上海地区不同强度参数对基坑围护结构变形和内力的影响

为研究上海地区不同强度参数对基坑围护结构变形和内力的影响,在ABAQUS中建立平面竖向弹性地基梁法模型,根据上海地区4种典型基坑概化模型和上海195个工程勘察报告和文献试验数据统计的典型土层强度参数,研究了每类基坑概化模型中不同强度参数对围护结构的最大水土压力、变形(最大位移)、内力(最大剪力、最大弯矩)以及支撑轴力的影响。结果表明:采用三轴固结不排水(CU)有效应力强度参数得到的围护结构变形和内力结果最小; 采用十字板不排水抗剪强度计算的结果相比有效应力强度参数结果无明显规律; 直剪固结快剪和CU总应力强度参数计算得到的结果较为接近,相比于有效应力强度参数结果,最大位移增量约为6%,最大水土压力增量为4%～5%,最大弯矩和剪力增量为7%～8%; 总体来看,目前上海基坑规范采用固结快剪总应力强度参数进行围护结构设计相比采用有效应力强度参数偏安全。

Influence of Different Strength Parameters on Deformation and Internal Force of Retaining Structures in Shanghai

In order to study the influence of different strength parameters on the deformation and internal force of retaining structures in Shanghai, the model of plane vertical elastic foundation beam method was established in ABAQUS. Based on four kinds of typical excavation generalized models and soil strength parameters collected from 195 engineering investigation reports and literature test data in Shanghai, the influence of four sets of different strength parameters on the maximum soil and water pressure, deformation(maximum displacement), internal force(maximum shear force, maximum bending moment)and strut axial force of retaining structure in each kind of generalized model were studied. The results show that the deformation and internal force of the retaining structure obtained by using triaxial consolidation undrained(CU)effective stress strength parameters are the smallest, while the results calculated by vane undrained shear strength have no obvious rule compared with the results of effective stress strength parameters. The calculated results of direct shear consolidation quick shear and CU total stress strength parameters are relatively close. Compared with the results of effective stress strength parameters, the maximum displacement increment is about 6%, the maximum soil and water pressure increment is 4%-5%, and the maximum bending moment and shear increment is 7%-8%. Generally, in the current Shanghai excavation code, it is safer to adopt the total stress strength parameters of direct shear consolidation quick shear test for the design of retaining structure than to adopt the effective stress strength parameters.