静压桩残余应力对极限承载力影响

Influence of residual stress of jacked pile on ultimate bearing capacity

为研究静压桩回弹特性,明确静压桩残余应力性状,使静压桩承载力能够得到有效发挥,通过静压桩沉桩及静载荷试验,结合有限元模拟方法,对不同沉桩速率和卸荷速率作用下静压桩的回弹特性进行分析,总结桩端残余应力对静压桩极限承载力的影响规律。结果表明:卸荷过程中桩体回弹量占桩体总沉降量的80%,卸荷完成桩体回弹位移逐渐稳定;沉桩结束后,桩周土体应力最大达到被动土压力的4.5倍,卸荷后浅部土体桩周侧压应力消散程度大于深部土体;桩端土体应力消耗越多,桩端残余应力越小,卸荷后桩端土体回弹量越多;沉桩速率和卸荷速率增加都会导致桩端残余应力减小,从而桩端土体能够提供的承载力降低,致使桩体承载力降低。研究认为静压桩残余应力是影响承载力的主要因素,卸荷速率对静压桩残余应力的影响最为明显。

In order to explore the rebound properties and the residual stress characteristics of jacked piles,so as to make full use of its bearing capacity,the rebound characteristics of jacked piles under different pile sinking rates and unloading rates are analyzed,through the jacked pile sinking and static load test,combined with the finite element simulation method,with the influence of pile end residual stress on the ultimate bearing capacity of jacked piles summarized.The results show that the rebound amount of the pile body accounts for 80%of the total rebound amount of the pile body during the unloading process,and the rebound displacement of the pile body gradually stabilizes after unloading.After the pile sinking,the maximum stress of the soil around the pile reaches 4.5 times of the passive earth pressure.After unloading,the lateral pressure stress dissipation of the shallow soil around the pile is greater than that of the deep soil.The more the stress consumption of the soil at the pile end,the smaller the residual stress at the pile end,and the more the rebound of the soil at the pile end after unloading.The increase of pile sinking rate and unloading rate would lead to the decrease of residual stress at the pile end,and reduce the bearing capacity provided by the soil at the pile end,resulting in the decrease of bearing capacity of the pile.It is concluded that the residual stress of the jacked pile is the main factor affecting the bearing capacity,and the unloading rate has the most obvious influence on the residual stress of the jacked pile.