承压水降压引起的地面沉降由含水层、弱透水层和潜水层的变形组成。当承压层降压时间短、弱透水层固结变形较小时，可以假设弱透水层为严格的隔水层。采用层状弹性体系理论，基于位移协调条件分别建立了单井抽水以及第三类基坑工程降水（隔水帷幕插入降水含水层）引起的土层变形分析模型，与数值模拟和现场抽水试验结果的对比，验证了文中方法的正确性。研究结果表明，上覆土层弹性参数变化对地表变形的影响可以忽略；抽水井附近的土层变形呈现“上小下大”特点，一定距离以外含水层与地面沉降大致相等，根据承压含水层降深要求，可估算出基坑外的水位降深。

Land subsidence caused by decompression of confined water is comprised of deformations of aquifer, aquitard and phreatic stratum. When the decompression features short duration so that consolidation deformation of aquitard is little, the aquitard is supposed to be watertight. Theory for elastic layered system is adopted to calculate layered soil deformation caused by dewatering of single well and the third type of foundation pit dewatering that the waterproof curtain inserts into the confined aquifer. The calculated results are compared with numerical simulation and in-suit tests results. The analytical results show that elastic modulus of the overlying soil has little influence on ground surface displacement; yet thickness of overlaying soil layer shall be taken into consideration. The settlement of soils overlying confined aquifer increases up to down nearby the pumping well. Over a certain distance, the settlement does not change with depth. The drawdown outside the foundation pit can be estimated according to the demand for drawdown inside the foundation pit.