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Abstract Land subsidence caused by groundwater overpumping is becoming a serious geological disaster. Based on previous studies，testing device of land subsidence was manufactured and the saturation method of sample was improved. Land subsidence caused by water releasing was simulated by the use of this device. Hysteresis effect of land subsidence was studied on land subsidence response to changes of water level and pore water pressure in the process of land subsidence. The results show that：(1) The deformations of both confined aquifer and clay layer show lag phenomenon；(2) Under the same test conditions，the lag-time of deformation of clay layer was (going longer with the thickness of caly layer)in direct proportion to thickness of clay layer. When the test was completed，clay specimens were taken out from the bottom and top of clay layer respectively and measured by conventional consolidation test. The results indicate that the land subsidence caused by water releasing was not uniform in the vertical direction. The shorter the distance between the clay layer and the pumping aquifer is，the greater the degree of compression of the clay layer is.
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Received: 10 September 2010
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2011, Vol. 30 
