学理论因为模拟单元较小，存在剪应力互等的假设而无法计算此部分剪应力；而Cosserat力学理论考虑了介质尺度的影响，可以计算连续体中的非对称剪应力分布，因而能够考虑由水位变化产生的剪应力引起的含水层变形。%The recent monitoring of land subsidence and soil deformation in the Shanghai and Suzhou-Wuxi-Changzhou regions indicated that aquifer sand can cause excessive deformation, which wil only occur at the yield condition. Current research cannot explain the factors that lead to the excessive deformation of aquifer sand under lower vertical stress. When groundwater is pumped from densely distributed wel s, a wide hydraulic funnel wil form. Then, a hydraulic gradient wil form in the aquifer that wil lead to shear stress in the aquifer sand. Accumulated shear stress wil result in the deformation of the aquifer, and especial y land subsidence. So, the accumulated shear stress due to the drawdown of the groundwater level is one of the important causes of aquifer deformation. Traditional Cauchy continuum mechanics cannot consider this shear stress due to the hypothesis of equal shear stress in the aquifer unit. Cosserat continuum mechanics can be used to analyze the deformation of aquifers due to the action of accumulated shear stress by considering the scale effect and the asymmetric distribution of shear stress in the aquifer unit.
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