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基于Pasternak弹性地基梁理论对管棚预支护体系的力学行为进行分析,并与现场测试数据进行对比验证;同时,对不同管棚长度、钢管直径及搭接长度条件下管棚的加固效果进行了分析。结果表明:Pasternak模型能较好地反映管棚在隧道开挖过程中的真实力学行为;管棚的临界长度约为1.5倍开挖高度,当管棚长度超出临界长度后,其对控制开挖面稳定及地层变位的效果不太明显;当钢管直径超过159 mm时,钢管直径的增加对控制开挖面顶部围岩的变形意义不大,目前工程中采用108~159 mm的钢管直径是适宜的。
Based on the Pasternak elastic foundation beam theory, the mechanical behaviors of the pipe roof pre-supporting system are analyzed and verified with the field test data. At the same time, the reinforcement effect of the pipe roof under different pipe shed length, pipe diameter and overlap length analysis. The results show that the Pasternak model can well reflect the true mechanical behavior of pipe shed in tunnel excavation. The critical length of pipe shed is about 1.5 times excavation height. When the pipe shed length exceeds the critical length, The effect of surface stability and formation displacement is not obvious. When the pipe diameter exceeds 159 mm, the increase of pipe diameter has little effect on the deformation control of the surrounding rock at the top of the excavation face. At present, the diameter of the pipe with 108 ~ 159 mm is suitable.