边载作用下的负摩阻力和群桩效应研究

Variation of negative friction resistance of pile group under side load

桩基础在堆载或边载存在时可能会出现负摩阻力,而负摩阻力又会影响桩基础的上部结构,如建筑物、轨道、桥面等结构的变化,并且对施工过程提出了更高的要求.目前对堆载情况下的桩基负摩阻力研究比较充分,但对边载下群桩负摩阻力变化规律的研究还有待深入.本文使用ABAQUS数值分析软件对不同边载、不同桩间距下的群桩负摩阻力变化情况进行有限元模拟,得出群桩中基桩下拉荷载的变化情况,再利用群桩效应系数公式与遮挡系数公式分析不同条件下群桩效应的变化情况.模拟结果表明,增大边载会引起各桩的下拉荷载变大,但群桩系数变小,遮挡系数变大,显示群桩效应在增强;增大群桩的桩间距同样引起各桩下拉荷载变大,此时群桩系数变大,但遮挡系数变小,显示群桩效应减弱,群桩负摩阻力变大.

Pile foundation under pile load or side load will produce negative friction resistance,it is easy to use the pile foundation of buildings,roads,Bridges and other projects have serious consequences.The research on negative friction resistance of pile foundation under pile load has been more and more sufficient,but the research on the change law of negative friction resistance of pile group under side load is still to be developed.In this paper,ABAQUS numerical analysis software is used to conduct finite element simulation of the change of negative friction resistance of pile group under different side loads and different pile spacing,so as to obtain the change of pull load of foundation piles in pile group.Then,the formula of pile group effect coefficient and the formula of shelter coefficient are used to analyze the change of pile group effect under different conditions.With the increase of side load,the pull-down load of each pile becomes larger.The simulation results show that the increase of side load will lead to the increase of the pull load of each pile,but the pile group coefficient is larger at the same time the shielding coefficient is larger,indicating that the pile group effect plays well,and the increase of pile group spacing will also lead to the increase of the pull load of each pile.but at this time,the pile group coefficient becomes larger and the shielding coefficient becomes smaller,indicating that the pile group effect is weakened and the negative friction resistance of pile group becomes larger.