锤击预应力管桩内力测试及荷载传递试验研究

Internal Force Testing of Pile Shaft and Load Transfer Characteristics for Prestressed Pipe Pile Embedded with Hammering Method

锤击预应力管桩桩身量测元件埋设难度大、成活率低,限制了通过现场试验对预制管桩桩基设计参数、桩基受力性能的深入研究。为解决这一难题,对比分析已有预制桩桩身量测元件埋设方法,针对锤击预应力管桩的成桩特点,提出一种新型应变计埋设工艺,并在某高速铁路路基工程中实施了6根试验桩(共188个应变计),成活率达到90%。结合桩基的静载试验,实测不同荷载水平下桩身内力沿深度的分布规律,并通过对桩身轴力、桩侧摩阻力、桩端阻力、桩周不同土层侧摩阻力的综合分析,研究深厚软土地基中预应力管桩的荷载传递特征。试验结果表明,工作荷载(1200 kN)下,桩侧摩阻力占95.6%,桩的受力特性表现为纯摩擦桩;桩身上部3层土(约31.4 m)桩侧摩阻均达到其各自极限值,中下部土层均远小于其极限摩阻力。

It is difficult to embed the measuring elements for hammering prestressed concrete pipe-piles.The survival rate for the measuring elements is low,which limits the in-depth study of the design parameters and the mechanical properties of the foundation by field test.To solve this problem,a method and technique of installing concrete strain gauges along the shafts of precast concrete pipe-piles,according to characteristics of such piles driving method by hammer,had been studied and proposed in this paper.Six test piles and a total of 188 strain gauges were buried in the subgrade engineering of a passenger line,and the survival rate reached 90%.Based on the pile static load test,the method was effective for prototype testing;the load transfer mechanism of the precast pile was studied;and the behaviors of skin resistance and inner force were analyzed.The results show that,under the working load of 1200 kN,the pile side friction resistance accounts for about 95.6%of the total bearing capacity.According to the bearing characteristics of the pile,it can be regarded as pure friction pile.The pile side friction of the 3 layers of soil(about 31.4 m)reaches their respective limit values,and the middle and lower soil layers are far less than the limit friction resistance provided by the specification.