桩周土开挖状态下钢筋混凝土桩稳定性研究

开展了桩周土开挖状态下钢筋混凝土桩受压稳定性试验，通过改变桩的配筋率、边长、受压偏心距和桩身加支撑等参数，研究桩的受压稳定性变化规律。研究结果表明，桩开挖深度由0.6m增加到1.8m时，桩的极限荷载降低11%~32%；桩初始偏心距由0增大到50mm时，桩的极限荷载降低42%~68%。在相同开挖深度条件下，随着桩配筋率的增加、桩截面尺寸的增大以及设置桩身支撑，其受压极限荷载明显增大。其中，桩截面尺寸由80mm增大到120mm能使极限荷载提高74%，效果最好。基于试验结果，提出了钢筋混凝土桩受压承载力的计算方法。将所提出的计算方法得到的桩身承载力与试验结果比较可知，轴心受压时，计算值与试验结果平均偏差仅为3.6%；偏心受压时，在桩的开挖深度较大时吻合较好，而开挖深度较小时会出现较大的偏差。

Study of reinforced concrete pile buckling stability under excavation conditions

The pressure test of reinforced concrete piles in excavation conditions was conducted to find the rule of pile buckling stability. Different influence facts were considered including ratio of pile reinforcement, pile section size, eccentric distance of pile and the existing of horizontal support. The test results indicate that the pile stability decreases by 11%-32% with the excavation around the pile growing from 0.6m to 1.8m, and decreases by 42%-68% with the eccentric distance of pile increasing from 0mm to 50mm. Under the same excavation condition that the depth, with larger ratio of reinforcement, section size, and the existing of horizontal support during deep excavation, the pile stability increases as well; among them the increase of section size from 80mm to 120mm is the most effective, which increases the pile stability by 74%. The pile stability calculation formula was put forward, which exhibits consistent tendency with the test results, and the average difference is 3.6% in the case of axial compression. In the case of eccentric compression, the propose calculation formula agrees well with the test results for deep excavation, but the difference is relatively large for shallow excavation.