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.