砂土与混凝土顶管界面摩擦特性试验研究

为了揭示不同工况下混凝土顶管-砂土接触面剪切摩擦特性，确定管土、管浆摩擦系数，为顶管施工参数的选取及顶进力的计算提供指导与参考。采用直剪试验研究了5种砂土在不同法向压力、不同剪切速率及不同润滑状态下与混凝土管接触面的摩擦特性。试验结果表明:随着砂土颗粒粒径的增加，砂土与混凝土接触面剪切应力稳定值降低。随着法向应力的增加，砂土界面剪切应力达到峰值或稳定值时的剪切位移增加，同时界面剪切应力-剪切位移曲线的应变软化特性逐渐减弱，应变硬化趋势逐渐增强。无润滑条件下，随着法向应力的增加，剪切应力稳定值增量基本保持稳定或略有降低，泥浆润滑条件下，剪切应力稳定值增量增大；在较低法向压力下剪切速率对砂土剪切应力的影响较小；泥浆润滑条件下，砂土与混凝土接触面剪切应力可降低70%~80%，随着法向应力的增加，润滑效果降低。 

Experimental study on interface frictional property between sand and concrete pipe jacking

To reveal the shear friction mechanical mechanism between concrete pipe jacking and sand, obtain the friction coefficient of pipe-soil and pipe-slurry, and provide guidance and reference for the selection of pipe jacking construction parameters and the calculation of jacking force.To that end, the shear friction behavior and mechanical mechanism were investigated between 5 types of sands and concrete pipe under different normal pressure, shear rate and lubrication state. The test results show that the stable value (residual value) of shear stress at the concrete-sand interface increases first and then decreases with the increase of sand particle size. With the increase of normal stress, the shear displacement when the shear stress of the concrete-sand interface reaches the peak or stable value increases. Meanwhile, the strain softening characteristic of the shear stress versus shear displacement curve gradually weakens and the strain hardening trend gradually obvious. Without lubrication, as the normal stress increases, the increment of shear stress stability value remains stable or slightly decreases. With slurry lubrication, the increment of shear stress stability value increases. Under lower normal pressure, the shear rate has little effect on the shear stress of sand.When using slurry lubrication, the stable value of shear stress at the concrete-sand interface can be reduced by 70%-80%, and the lubrication effect decreases with the increase of normal stress.