黄土填方地基中微型钢管桩承载性状试验研究

Experimental study on bearing characteristics of micro steel tube piles in loess fill foundation

目前对于黄土填方场地微型钢管桩桩基性能的研究非常匮乏。依托某实际加固纠偏工程,在黄土填方场地制作三根微型钢管桩试桩,在试桩桩身混凝土中布置混凝土应变计,进行现场单桩静载试验。实测结果研究表明:(1)在一些特定场合,尤其是在施工场地狭小,工程条件复杂的情况下,微型钢管桩可用于黄土填方场地较大荷载的建筑物基础纠偏加固中,并且在黄土填方场地具有较高的承载力。(2)黄土填方地基中微型钢管桩的Q–s曲线呈缓变型,当加载至最大荷载时,都没有出现明显向下的弯折段。(3)微型钢管桩在黄土填方场地其承载力介于材料破坏和失稳破坏之间,约为材料破坏的62%,是失稳破坏的1.76倍,桩身挠曲而产生过大沉降是导致试桩破坏的主要原因。(4)在黄土填方地基中确定30~40m长的微型钢管桩单桩竖向极限承载力时,建议将Q–s曲线和s–lgt曲线相结合,同时考虑桩顶沉降值,这样才较为合理。

The researches on the performance of micro steel tube piles for the loess fill foundation are very scarce. Based on a practical reinforcement and slant rectification project, three micro steel tube piles are used as the test piles in the loess fill site. The single-pile static load tests with concrete strain gauges arranged on concrete of test piles are performed. The results show that:(1) In some cases, especially in the narrow construction site under complicated engineering conditions, the micro steel tube pile can be used for reinforcement and slant rectification of foundation of high load-support and has higher bearing capacity.(2) The Q–s curve of the micro steel tube piles slowly changes in loess fill site. Under the maximum load, there is no obvious downward bending section.(3) The bearing capacity of micro steel pipe piles in the loess fill foundation is between the material damage and the unstable failure, about 62% of the material damage and 1.76 times the unstable failure. The settlement caused by pile deflection is the uppermost reason for the failure of the test piles.(4) When defining the vertical ultimate bearing capacity of single pile of the micro steel tube piles 30~40 meters in length in loess fill foundation, it is recommended to combine the Q–s curve and the s–lgt curve, and to consider the settlement value of pile top, and it is more reasonable.