桩端压浆对超长大直径桩侧阻力的影响研究

Study on effect of base grouting on shaft friction of overlength large diameter pile

桩端压浆可大幅提高超长大直径桩侧阻力,且桩侧阻力的提高成为桩承载力提高的主要原因。桩土间存在一个软弱层(泥皮层),浆液在压力作用下总是沿着软弱面向上运动,并对桩侧土产生挤压,在使桩径扩大的同时,亦对桩周土体进行加固,从而使桩侧摩阻力提高。根据超长大直径桩工程实例的静载荷试验、标贯试验及CT检测结果证明,压浆后在桩端以上一定范围内桩周土强度提高,桩侧阻力提高12.39%～52.87%,侧阻力增量占总增量比例达56%～88%。

The shaft friction can be improved greatly by base grouting, and the increment is the major part of ultimate bearing capacity increment of the overlength large diameter pile. There is a weak layer between a pile and the soil around it, so the grout always flows upward along the weak layer, squeezing the soil to a larger diameter and improving the shaft friction. According to the results of the self-balanced static load testing method, the SPT test and the CT scanning test of a project with overlength large diameter piles, the strength of soils in a large range above pile- bases was improved and the shaft friction was increased 12.39 %-52.87 %, the ratios of shaft friction in the increment of ultimate bearing canacities was 56 %-88 %.