THREE-DIMENSIONAL SEEPAGE NUMERICAL SIMULATION OF DEEP FOUNDATION PIT DEWATERING IN COMPLICATED QUATERNARY LOOSE SEDIMENTS WITH GREAT THICKNESS—A CASE STUDY OF DEWATERING RECONSTRUCTED FOUNDATION PIT AT DONGJIADU SUBWAY OF THE 4TH LINE IN SHANGHAI
Abstract：The Quaternary loose sediment with great thickness and complex character in the Yangtze River delta is found，and the water table of the confined aquifer is so high that it is difficult to predict dewatering of deep foundation pit. A three-dimensional seepage model was established and three-dimensional finite difference numerical simulation method was adopted in foundation pit dewatering at Dongjiadu subway of the 4th line in Shanghai. The complicated flow state of groundwater was simulated under these conditions as follows：(1) the aquifers deposited layer by layer；(2) the bottom of the aquifers with thickness 150 m；(3) the horizontal flow barrier with thickness 65 m；(4) the pumping wells being penetrated to depth of 59 m；(5) the filters of the pumping wells being located between 44 m and 59 m；(6) thirty pumping wells being operated at the same time；and (7) the water level of the middle part of confined aquifer II under the center of foundation pit decreases to 43.35 m under ground surface. The result was proven to be correct and reliable by succedent project. It is concluded that it is very reliable to use the theories to simulate and predict the state change of groundwater flow in deep foundation pit dewatering in such areas.
