大口径新型顶管力学行为现场试验研究
Site-based researches on mechanical behavior of new large-diameter pipes during pipe jacking
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摘要: 通过对新型预应力钢筒混凝土顶管(JPCCP)开展现场试验,得到了在施工荷载、水土压力等三维荷载作用下顶管各部位的应变时程响应;同时也获得了顶进过程中管-土接触应力时程变化。根据对数据的分析,得出预应力钢筒混凝土顶管具有较大的纵向抗压刚度,而纵向抗拉刚度不足。由于预应力的效应,内层混凝土与中间层混凝土能够承受较大的环向拉应力。通过对管节的纵向受力分析,计算出管-土平均摩阻力随顶进距离的变化规律,结合施工记录得出平均摩阻力随顶进距离先增大后减小,最小值为1.27 kPa;同时,施工顶进间隔越短,平均摩阻力越小。此外,实测结果表明,管-土接触应力对管节运动较为敏感,最大瞬时值可达500 kPa;施工结束后,接触应力沿管周分布并不对称或均匀,但与实测管节环向应变分布对应。Abstract: The strain responses of each part of the jacking prestressed concrete cylinder pipe (JPCCP) as well as the pipe-soil pressure under three-dimensional construction loads and water-soil pressure are measured in site. It is shown that the axial compressive stiffness of the JPCCP is large enough to sustain jacking forces. Due to the effects of prestressing, it can bear large tensile stress in the hoop. However, the axial tensile stiffness of the JPCCP is insufficient. Through the force analysis of different pipes in axial direction, the friction force between pipe and soil is figured out, which shows that the shorter the jacking intermittent, the less the average friction force. Otherwise,the pipe-soil pressure is sensitive to pipe motion, and the instantaneous maximum value is 500 kPa. After construction, the distribution of contact stress along the tube is not symmetrical or uniform but coincides with the measured strain of the pipe joint ring.