Abstract:

Currently, the bearing capacity design of prestressed steel anchor pipe-anchor cable composite structures often neglects the mechanical properties of the four constituent materials—cable, grout, steel pipe, and surrounding rock—as well as the interfacial behaviors among them, thereby resulting in theoretical research lagging behind engineering practice. To elucidate the effects of various parameters on the bearing capacity and failure mechanisms of these composite structures, four full-scale experimental tests were conducted, supplemented by numerical simulations. The analyses focused on key parameters including bearing capacity, failure modes, and strain distribution at different interfaces. The results indicate that: 1) The bearing capacity and strain of the composite structure are predominantly governed by the number of steel strands, while the influence of steel pipe diameter is comparatively minor. Within the tested range, adding one steel strand increases the bearing capacity of the steel anchor pipe-cable composite structure by an average of 276 kN. 2) With an increasing number of steel strands, the failure mode transitions from local strand rupture to simultaneous rupture of multiple strands, with no other failure modes observed, indicating that the interface bond strengths all surpass the ultimate tensile strength of the steel strands. 3) The strain distribution patterns at the interfaces between the steel pipe and grout, as well as between the grout and surrounding rock, generally demonstrate structural consistency; however, the latter exhibits a discernible "lag" phenomenon in comparison to the former. 4) Increase in the grout’s elastic modulus, anchorage length, and steel pipe diameter can all effectively reduce the deformation of the corresponding materials.

Key words: steel pipe anchor cable, full-scale test, bearing capacity, failure mode