软土地层大直径曲线顶管隧道受力特性

为研究软土地层中大直径曲线顶管隧道受力特征,采用现场实测方法,对软土地层大直径曲线顶管的管壁接触压力、环向和纵向钢筋应力进行测试,并与已有文献研究进行对比分析.结果表明:顶管接触压力整体分布均匀,注浆对管壁接触压力影响较大,停机后接触压力略有减小;环向应力初期以受压为主,顶进后期逐渐转为受拉,整体分布特征不明显,纵向应力以拉应力为主,其变化主要由管道轴线偏移控制;管壁注浆后减阻效果明显,顶力与管侧平均摩阻力均显著降低.对土压力分布模式展开分析,发现顶管规范公式偏于保守;土柱理论由于未考虑卸荷拱效应,所得理论值较实测值偏大;太沙基理论与马斯顿理论与实际情况吻合较好.该研究结论可为实际工程提供参考.

Stress characteristics of large diameter curved pipe jacking tunnelin soft soil layer

At present, there are few researches on the variation law of pipe earth pressure and the distribution of relevant mechanical laws in China. Most of the domestic analyses are based on the previous studies of shield tunnel. Therefore, the analysis of the mechanical characteristics of pipe jacking tunnel has important practical significance and engineering application value. In this paper, the field measurement method is used to test the contact pressure, hoop and longitudinal reinforcement stress of the large-diameter curved pipe jacking in soft soil layer, and the results are compared with the existing literature. The results show that the overall contact pressure of pipe jacking is evenly distributed, the grouting has a great influence on the contact pressure of pipe wall, and the contact pressure slightly decreases after shutdown. In the initial stage, the hoop stress is mainly compressive, and in the later stage of jacking, it gradually turns to tensile, with no obvious overall distribution characteristics; in the longitudinal stage, the tensile stress is the main stress, and its change is mainly controlled by the deviation of pipeline axis. After grouting, the resistance reduction effect is obvious, and the top force and the average friction of the pipe side are significantly reduced. Based on the analysis of the earth pressure distribution pattern, it is found that the pipe jacking specification formula is more conservative; the theoretical value of the soil column theory is larger than the measured value because the unloading arch effect is not considered; the theory of Terzaghi and Marston are in good agreement with the actual situation, and the research conclusion can provide reference for the actual project.