Calculation method and influencing factors of uplift bearing capacity of rock-socketed pedestal pile

With the rapid development of transmission line engineering in the west of China, the uplift problem of the tower foundation affected by extreme weather has provoked increasing concerns. Based on Balla rupture surface assumption and limit equilibrium method, a simplified calculation method of uplift bearing capacity of rock-socketed pedestal pile is derived. According to the results of the centrifugal model test and in situ field test, it is verified that the Balla rupture surface hypothesis is suitable for describing the failure mode of rock and the reliability of the calculation method. Furthermore, by combing the PLAXIS 3D numerical simulation results, the influence factors of uplift bearing capacity are compared and analyzed. Results show that the failure mode of rock is a trumpet-shaped surface, and it can be expressed by Balla rupture surface equation. The undetermined parameter N of rupture surface shape presents a negative correlation with mechanical integrity and uniaxial compressive strength (UCS) of the rock. The complete soft rock (5 MPa < UCS ≤ 6 MPa) should be N = 0.6, the strongly weathered soft rock (5 MPa < UCS ≤ 6 MPa) should be N = 1.5, and strongly weathered extremely soft rock (UCS = 2.6 MPa) should be N = 3.0. Additionally, the method provides a good reference for the calculation of uplift bearing capacity of tower foundation in similar regions.