| Aiming at solving the problem of land subsidence caused by well-pumping in deep pit at the region of Shanghai,the paper is based on the project of Yi Shan Road station of Shanghai Rail Transit Line 9.Combining with outdoor well-pumping tests and indoor well-pumping comparison model tests,there are some useful conclusions and outcome:1. When precipitating in Fine Sand Layer which is confined,it has completed most of the settlement after flow feild steady.It will take a longer time for reaching stable settlement because of water-losing effect in clay layers.2. Elastic water yield in Main confined aquifer and water-losing effect in clay layers are the dominant factors leading to the settlement.3. After the cessation of precipitation the layers and the soil surface rebound quickly.They reached basically stable within 3 days because the rebound belongs to elastic deformation.Resumption of land subsidence is generally in the smaller limits,Conjecturing within 10mm.4. The behavior of land subsidence was obviously affected by layered settlement. The key to reduce layered settlement is controlling the settlement of main confined aquifer and the clay layers on it.5. Currently quantity of the soil surface reinforcement methods is far more than that of the ones of controlling Deep Soil subsidence.And deepening diaphragm wall has been proved effectively in my paper.Expansive soil reinforcing moisture layer is a good way controlling layered settlement also.6.The key to controll water lever in confined aquifer and land subsidence is the depth of inserting Fine Sand Layer. It's obvious whether the pit diaphragm wall inserts Fine Sand Layer effectively or not.Depth of the diaphragm wall of Rail Transit Line 9 increased 10m(modifying 52m to 62m). This not only has minished the value of land subsidence outside the pit,but also has shortened the scope of it.7. The diaphragm wall inserting Fine Sand Layer effectively extends hydraulic...
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