单向压缩状态下上海地区软土的蠕变变形与次固结特 性研究

基于上海地区原状软土的一维固结试验,讨论了在不同加荷比、加荷速率及超载预压情况下软土的蠕变变形特性和次固结特性。试验结果表明:蠕变变形随应力水平、加荷速率的增大而增大。相同应力水平下,加荷比较大的土样蠕变变形较小。蠕变变形为非线性,随着应力水平的增加,蠕变变形从粘弹性到粘塑性转变,加荷比较大时,这种转变更明显。对试验结果进行曲线拟和,确定Metchell一维经验模型参数,拟和曲线与试验结果吻合较好。通过对次固结阶段试验数据的线性拟合可知,对于正常固结土,次固结系数Ca值受应力水平和加荷比的影响不大,而与加荷速率密切相关,加荷速率较大时,Ca值随荷载的增大急剧增大后略有降低。超载预压可有效减小次固结系数,从而有利于减小工后次固结沉降。

ONE-DIMENSIONAL CONSOLIDATION TESTS OF CREEP DEFORMATION AND SECONDARY CONSOLIDATION CHARACTERISTICS OF SOFT SOILS IN SHANGHAI AREA

Based on a series of one-dimensional consolidation tests, the characteristics of creep deformation and secondary consolidation of Shanghai undisturbed soft soils were studied for different load ratios, different load velocity and overload pre-pressure. The test results showed that, creep deformation increased along with the increase of stress level and load velocity. For a constant stress level, the creep deformation decreased with the increase of load ratios. The creep deformation presented non-line characteristic and transferred from visco-elasticity to visco-plasticity while stress increased. When load ratios were high, the transformation was obviously. The parameter of Metchell one-dimensional model could be gotten by simulating experimental data and the curves tally with experimental data.It could be drawn from the analysis of testing data that for normally consolidated soils, the coefficient of secondary consolidation Ca wasn't affected by stress level and load ratios obviously, but it was related to load velocity closely. When the load velocity increased, Ca increased rapidly and then decreased slightly with stress rising. In addition, surcharge preloading can decrease the value of Ca and thereby is propitious for reducing the construction settlement.