An Experimental Study on Frictional Properties of Concrete Pipe-Soil Interface

In the construction of pipe jacking, the calculated jacking force is often greater than the actual measured value. In particular, the deviation between calculated and actual frictional resistance is large. Moreover, during the jacking process, the complex frictional behavior between the pipe and soil has not been fully understood. Therefore, this work aims to reveal the frictional properties and calculate the friction coefficient of the concrete pipe-soil interface. To that end, the frictional behavior and mechanical mechanism were investigated between seven types of soil and concrete pipe under different contact conditions (primarily considering three factors of shear rate, normal stress, and slurry lubrication) through direct shear tests. The test results show that the residual shear stress of the concrete-sand interface increased and then decreased with the increase in sand particle size. With the increase of normal stress, the shear displacement when the shear stress of the concrete-soil interface reaches the peak or stable value increases. Under the low normal stress, the shear rate has little effect on the shear stress of the concrete-soil interface. Under slurry-lubricated conditions, the shear stress of the concrete-sand interface can be reduced by 60%-80%, and the shear stresses of the concrete-silty clay interface and the concrete-clay interface can be reduced about 90%.