大直径群桩基础承载特性现场试验及数值模拟

Field test and numerical simulation study on bearing capacity of large diameter group pile foundation

大直径群桩基础具有承载力高的特点,在软土区大型工程基础中具有广阔的应用前景。基于某桥梁群桩基础工程的单桩现场竖向静载试验数据,运用ABAQUS试算拟合土体参数,运用所得土体参数对基桩水平荷载作用下的承载特性进行计算和分析,并对承台-群桩基础在竖向和水平荷载下的承载特性进行了研究。研究表明:当最大竖向荷载作用于承台-群桩基础时,承台最大位移为84.83 mm,按照位移控制原则计算得到群桩效应上限值为83%,下限值约为62.8%;竖向荷载作用下群桩中各桩的沉降值存在差异,中心桩最大,其次是边桩,角桩沉降最小,且随着荷载的逐渐增大,角桩与边桩和中心桩位移差量呈现出先增大后减小的变化趋势;最大水平荷载作用于承台-群桩基础时,基础水平位移水平影响范围约为1.5倍承台边长,最大影响深度约为1.5倍承台边长。桩间土体在地表以下0.5倍承台边长范围内呈现出拉-剪应力状态。对群桩在水平和竖向荷载作用下承载特性的分析及其相关结论,可为相关工程设计借鉴。

Large-diameter pile group foundations have the characteristics of high bearing capacity,and have broad application prospects in large-scale engineering foundations in soft soil areas.Based on the field test data of vertical bearing capacity of a bridge group pile foundation,the ABAQUS numerical calculation platform is used to calculate and fit the soil parameters.Based on the soil parameters obtained from the fitting,the bearing characteristics of the piles under the horizontal load are calculated and analyzed,and the bearing characteristics of the group pile foundation under vertical and horizontal loads are also studied.The results show that when the maximum vertical load acts on the cap-pile group foundation,the maximum displacement of the cap is 84.83 mm,and according to the displacement control principle,the upper limit of the pile group effect is 83%,and the lower limit is about 62.8%.Under the vertical load,there are differences in the settlement value of each pile in the pile group,the center piles are the largest,followed by the side piles,the corner piles have the smallest settlement.With the load gradually increased,the displacement differences of the corner piles,the side piles and the center piles show a trend of first increasing and then decreasing.When the maximum vertical load is applied to the group pile foundation,the horizontal influence range of foundation horizontal displacement is about 1.5 times of the side length of cap,and the maximum influence depth is about 1.5 times of the side length of cap.The soil between piles shows tension shear stress in the range of 0.5 times of side length of cap below the ground surface.This paper analyzes the bearing characteristics of pile groups under horizontal and vertical loads and its conclusions can be used for reference for relevant engineering design.