风化岩基大直径灌注桩后注浆承载性能试验研究

基于6根全风化和强风化花岗片麻岩地基中大直径泥浆护壁钻孔灌注桩单桩竖向抗压静载荷试验及桩身力学测试，对其中3根试桩进行桩侧后注浆，对比分析了其承载性状、变形特性及影响因素，并将所得试验数据与勘察报告推荐值和现行规范推荐值对比。结果表明：大直径嵌岩泥浆护壁钻孔灌注桩长径比25~34与嵌岩深度5D~8D，Q-s曲线呈缓变型；经后注浆处理与未经桩侧后注浆处理的试桩相比，单桩极限抗压承载力提高1.40%~15.3%，最大沉降量降低35.1%~65.6%，回弹率提高13.1%~82.4%，控制桩顶沉降效果显著。在该试验条件下，6根试桩的承载力和变形特性受长径比和嵌岩深度影响较大。经桩侧后注浆处理的试桩，嵌岩段摩阻比和桩侧摩阻力分担比受长径比和嵌岩深度影响更小；6根试桩的桩端阻力分担比受嵌岩深度影响显著；未经桩侧后注浆处理的试桩，桩侧摩阻力分担比受嵌岩深度影响更大。

Experimental study on bearing behavior of large-diameter drilling piles with post grouting in decomposed rock foundation

Based on the vertical compressive static load and pile mechanics tests of 6 large diameter mud-walled bored piles in fully weathered and strongly weathered granite gneiss foundation, including three post-grouting piles in side, the bearing behavior, deformation properties and impact factors are analyzed and the corresponding test data are then compared with the current recommended value of code and survey report. The results show that the Q-s curves of the large-diameter rock-embedded mud-walled bored piles, which are with length-diameter ratio of 25~34 and rock-embedded depths of 5D~8D, present slow type. Compared with no post-grouting piles, the ultimate compressive capacity of post-grouting piles increases by 16.7%~25%, the maximum settlement decreases by 35.1%~65.6%, and the rebound rate increases by 13.1%~82.4%. Besides, the control effect of pile top settlement is remarkable. Under the experimental conditions, the bearing capacity and deformation characteristics of the six test piles are greatly affected by the aspect ratio and the rock-embedded length. Nevertheless, the side resistance in rock-embedded section and side-resistance sharing ratio of the grouting piles is less influenced by the aspect ratio and the rock-embedded depth. The end-resistance sharing ratio of the six test piles and side-resistance sharing ratio of no post-grouting pile is highly affected by the rock-embedded depth.