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钉形水泥土搅拌桩是一种新型的地基处理方式。借助现场抽芯试验和标准贯入试验来检测桩身质量,通过2组单桩荷载试验研究了钉形搅拌桩的单桩工作性状。研究表明,钉形搅拌桩具有较高的单桩极限承载力,且沉降很小;受到桩身强度的限制,荷载沿桩身传递大致在桩身6m的深度范围内,6～9m的桩身轴力很小,但9m以下桩身轴力有少量的增加;由于桩径的变化,桩身应力在变径处发生了应力集中现象;同一深度处桩身应力随着荷载的增大而增大,扩大头上部应力的增加幅度较大,桩身下部的应力基本不变。基于现场试验结果和钉形搅拌桩的单桩破坏模式,修改了规范中钉形搅拌桩的单桩极限承载力理论计算公式中系数η的范围,对广州南沙地区钉形搅拌桩承载力的判定具有一定的指导意义。
Spike cement soil mixing pile is a new type of foundation treatment. With the help of the core-pulling test and the standard penetration test, the pile’s quality is tested. The working behavior of single-pile of the spike-shaped mixing pile is studied by two groups of single-pile load tests. The results show that the nail-shaped mixing pile has a higher ultimate bearing capacity of single pile, and the settlement is very small. Due to the limitation of the strength of the pile body, the load is transmitted along the pile body within the depth of 6m of the pile body. The axial force is very small, but the axial force of pile under 9m has a small increase; due to the change of pile diameter, the stress of pile body stress concentration occurs in the reducing place; the pile stress at the same depth increases with the increase of load Large, to expand the head of the larger increase in stress, the lower part of the pile stress is basically unchanged. Based on the field test results and the failure mode of single pile of the nail-shaped mixing piles, the range of the coefficient η in the theoretical calculation formula of the ultimate bearing capacity of the single-piles is modified to determine the bearing capacity of the spike-shaped mixing pile in Guangzhou Nansha area Has a certain guiding significance.