浸水条件下膨胀性红层砂岩地基扩底桩抗拔承载特性

Uplift bearing capacity of enlarged base piles in expansive red sandstone under water immersion condition

红层砂岩在我国中西部地区分布广泛,浸水条件下其力学特性变化大,因而合理确定红层砂岩地基中抗拔桩承载力是工程设计关注的问题。通过引入温度场比拟湿度场的三维弹塑性有限元数值分析方法,开展了浸水条件下扩底抗拔桩基础承载特性模拟,研究了不同桩长扩底桩浸水前后承载力变化以及塑性区分布特征。模拟结果表明:浸水将导致红层砂岩扩底桩的抗拔极限承载力降低,浸水前后桩基抗拔极限承载力均随桩长增加而增加,但浸水后承载力随桩长的增加值有一定减小。抗拔极限状态下,桩周土体塑性区分布在空间上呈楔形体加四棱柱体的组合形式,浸水将导致塑性区缩小,但随着桩长增加,塑性区面积有一定扩大。

Red sandstone widely distributes in central and western China.The bearing characteristics of pile foundation for transmission line tower greatly varies when the red sandstone subjected to water immersion,the determination of the ultimate uplift bearing capacity of pile is a problem worthy of attention in engineering design.By comparing temperature field with humidity field,the three-dimensional elastoplastic numerical simulation method is proposed to study the uplift bearing capacity of enlarged-base pile under immersion condition.The results show that water immersion induces the ultimate bearing capacity decreases.The ultimate bearing capacity increases with pile length,and it increased value with pile length decreases after soil immersion.The failure mode of an uplift pile with enlarged base is composed of a wedge and a quadrangular.The failure zone will be reduced by water immersion,and the zone gradually expands with the increase of pile length.