软土地区桩端后注浆桩承载性状对比试验研究

COMPARISON TEST STUDIES ON THE LOAD BEARING CHARACTERISTICS OF POST-GROUTED BORED PILES IN SOFT SOIL

桩端后注浆技术是在通过预埋的压浆管对桩底压注水泥浆液,从而减少桩底沉渣和桩周泥皮的负面影响,在工程上逐渐得到广泛应用。结合宁波软土地基中某工程桩基静载荷试验,分析2根相邻后注浆和未注浆试桩的承载性状;通过对桩身预埋钢筋应力计的测试,对后注浆和未注浆桩的桩身轴力传递特性和桩侧阻力发挥特性进行比较分析研究。表明桩端后注浆不仅能提高端阻,还能提高桩端以上一定范围内土层的侧摩阻力,同时,后注浆桩的单桩极限承载力约为未注浆桩的2.5倍。根据以上研究结果表明,桩端后注浆技术能有效改善桩土界面条件,提高单桩承载力和减小桩基沉降。

Post - grouting technique injects cement slurry into pile toe along its embedded steel pipe. It can reduce detritus of pile toe and mudcake and is used widely. It is necessary to understand fully the bearing capacity of post - grouted pile. Traditional design method of pile foundation is usually adopted and does not accord with the practical situation. Based on the results of static loading tests of two piles （ one is post - grouted and the other not ）, the bearing properties of the two piles are analyzed comparatively. The load transfer mechanism, such as the axial load and the skin friction distribution law, is studied with the stress gages. It is found that the bearing capacity of the post - grouted pile is about 2.5 times larger than that of the prove the toe resistance and skin friction. It can improve the ordinary one. The post -grouting technique can imcharacteristics of the interface between pile and soil, and increase the bearing capacity and decreases the settlement of pile effectively