某工程人工挖孔桩竖向静载试验研究与设计

Design of vertical static loading test on artificially punched piles in an engineering project

根据某工程2根人工挖孔桩静载试验的结果,预测了桩的极限承载力,并根据侧阻力随荷载和位移增加的变化情况,证明了护壁的存在对侧阻力后期的发挥会产生不利影响,同时也说明目前设计时不计桩侧摩阻力有一定的合理性。对桩端及桩侧承载力所占的比例进行了分析,分析结果表明,如果孔桩进入强度较好的风化岩以上岩土层时,不设护壁时的桩侧阻力相当可观,设计时应当考虑其桩侧阻力的贡献;如果设计扩大头将破坏其侧阻力的发挥,甚至会因桩端土层的软化而导致工程事故发生,造成工期延误和不必要的经济损失。基此,文章最后提出了挖孔桩优化设计和施工工艺创新的思路。

Based on the static loading test results of two artificially punched piles in an engineering project, the ultimate bearing capacity of the piles was estimated. In relation to the changes of side resistance with increasing load and displacement, it was confirmed that the existence of a protecting rampart had negative effect on side resistance in its later stage. Meanwhile, the rationality of disregarding pile side frictional resistance at present design was illustrated. The beating capacity ratios of the pile end and pile side were analysed. The results indicate that when the pile enters into the rock- soil layer on top of hard weathered rock, there is a considerable side resistance to the pile under the condition of no rampart. Thus the pile side resistance should be considered in the test design. On the other hand, enlarging pile top weakens the effect of pile side resistance, which may even cause accidents due to the softening of pile top soil layer and may result in delay of the engineering projects and economic losses. An innovative thinking was proposed in this paper to optimize the design and construction of the artificially ounched oiles.