基坑降水对土侧压力系数的影响

针对上海软土深基坑开挖降水过程中所涉及的③层淤泥质粉质粘土、④层淤泥质粘土、⑤-1层粉质粘土、⑤-2层粘质粉土，通过二阶段固结模拟和K0试验，研究了各层土在不同降水深度条件下土侧压力系数K0的变化特性。试验结果显示：（1）降水前后，粘性土K0值相对粉性土K0值为大。（2）各层土侧压力系数K0值均随水位降深的增加而减小，单位水位降深，⑤-1层、⑤-2层、③层、④层土的侧压力系数K0值分别下降3.1%、2.5%、2.3%、1.3%左右。（3）随着降水深度的增大，降水对侧压力系数的影响在逐渐减小，并最终趋于稳定。最后，基于回归分析理论得到侧压力系数简化计算公式，为上海地区深基坑降水土侧压力系数的确定提供依据。

Experimental Study on Influence of Foundation Pit Dewatering on Lateral Pressure Coefficient of Soil

Aiming at the layer 3 mucky silty clay,the layer 4 mucky clay,the layer 5-1 silty clay and the layer 5-2 clayey silt involved in the process of excavation and dewatering of deep foundation fit in soft soil stratum of Shanghai,a study was made on the variation characteristics of the lateral pressure coefficient for the soil layers in different drawdown through the two step consolidation method and K0 test.The test results show that the lateral pressure coefficient value of the clay is larger than that of the silt before and after dewatering.The lateral pressure coefficient of the soil decreases with the increasing of the drawdown,and the lateral pressure efficient value of the layer 5-1,the layer 5-2,the layer 3 and the layer 4 decreases about 3.1%,2.5%,2.3% and 1.3% per meter drawdown respectively.As the drawdown increases,the influence of dewatering on the lateral pressure coefficient is decreasing gradually,and finally the lateral pressure coefficient tends to be stable.In the end,the simple calculation formulas of the lateral pressure coefficient were obtained based on the theory of regression analysis,providing reference for the determination on the lateral pressure coefficient of the soil after dewatering of the deep foundation pit in Shanghai.