方形平板锚抗拉承载力的大变形有限元分析

Large deformation finite element analyses of uplift capacity of square plate anchors

基于网格重分和改进的REP应力恢复技术,建立了三维大变形有限元方法研究拉力作用下方形平板锚与黏性土地基的相互作用。与常规的小变形有限元不同,大变形分析能够完整模拟平板锚的上拔过程,如果平板锚底面与土体始终保持接触,三维大变形计算得到的方板与圆板抗拉力相差很小;在无重土中的平板在加载初始即与土体脱离时,方板的承载力略低于圆板。大变形分析给出的立即脱离承载力系数与模型试验数据基本吻合,而小变形有限元与下限分析忽略了方形平板锚的长距离上拔过程对其抗拉力的影响,可能高估深锚的承载力。改进估计方形平板锚抗拉承载力的简化方法,方便于工程应用。

Based on the mesh regeneration and stress recovery of modified REP technique,a three dimensional large deformation finite element（FE） approach is presented to study the interaction between the cohesive soil and square plate anchors subjected to the pulling-up force.Different from traditional small-strain FE methods,large deformation analyses can simulate anchors’ pulling out process completely.If the soil beneath the anchor is always attached to the anchor base,the uplift capacities of square anchors are found to be very close to that of circular anchors.Once an anchor in the weightless soil is pulled up,the anchor base separates with soil immediately.In such case,large deformation analyses show the breakout capacity factor of square anchors is slightly lower than circular anchors.The breakout factors from large deformation analyses agree well with model test data.Both the small strain FE and lower bound theorem neglect the effect of anchor’s large displacement on the uplift resistance,tending to overestimate the capacity of deep anchors.A simplified method is developed to estimate the uplift capacity of square anchors for industrial applications.