软黏土卸荷变形特性室内试验研究与数值模拟

LABORATORY TEST AND NUMERICAL SIMULATION OF DEFORMATION CHARACTER FOR SOFT CLAY IN UNLOADING CONDITION

利用在常规三轴仪的基础上改制而成的应力控制式三轴仪进行了加(卸)荷作用下软黏土变形特性的室内试验研究,得到了以下的结论:(1)在加荷载和卸荷载大小相同的情况下,卸荷过程中的变形量比加载过程中的变形量小,约为加载过程中的变形量的十分之一;(2)当卸荷比例比较小时,试样的回弹变形量非常小;(3)当卸荷比例达到某一定值以后,试样的回弹变形量会显著地增加;(4)当卸荷比例超过另一定值以后,试样的回弹变形量将会趋于稳定。应用有限元分析软件ABAQUS对试验过程进行了数值模拟,得到了以下的结论:(1)在加荷载和卸荷载大小相同的情况下,软黏土加(卸)荷过程中的位移-时间关系曲线相似;(2)在分级卸荷的初始阶段和分级卸荷的最后阶段,用修正剑桥模型计算的变形增量要比试验得到的变形增量稍大,在中间阶段,用修正剑桥模型计算的变形增量与试验得到的变形增量可以较好地吻合;(3)在每一级的卸荷过程中,位移随时间的变化关系与试验结果吻合的很好。

The displacement-time relationship curves are got from laboratory tests for the deformation character analysis of the soft clay in unloading condition.The stress control triaxial compression apparatus is used and remade from the strain control compression apparatus.The following conclusions are gained from the analysis of the test results：（1）when the amount of the loading and the unloading are the same,the amount of the deformation produced in the unloading process is much smaller than the amount of the deformation produced in the loading process.The former is just about one tenth of the latter;（2）the resilience is very small,when the portion of the unloading is small;（3）the resilience will increase sharply,when the amount of the unloading is big enough;（4）the resilience deformation will trends to be stable,when the portion of the unloading exceeds another point. The finite element analysis software ABAQUS is used to simulate the laboratory test.The displacement-time relationship curves are got from the numerical simulation analysis.They revealed the following results：（1）the deformation-time curve in the unloading process is similar to the deformation-time curve in the loading process,when the amounts of the loading and unloading are the same;（2）the numerical calculated deformation increments are a little bigger than the deformation increments got from the indoor test in the initial and last periods of the whole unloading process,but fits well in the middle periods;（3）in every level of the unloading process,the relationships between the deformation and time got from the numerical simulation fit well with that got from the test.