Experimental study on shear properties of soil-rock interface of sisal fiber composite material

In order to study the influence of sisal fiber and interface roughness on the shear mechanical properties of soil-rock interface, concrete modules with rough surface were used as the rock surface similar material and a series of indoor shear tests were carried out. Combined with the SEM test, the mechanism of sisal fiber participating in the strengthening of the interface is further analyzed. The results show that sisal fiber can improve the shear mechanical properties of soil-concrete interface by improving the cohesion. The addition of 0.8% by weight increases the interfacial bond strength of soil-cement interface by 0.8-5 times and the internal friction angle by 0.1-0.2 times. The interface roughness mainly enhances the shear mechanical performance of the interface by improving the bond strength. For an interface roughness of 6.5 mm, the increase of interfacial bond strength ranges from 7 kPa to 15.5 kPa, resulting in an improvement of 0.2-3 times. The enhancement of roughness on the shear mechanical performance of the soil-cement interface exhibits two distinct patterns for the plain soil interface and the fiber-reinforced interface. Regarding the relationship between interfacial bond strength and roughness for the fiber-reinforced interface, the optimal value of roughness appears within a smaller range (0-2.5mm).