盖挖地铁车站试验桩单桩承载力试验分析

Experimental Study on Bearing Capacity Test of Single Pile in Subway Station Constructed by Covered Top-down Excavation

盖挖地铁车站设计桩顶往往低于自然地面较多,当受条件限制无法进行基坑开挖时,需在自然地面上进行单桩承载力试验。由于设计桩顶以上的无效土层会对试验桩产生较大的摩阻力,会导致试验数据不准确。研究盖挖地铁车站试验桩单桩承载力试验存在的无效土层摩阻力问题,提出结合消阻双护筒的试验桩制作方法,并对试验桩单桩承载力进行试验分析。试验结果表明:单桩承载力可满足设计要求,双护筒可较好地解决试验桩无效土层的桩侧摩阻力消除问题,保证试验数据准确可靠。

The designed pile top in the cover excavation subway station is usually lower than the natural ground. When the foundation pit excavation is restricted by conditions,the bearing capacity of the single pile must be tested on the natural ground. The invalid soil layer above the designed top may generate greater friction resistance to the test pile,which leads to inaccurate test data. This paper studies the problem of invalid soil friction in the test of bearing capacity of single pile,puts forward the method for making test pile combined with the double steel casing,and analyzes the bearing capacity of the single pile. The test results show that the bearing capacity of the single pile meets the design requirement and the double steel casing can better solve the problem of the pile side friction resistance of the invalid soil layer,which ensures the accuracy and reliability of the test data.