循环复合加载条件下裙板式基础下的地基承载力

BEARING CAPACITY OF SKIRTED FOUNDATIONS SUBJECTED TO CYCLIC COMBINED LOADING

为了合理考虑软黏土发生强度弱化的循环软化效应,将软黏土循环强度概念与不排水条件下邓肯-张非线性弹性关系与Mises屈服准则相结合,提出非线性弹塑性-循环强度模型。进而对于循环复合加载条件下裙板式基础的稳定性以及动静耦合现象进行有限元模拟,并与已有的模型试验及计算结果进行比较。结果表明:裙板式基础下地基所承受的峰值动荷载相对于其极限承载力有较大降低,不考虑土体屈服前非线性弹性所得到的峰值动荷载偏高。当基础所受的静荷载较小时,地基破坏主要由循环荷载引起,而当基础所受的静荷载较大时,地基破坏主要由静荷载引起。

To consider reasonably the cyclic softening effect with strength degradation of soft clay , a nonlinear elasto-plastic model based on the concept of cyclic shear strength of clay was proposed .In the model, the concept of cyclic strength was combined with the Duncan-Chang nonlinear elastic relationship and Mises yield criterion under undrained condition .Then a series of finite element analysis were conducted to explore the stability and cyclic and static coupling effect of skirted foundations in soft ground .The results computed were verified through comparing with the available model test under monotonic loading . The results indicated that the peak cyclic load was reduced considerably with respect to ultimate bearing capacity .Parametric studies showed that the peak cyclic load without considering the nonlinear elastic relationship was higher than that reflecting the effect .When the static vertical load level was smaller , the instability of foundation was caused mainly by cyclic load , whereas the level was larger , the failure of foundations was due to static load .