一种基于土体率敏性的长期变形预测方法

土体长期变形的预测与控制是大量工程建设的关键性问题。常规方法是结合蠕变试验来预测土体变形,其存在耗时长、难以考虑复杂应力路径以及不便用于复杂有限元计算分析等缺点。考虑土体的率敏性特征,通过对饱和超固结土以及人工制备结构性土分别开展3种不同加载速率下的三轴剪切试验,获得了土体强度、变形以及率敏性指标,从而得到了基于上下负荷面的弹黏塑性本构模型参数,并利用该模型成功预测了土体的率敏性和蠕变变形行为。结果表明:①结合土体率敏性试验来预测土体长期变形,仅较常规土三轴试验增加了几组不同加载速率的剪切试验,而不需增加额外的试验条件,试验效率高;②由土体率敏性试验确定的本构模型参数能正确预测土体的蠕变变形,试验结果与模型预测结果吻合良好;③基于上下负荷面的弹黏塑性本构模型可用于复杂边值问题的有限元计算。结果表明提出的结合土体率敏性来预测土体长期变形的新方法将具有很好的工程应用价值。

A Method of Predicting Long-term Deformation of Clay Based on Rate Sensitivity

The prediction and control of the long-term deformation of clay is a crucial problem in the construction of a large quantity of projects. Predicting clay deformation conventionally via creep test is time-consuming, challenging in considering complex stress path, and also unsuitable for complicated finite element analysis. In this paper, the strength, deformation and rate sensitivity of saturated over-consolidated clay and artificial structural clay were obtained via triaxial shear tests under three different loading rates. On this basis, parameters of an elastic-viscoplastic constitutive model based on super-subloading surface were obtained, and the rate sensitivity and creep deformation of clay were estimated by the model. Results revealed that: 1) compared with conventional triaxial test, predicting the long-term deformation of clay in association with rate sensitivity test is highly efficient with only several shear test at different loading rates added yet no additional test conditions; 2) the parameters of the constitutive model determined by rate sensitivity test can be used to predict the creep deformation of clay correctly, and the prediction results are in good agreement with test results; 3) the elastic-viscoplastic constitutive model based on super-subloading surface can be embedded in finite element program to calculate the complex boundary value problems. In conclusion, the presented method of long-term deformation prediction of clay is of sound value in engineering application.