Experimental，theoretical and computational analysis on splitting failure mechanism of high sidewall caverns

The splitting failure of high sidewall caverns has become an important factor affecting the construction and excavation safety of the underground powerhouse of large hydropower stations. In order to clarify the formation mechanism of this phenomenon，taking the high sidewall cavern of the main powerhouse of Pubugou Hydropower Station as a case study，the true 3D geomechanical model test of excavation and unloading of high sidewall cavern under high in-suit stress is carried out，and the nonlinear deformation characteristics and splitting failure law of excavation and unloading of high sidewall cavern are revealed. On the basis of the model test，an elastic-plastic damage-softening model of splitting failure of underground cavern based on strain gradient and the failure criterion of splitting failure are established. Based on this，the calculation and analysis program of underground cavern splitting failure is developed based on ABAQUS software. Through the numerical simulation of multiple working conditions，the generation conditions and formation mechanism of splitting failure of high sidewall cavern are effectively revealed：the important condition of splitting failure is that the initial maximum principal stress is parallel to the direction of tunnel axis and the value reaches a certain degree. In the process of excavation and unloading，the oscillating change of the stress of the high sidewall is the fundamental mechanical cause of splitting failure. The research results provide an important experimental and theoretical basis for the prevention and control of splitting failure of high sidewall caverns. © 2023 Academia Sinica. All rights reserved.