考虑桩体损伤的柔性基础下刚性桩复合地基中桩体受力及破坏特征分析

Analysis of stress and failure mechanism on composite foundation improved by rigid piles under flexible foundation considering damage of piles

为了模拟桩体局部损伤或破坏后的应力迁移,采用混凝土损伤模型实体单元,利用ABAQUS软件建立柔性基础下刚性桩复合地基三维分析模型,研究路堤填筑及后期加载过程中刚性桩复合地基中桩体的受力状态及破坏特征。研究结果表明:损伤模型能较好的模拟混凝土桩体受损后桩身刚度降低、内力重分布的过程;而线弹性桩体模型所得桩身弯矩偏大,桩身位移偏小;桩体所能承受的极限弯矩与其在复合地基中的位置有关,且与纯弯状态下的桩体极限弯矩有较大差异;路肩以外桩体破坏模式主要表现为拉弯和压弯破坏;路堤中心下方的桩体以承受竖向压力为主,桩体先破坏的可能性不大,其破坏往往是由于路堤边坡失稳后诱发产生的;复合地基中刚性桩发生受剪破坏的可能性不大。

To simulate the stress migration in local damage and cracking of piles, ABAQUS software was used to establish a 3-D analytical model of composite foundation improved by rigid piles with concrete damage plasticity model. Stress and failure mechanism of piles were studied in the process of embankment reclamation and loading. The results show that concrete damage model has good performances in predicting the reduction of pill stiffness and redistribution of internal forces; the linear elastic model yielded higher moment and lower displacement; Unlike ultimate moment under pure bending, the maximum moment in pile depends on its location with respect to the embankment; When the embankment is approaching failure, piles outside the shoulder tend to subject to stretch-bending or compression-bending failure while piles close to the embankment center mainly bear vertical pressure; pile failure could hardly occur in the first place as it is usually caused by failure of embankment slope; Shear failure unlikely occur in rigid piles.