Abstract: To obtain the optimal anchorage length for soilrock composite strata, indoor tests, numerical simulations, and engineering tests are conducted to investigate the working conditions for two types of anchorage lengths (12 m and 8 m). The results show the following: (1) The peak shear stress transfers from the beginning to the end of the anchorage section under the tension load, while the peak shear stress is low and the axial force decay rate is high in the anchorage in clayey soil gravel sandstone layer. (2) With the increase of tension load, the anchorage section in clayey soil gravel sandstone layer gradually transforms from tensile stress zone to compressive stress zone, the transfer rate of stress to the depth is low, and the anchorage solid has the characteristics of poor resistance to external load and high deformation. (3) The anchor cable axial force can be divided into three evolutionary stages: loss of prestress, rise, and fluctuation, and when the anchorage section passes through the clayey soilgravel sandstone layer, the prestress is lost in the fluctuation stage, and the prestress is nonuniformly distributed in different directions. (4) It is recommended to avoid anchoring in the soilgravel sandstone layer when the anchor cable passes through the soilrock composite strata.

Key words: soilrock composite strata, anchorage length, anchorage mechanism, pullout test, numerical simulation, field test