土体小应变剪切模量的现场和室内试验对比及工程应用

土体小应变剪切模量G_0在场地地震响应和基坑变形等计算分析中有着重要作用。统计了上海典型土层的室内共振柱试验和现场原位波速测试测得的小应变剪切模量,给出了两种试验方法下的G_0的经验公式,并对比分析了室内试验和现场原位测试结果的差异。研究结果表明土体的G_0值主要由土体类别、孔隙比和平均有效应力决定,且现场试验的结果远高于室内试验的结果。进一步采用HS-Small本构模型对上海新金桥广场基坑工程的开挖变形进行数值模拟,分析了小应变剪切模量对于基坑工程变形的影响。分析结果表明,采用现场原位测试测得的小应变剪切模量进行基坑变形计算的结果与现场变形监测数据更为接近。

Comparison and application of small strain shear moduli from field and laboratory measurements

The small-strain shear modulus plays an important role in the calculations of ground seismic response and deformation in deep excavations. The values of the small strain shear modulus G₀ of Shanghai soils by field and laboratory tests are investigated and compared, and empirical formulas are proposed to predict the values of G₀. The results indicate that G₀ mainly depends on the soil type, void ratio and mean confining pressure. The values of G₀ from field tests are considerately higher than those from laboratory tests. The correlation between the small strain shear moduli from field and laboratory is also proposed. The numerical analysis is also carried out to calculate the deformation in a deep excavation in Shanghai. The small strain hardening model (HSS) is used, together with the measured small strain shear modulus. The values of G₀ are essential for the deformation of the excavation, and the predicted deformation using the G₀ value from field measurement is more accurate than that using the laboratory data based on the measured deformation in the excavation.