钢管桩加固饱和黄土隧道软基的试验研究

Experimental Study on Steel Pipe Pile Reinforcement of the Soft Foundations of Saturated Loess Tunnels

针对宝兰客专王家沟隧道饱和黄土软弱地基采取加固措施,通过4种不同含水率桩基填土的钢管桩室内模型试验和现场加固软基试验,分析了模型钢管桩和现场钢管桩单桩、复合地基的沉降特性,以及高含水率桩周土钢管桩应变特性。研究结果表明:随着桩周土含水率的增加,模型钢管桩的Q-S曲线由缓变型变为陡降型,沉降速率加快,极限侧摩阻力以幂函数规律递减,高含水率桩周土钢管桩沿桩长方向的应变随加载时间大致呈"B"状分布;根据现场试验,建议选用钢管桩复合地基加固王家沟隧道富水软弱地基,钢管桩以等边三角形布置,并根据规范给出用于设计参数的建议值。试验结果可为钢管桩加固软基室内试验和现场试验、施工提供参考依据。

As for the reinforcement measures for the soft foundation of saturated loess in the Wangjiagou tunnel on the Baoji-Lanzhou passenger dedicated line, laboratory tests containing 4 kinds of loess water content and field tests for reinforcing the soft foundation were conducted. The settlement characteristics of the model pile and the field single pile and composite foundation were analyzed, respectively, and the strain characteristics of the model pile were studied for the high water content of the loess. Conclusions could be summarized as follows： Q-S curves of the model piles change from a smooth shape to an abrupt shape with the increase of the moisture content in the soil around the pile, while the settlement rate of the pile becomes higher, and the ultimate side friction of the pile decreases, as the law of the power function. For the high water content of loess, the strains along the steel pipe pile dis- tribute in a ＂B＂ shape with the loading time. Based on the results of field tests, it is suggested that the steel pipe pile and composite foundation should be used for reinforcing the soft foundation of the Wangjiagou saturated loess tunnel, with steel pipe piles distributed as an equilateral triangle. The proposed design parameters for the piles are given according to the specifications. The experiment results provide a reference for laboratory tests and field tests of soft foundations reinforced by steel pipe piles.