强夯地基垫层厚度对承载力与变形模量的影响

Analysis of impact of dynamic compaction foundation cushion thickness on bearing capacity and deformation modulus

对江苏省连云港赣榆港区吹填土强夯地基进行了两组现场载荷试验,探讨不同强夯垫层厚度的强夯地基承载力特性。在现场试验基础上,采用有限元法分析垫层厚度对附加应力系数和传递深度的影响,结果表明强夯垫层能有效增大附加应力的扩散作用,明显提高地基承载力,附加应力在2倍板径深度范围内下降到板底应力的6%以下;但地基土屈服后会使附加应力往深层传递。综合数值模拟的结果分析,表明附加应力与自重应力比值为0.2时所确定的计算深度随板底应力水平的增大而增大,不是一个固定值。在此基础上探讨了载荷试验反演的地基变形模量与按垫层厚度的加权模量间的关系,结果表明按厚度加权获得的地基平均模量为载荷试验反演的变形模量的1.2倍。

In this study,two groups of field loading tests are performed to study the influences of the cushion on the bearing capacity after the dynamic consolidation at Ganyu port in Lianyungang city. According to experimental data from two groups tests,the cushion thickness effects on the additional stress coefficient,influence depth of loading plate and average deformation modulus have been analyzed by using FEM numerical simulation. The analysis results show that the thickness of the cushion significantly reduces settlement and improves additional stress diffusion. And the additional stress coefficients would drop to below 6% of the stress at bottom of the plate at the 2 times of the plate diameter; when the foundation comes into yielding,the coefficients would be intensified. The influence depth of the plane load test would increase with the increase of the stress level at the plate bottom,not a constant ratio to the diameter of the plate. In addition,the relationships between the average deformation modulus weighted by the cushion thickness and that back-analyzed by the PLT tests are also discussed in this paper,and the results indicate that the the average deformation modulus weighted by the cushion thickness is 1. 2 times higher than that of the latter,which can be used to estimate the reasonable foundation modulus.