隔离桩法消减桩基边载负摩阻力的试验研究

Research on Shielding Piles for Reducing Negative Skin Friction on Piles under One-side Surcharge Loading

土表边载作用下黏土中桩基多承受复杂的负摩阻力作用,可能造成桩基或上部结构损坏,研究隔离桩法消减边载负摩阻力作用具有重要的意义。设计并开展了黏土中单侧堆载作用下桩基模型试验,测定了桩身应变、桩顶位移以及土表沉降,研究了隔离桩间距、刚度、桩型对工程桩轴力及弯矩的影响及其随黏土固结的时间效应。试验结果表明,工程桩弯矩较快达到峰值并随固结时间而减少,桩顶水平位移较桩顶沉降更早趋于稳定;设置隔离桩可有效降低工程桩轴力、弯矩和边载负摩阻力,当桩间距大于4D后,对轴力的消减效果受桩间距的影响降低;增大隔离桩抗弯刚度、近土表处加设翼板可以有效减少边载负摩阻力作用,当隔离桩间距较大时,建议在隔离桩侧加设翼板以提高阻隔效果。

Piles in clay under side load are often subjected to complex negative friction,which may cause damage to pile foundation or superstructure,therefore,it is of great significance to study the effect of isolation pile method of reducing negative friction under side load.Model tests of pile foundation under unilateral overloading in clay are designed and carried out.The pile strain,pile top displacement and soil surface settlement are measured.The effects of spacing,stiffness and pile type of isolation pile on the axial force and bending moment of engineering pile and the time effect of consolidation with clay are studied.The results show that the bending moment of engineering pile reaches the peak rapidly and decreases with consolidation time,and the horizontal displacement of pile top tends to be stable earlier than the settlement of pile top.The isolation pile can effectively reduce the axial force,bending moment and side load negative friction resistance of the engineering pile.When the pile spacing is more than 4 days,the reduction effect of the axial force is reduced by the influence of the pile spacing.Increase the bending stiffness of the isolation pile and add a wing near the soil surface can effectively reduce the side load negative friction.When the spacing of the isolation pile is large,it is suggested to add a wing at the side of the isolation pile to improve the isolation effect.