Abstract: The bearing mechanism of the composite foundation of excavation and rock bolt was unclear. In view of this, an analytical model of the uplift bearing capacity of the composite foundation was established using Plaxis3D based on field test conditions to probe into the uplift bearing mechanism of the composite foundation foundation. The influences of soil elastic modulus, rock elastic modulus, and soil cohesion on the bearing capacity of each part of the composite foundation were examined. The bearing capacity, uplift deformation, and plastic zone development of excavation foundation and rock bolt were analyzed. The improved design of the composite foundation was also given. Results demonstrate that the rock bolt with large deformation stiffness controls the ultimate state of uplift bearing of the composite foundation; the deformation compatibility between excavation foundation and rock bolt is the key to the bearing capacity of the composite foundation. Increasing the depth of the excavation foundation embedded in rock can effectively improve the pull-out bearing capacity of the composite foundation.

Key words: composite foundation, excavation foundation, rock bolt foundation, uplift bearing capacity, numerical analysis, deformation compatibility