大断面钢结构顶管纵向力时变规律研究

Temporal variation laws of longitudinal stress of pipe jacking with largesection steel structure

顶管隧道断面上纵向力的大小,一方面影响结构稳定和施工安全,另一方面影响环缝止水垫的防水性能和环缝刚度。通过计算求解顶管隧道纵向力与摩阻力、掌子面压力以及止退反力之间的数学方程,建立了隧道断面纵向力随顶进里程的变化关系,并将理论解与现场试验实测结果进行了对比,二者具有良好的匹配性。分析结果表明:(1)管节断面纵向力随顶进里程的变化规律为一条逐渐收敛的波动曲线,并在隧道贯通后迅速降低。理论值与实测值具有良好的匹配性;(2)止退时及隧道贯通后断面纵向应力较小,不利于环缝防水,且隧道纵向刚度较小,易产生不均匀沉降;(3)止退装置弹性系数、顶进里程、隧道尺寸及隧道埋深是顶管断面纵向应力的重要影响因素,且均呈现不同程度的正相关关系。

The longitudinal force on the section of pipe jacking tunnel affects the structural stability and construction safety as well as the waterproof performance and joint stiffness of the circumferential weld. By calculating and solving the mathematical equations for the longitudinal force, the frictional resistance, the force on the face and the back-stopping force, the relationship between the longitudinal force of tunnel section and the jacking mileage is established. The theoretical solution is compared with the field test results, and they are in good agreement. The analysis results show that:(1) The variation law of longitudinal force of pipe section with time is a gradually convergent curve, and decreases rapidly after the tunnel is coalescent. The theoretical values match well with the measured ones.(2) The longitudinal stress on the section at the stop and after the tunnel coalescence is small, which is not conducive to the annular seam waterproofing, and the longitudinal stiffness of the tunnel is small, which is easy to produce differential settlement.(3) The elastic coefficient of the back-stopping device, jacking mileage,size and buried depth of tunnel are the important influencing factors for the longitudinal stress on the section of pipe jacking,and they are positively correlated to different degrees.