一种旋转塑性势面模型及非关联塑性流动法则

A rotational plastic potential model and non-associated plastic flow rule

为了较好地描述软土塑性应变发展规律,提出了一种改进的塑性流动模型。该模型采用了与屈服函数形式相同,但具有一定倾角γ的塑性势函数。土体在变形过程中,塑性流动方向会依赖于塑性势面的旋转而变化,直至达到破坏状态。通过对常规三轴试验结果的分析可以发现:在剪切过程中,塑性势面旋转角的初值γ0与终值γd较为稳定,不受围压变化影响。在此试验观察基础上,引入了归一化的旋转角参数γ’以及描述土体应力状态的参数ξ,在采用蛋形势函数的情况下二者具有良好的分段线性关系。利用该关系,建立了改进的塑性流动法则,只需要2个额外的模型参数。对所提出的塑性流动模型进行了验证,计算结果表明该模型能较好地反映塑性应变的变化趋势。

In order to accurately describe the evolution of plastic strain for soft soil,an improved plastic potential theory is proposed,in which a plastic potential surface with an inclination angle γ is employed.In addition,the plastic potential function shares the same form as the yield function.During deformation,the plastic flow direction varies following the rotation of the plastic potential surface until the limit state is reached.By analyzing the results of conventional triaxial tests,it can be found that during the shearing process,the initial and final values of the rotation angle of the plastic potential surface γ0 and γd,are basically stable and independent on the confining pressure.Considering such observations,a normalized rotation angle γ’ and a state parametere describing the stress state of the soil are introduced,in the case that the egg-shaped function is used as plastic potential function.A piecewise linear relationship can be obtained.Then an improved plastic flow rule is established,only two additional parameters are required.Finally,the proposed plastic flow model is verified,and the results show that the trend of plastic strain can be reflected well in this model.