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提出在桩顶(坑底)位置处设置钢筋计测试下部桩身抗拔承载力的钢筋应力测试法试桩,采用有限元软件ABAQUS对4类试桩(常规试桩、钢筋应力测试法试桩、套管试桩及坑底试桩)开展数值分析,总结不同试桩下抗拔桩荷载传递规律及其工作机理。在此基础上采用所提出的钢筋应力测试法试桩在不同有效桩长及开挖深度下进行抗拔桩承载性能分析,结果表明:抗拔桩有效桩长越长,与坑底试桩抗拔桩极限承载力相比,基坑底面处钢筋拉力的损失比例越小;随着开挖深度的加大,与开挖后抗拔桩承载力相比,测试得到的钢筋拉力的损失比基本在10%~15%范围变化。在实际工程应用中,建议可按所提出的钢筋应力测试法测试抗拔桩下部桩身承载力,考虑开挖的影响,按10%~15%来折减抗拔桩的极限承载力。
This paper puts forward the test method of steel bar stress which is used to test the pullout resistance of the lower part of the pile under the top of the pile (bottom of the pit), and uses the finite element software ABAQUS to test four kinds of test piles , Casing test pile and pit test pile) to carry out numerical analysis to summarize the law of load transfer and its working mechanism of anti-pull pile under different test pile. On this basis, the proposed test method of steel bar stress test is used to analyze the bearing capacity of pile under different effective pile lengths and excavation depths. The results show that the longer the effective pile length of pile is, Compared with the ultimate bearing capacity of piles, the proportion of the loss of the steel bar tensile strength at the bottom of the foundation pit is smaller. With the increase of the excavation depth, the loss of the tensile strength of the steel bar obtained after the excavation is lower than that of the basic In the range of 10% to 15%. In practical engineering application, it is suggested that the load-bearing capacity of the lower part of the pile can be tested according to the proposed method for stress measurement of reinforced bars. Considering the influence of excavation, the ultimate bearing capacity of the pile can be reduced by 10% ~ 15%.