| More and more buildings are constructed in the downtown area, and deep construction pits have to be dug at the initial stage of construction. For the convenience of excavation, groundwater pumping is carried out before digging, and the watertable lowering leads to adjacent ground and existing buildings settlement. Plenty of practical cases show the catastrophic effects of groundwater pumping. So, it is significant to find a way to predict the scope of settlement area and the magnitude of maximum settlement. Usually, the settlements of adjacent ground and building are caused by both groundwater lowering and the deformation of pit wall. However, in Zhengzhou, a Central China metropolis, on the Yellow River, enough practical surveys show that the pit wall deformation is no more than dozens of millimeter, and is not able to propagate far away. So, in this paper, it is taken for granted that the adjacent ground and building settlement are caused by the groundwater pumping, i.e., the pit wall deformation is neglected in the following discuss.Based on 2-D steady flow theory, the space character of conic surface of lowed water caused by construction pit dewatering is deduced, then derived from Effective Stress Principle (ESP), the ground settlement calculation model is suggested. Then, it is simplified in the form of Laminated-Settlement-Accumulation model, which is recommended in the current National Code. The analysis reveals that the ground settlement is in direct proportion to the two-time-power of value of watertable lowing. In the three practical cases, the lowing of watertable, calculated ground settlement and practical surveyed settlement are compared. It is supposed that the scope of ground settlement is rather smaller than the water lowering influence area, and their relationship is obscured by the variation of compression modulus of site soil. At the same time, the heaped load and traffic load in the adjacent area of construction pit play important role in the ground settlement. |
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