软土地区桩端后注浆灌注桩竖向承载性能试验研究

Experimental study on vertical bearing performance of base post-grouted cast-in-place plies in soft soils

钻孔灌注桩因施工工艺的限制,桩底沉渣较多且难以清理,这会降低桩基的承载性能,而桩端后注浆技术通过压浆管对桩底压注水泥浆液,从而减少桩底沉渣等的负面影响,并能提高基桩的承载能力。结合软土地区中某工程的试桩在桩端注浆前后的静载试验成果的对比分析,研究其在注浆前后的承载性能变化;并通过桩身预埋钢筋应力计的测试结果分析,研究桩端后注浆对桩身轴力传递特性、桩端阻力及桩侧摩阻力发挥性状的影响。研究结果表明,桩端注浆不仅能提高桩端承载力,还能提高一定范围土层内的桩侧摩阻力,并能有效减少桩的沉降,桩端后注浆后的单桩极限承载力能较注浆前的得到明显的提高。

Bottom sediment of piles is often thick and impossible to clear completely because of the limitation in construction techniques of bored cast-in-place piles. It will reduce the bearing capacity of piles. The base post-grouting techniques inject cement slurry into pile bottom with its embedded pipe in order to reduce the detritus of pile bottom sediment and improve the bearing capacity of foundation piles. Combined with the static load test results of two piles with or without base post-grouting, the bearing performances of piles are analyzed comparatively. The load transfer mechanism and the behavior of base resistance and skin friction resistance of the piles before and after post-grouting are studied by the comparisons of the test results with the stress gages embedded in the pile shaft. The results show that the base post-grouting technique can improve the base resistance and the skin frictional resistance, and reduce effectively the settlement of foundation piles. The ultimate vertical bearing capacity of piles with base post-grouting is much larger than that without base post-grouting.