The composite bolt containing steel bar is applied successfully to the anchorage of earthen sites. However

its anchoring mechanism is only initially studied. In the Jiaohe ruins

a typical earthen site

the composite anchor containing steel bar (? 22 mm) were chosen to carry out the pull-out experiment as well as the interface strain monitoring among the bolt. The experimental results indicate that the maximum anchoring force of the 3 m-length bolt is over 190 kN; and the bolt shows the strong plastic deformation. The interface strain monitoring result reveals that as the damage interface the axial strain of the interface between steel and composite material is greater than the other ones. Due to the heterogeneity of the bolt

the irregularity of the axial strain occurs in the interface between bamboo and composite materials

which results in some local compression phenomenon. Meanwhile

the change of shear strain along bamboo-grout interface coincides with that of the pull-out load; and shear strain is transferred to the end of the bolt under larger load. Furthermore

because of the multilayer structure of the bolt

the transverse transfer and shearing expansion distinctly appear during pull-out experiment. The research lays the foundation to optimize the bolt structure and its anchoring craft.