滨海软土中超长后注浆灌注桩承载性能研究

依托天津某主塔楼桩基工程,通过双循环静载试验及试验数据的分析,研究了滨海软土中超长后注浆桩的承载性能。结果表明,超长后注浆桩的荷载-沉降曲线呈缓变型;回弹时桩侧摩阻力反向,使得在第二次循环开始时,部分桩段的桩身轴力大于桩顶荷载;桩身弹性压缩是桩顶产生沉降的主要原因;桩的承载力主要靠桩侧摩阻力承担,有效桩长段上部的侧摩阻力充分发挥。试验桩的端阻比还不足3%,更多表现出摩擦桩的特性。此外,对现有的几种单桩承载力计算方法及结果进行了对比分析,并对单桩承载力计算方法适用性进行了讨论,提出了在滨海软土单桩极限承载力计算时的桩侧摩阻力增强系数优化值,可为今后类似工程的设计施工提供参考。

Study on bearing capacity of super-long cast-in-place pile with post-grouting technology in coastal soft soil

The bearing capacity of super-long post-grouting pile in coastal soft soil was studied by the analyses of double-cycle static load test and test data,based on a pile project in Tianjin.Results show that:load-settlement curve of super-long post-grouting pile changes slowly;axial force of part pile is greater than pile load and negative friction appears at the begining of the second cycle,because friction changes direction during rebound;elastic compression is the main reason for the settlement of pile;the bearing capacity of pile mainly includes frictional resistance that has been fully exerted up the effective length;the end resistance ratio of the test pile is less than 3%,so the pile shows the properties of friction pile more.In addition,by comparing and analyzing the existing single pile bearing capacity calculation methods and their results,as well as their applicability discussion,the optimized value of the lateral friction resistance enhancement coefficient of the pile was proposed during the calculation of the ultimate bearing capacity of a single pile in coastal soft soil,providing a reference for the design and construction of similar projects in the future.