基于广义Mises条件的地基塑性区的确定

A Method to Determine Plastic Zone Under Strip Foundation Based on Generalized Mises Yield Criterion

在假设土的侧压力系数随倾角线性变化的情况下 ,利用广义 Mises条件和理想弹塑性理论导出了均质地基在条形荷载作用下塑性区发展的控制方程组 ,编制了求解程序。算例结果表明 ,由该法得出的塑性区与由 Mohr-Coulomb极限平衡理论法得出的塑性区差别较大 ,塑性区在较小荷载作用下就已经出现 ;且在荷载增加时主要向下发展 ,两侧塑性区连为一体的趋势不明显。分析原因主要是由于所用的广义 Mises屈服条件内切于 Mohr- Coulomb准则的缘故。考虑了中间主应力的作用和侧压力系数沿倾角的变化 。

Formulas were established and programmed to determine plastic zone induced by band-uniformly-distributed-load for homogeneous foundation based on linear relationship between lateral force coefficient and inclination angle, generalized Mises yield criterion and ideal plastoelastic theory. The calculation results showed that there were clear differences between the two kinds of plastic zones, which are defined respectively by the proposed method and by the referenced one. From the first one, plastic zone will appear when uploading is not very big and has tendency of extending downward directly and quickly and not joining together with each other. The reason for this phenomenon is that the circle of generalized Mises yield criterion is inscribed the one of Mohr-Coulomb. The proposed method is reasonable and practical because both the intermediate principle stress and change of lateral force coefficient with inclination angle were taken into account.