中文摘要：

模拟基坑开挖下的卸荷路径,进行了不同卸荷条件下包括围压、卸荷路径和排水的卸荷流变试验。试验结果表明：软土在竖向卸荷试验中的回弹变形可分为瞬时回弹变形和滞后回弹变形;在应力控制式三轴试验中,围压和轴压同时卸荷时的初始变形速率较大;仅卸轴压时回弹滞后效应明显,而围压、轴压同时卸荷时由于土体产生剪切变形引起负孔压,使土体回弹滞后效应不明显;在相同卸荷路径下,排水剪切时由于土体吸水膨胀使得流变特性更明显些,且产生的负孔压最终会消散。根据试验成果,建立Merchant流变模型参数与卸荷条件的线性函数关系,并将函数关系代入Merchant模型,最终得到能考虑围压及卸荷路径影响的软土卸荷流变经验模型。研究结果为软土流变变形模型研究及卸荷后基坑变形研究提供了参考。

英文摘要：

As the engineering practice indicated that the rheological behavior is obviously under unloading of the soft clay. According to the typical pit unloading paths, a series of unloading rheological tests were done with stress-control triaxial devices under different unloading conditions. The unloading conditions include confining stress, unloading stress paths and drainage conditions. Through experiments, the unloading rheological deformation of soft clay can be divided into instantaneous rebound deformation and bysteretic rebound deformation. When confining pressure and axial pressure unloaded under the same time, the initial strain rate is relatively larger on a short time after unloading; at the same condition, the hysteretic rebound effect is not obvious because the soil have negative pore pressure. When the axial pressure unloaded, the hysteretic rebound effect is more obvious. At the same unloading path, the rheological properties are more obvious under drainage condition because of that the soil makes water swelling, and the negative pore pressure will eventually be dissipated. Based on the test results, the linear function between the Merchant rheological model parameters and unloading conditions is established; and then established the soft soil unloading rheological empirical model which can consider the effects of the confining pressure and the unloading path. These conclusions are very useful to research the soft clay rheological deformation model and the calculation of excavation unloading rheological deformation.