黄土地基中超长钻孔灌注桩承载性状试验研究

为了研究黄土地基中超长钻孔灌注桩的承载性能、桩身轴力传递规律、桩侧阻力和端阻力的发挥性状,对西安地区6根超长钻孔灌注桩进行单桩静载荷试验,采用滑动测微计测试每米范围内桩身轴力的变化。可以发现,黄土地基中超长钻孔灌注桩的Q-S曲线呈缓变型,在最大荷载时都未达到破坏状态;桩身轴力传递规律和桩侧阻力的发挥与成孔工艺、桩长、桩周土层性质密切相关。由于黄土地基中的粉质黏土和粉土具有强结构性,测试得到的极限侧阻力远比规范值要大,使得黄土地基中超长钻孔灌注桩具有较大的承载能力,但桩端阻力和桩侧阻力并非同时发挥,建议在设计时考虑端阻力的发挥度,桩侧摩阻力和桩端阻力采用不同的分项系数。

Experimental study on super-long bored pile in loess

The vertical static load test is adopted to investigate 6 super-long bored piles in loess,in which the variation of axis force in piles is tested by sliding micrometer. Hence, the bearing capacity behavior , load transfer mechanism , the lateral friction and end bearing are researched in this paper. According to the test results, the Q—S curves of super-long bored piles are slowly varying.The boring method, pile length and soil around pile are all important to the load transfer mechanism and the action of lateral friction.For the natural structure of loess, the tested results are far larger than the standard values in code. As the result, the bearing capacity of super-long bored piles in loess is very well, while lateral friction and end bearing can not display simultaneously. It is necessary to adopt different coefficients of lateral friction and end bearing in practice.