Abstract: In order to reveal the cohesive failure mechanism of the second interface of anchor system in earthen sites, two groups of 30 soil-grout interface samples are designed to carry push-out test in laboratory with different bore wall roughnesses and mixture ratios of grouting materials. The second interface properties are studied relying on the independently-developed pressure testing machine and sample preparation device. The results show that the load-slip relation curve has obvious peak strength. The 30 cm anchorage length can provide shear stresses of 0.08～0.26 MPa on smooth hole wall and 0.26～0.46 MPa on thread hole wall. The shear strength of the thread interface has increased by 4.21 times in maximam. The shear strength of samples in two groups is almost the same by the increase ratio of the calcined ginger nuts (CGN). The character of smooth/thread interface is strain hardening/softening in shear-slide curves. According to bond stress-slip relationship model, the fitting curves present good agreement with the test results. The research lays a theoretical foundation for the internal mechanical process of anchor system in earthen sites.

Key words: anchorage system in earthen sites, soil-grout interface, push-out test, shear strength, shear stress-displacement curves