多排微型抗滑桩极限抗滑力的数值模拟研究

Numerical study of ultimate anti-sliding force of multi-row micro anti-slide piles

对多排微型桩群在土体水平位移作用下的响应开展数值模拟研究,微型桩的建模充分考虑了其塑性变形的特性,并通过对已有的桩抗弯试验建立精细化有限元模型获得了桩体参数。在分析微型抗滑桩响应的基础上,推导了适用于微型抗滑桩的简化极限抗滑力计算公式,研究了微型桩排距和滑动面摩擦因数的影响。结果表明:多排桩能调动相对单排桩更大深度范围的桩土相互作用,结构整体刚度更高,但同时群桩效应降低了桩土相互作用力,多排桩中单桩抗滑力仅为单排桩情况下的50%~70%;滑动面摩擦因数对多排桩的影响大于单排桩,增加该系数明显降低了桩土相互作用力,提高了桩的影响深度范围,导致抗滑力降低;增大排距可整体上提高多排微型桩的抗滑力,当排距小于7倍桩径时,增大排距主要降低了桩的影响深度范围,而当排距大于7倍桩径时,则主要是通过改变桩土相互作用力的分布来增加抗滑力;所提出的桩抗滑承载力计算公式较好地反映了微型桩的受力特征,具有进一步研究和推广的价值。

A numerical simulation study was carried out on the response of a multi-row micro-pile group subjected to soil lateral displacement.The plastic deformation characteristics of micro-pile was considered in the numerical model,and the pile parameters were obtained by performing a refined finite element model against some published pile bending tests.Based on the analysis of the micro anti-slide pile response,a simplified formula for calculating the ultimate anti-sliding force was deduced.The influence of the row spacing and the friction coefficient of slip surface were studied.The results show that in the multi-row case,the pile-soil interaction is mobilized in a larger depth range than the case of a single row of piles,and the overall stiffness of structure is higher.However,the pile group effect reduces the pile-soil interaction force.As a result,the anti-sliding force of a single pile in the multi-row structure is only 50%-70%of that of the case of a single-row.The influence of the slip surface friction coefficient is greater on multi-row piles than on single-row piles.Increasing friction coefficient significantly reduces the pile-soil interaction force and increases the pile influencing depth range,which result in the reduction of anti-sliding force of pile.Increasing the row spacing can improve the overall resistance of the multi-row micro-pile structure.When the row spacing is less than 7 times of pile diameter,increasing the row spacing mainly reduces the pile influencing depth range.While the sliding resistance is mainly increased by the variation of the pile-soil interaction force distribution when the row spacing is greater than 7 times of pile diameter.The proposed calculation formula of the bearing capacity of anti-sliding pile can well reflect the force characteristics of the micro-pile,which is worth to be further researched and promoted.