Investigating the mechanism of splitting failure in deep high sidewall cavern based on complex function and strain gradient

Abstract

Owing to excavation-induced unloading, high sidewalls of underground powerhouse are often subjected to splitting failure, which produces many adverse effects to the construction of the cavern. To reveal the formation mechanism of splitting failure, we proposed a novel elastic–plastic damage softening model based on the strain gradient theory and the elastic–plastic damage theory. Using the ODE45 program in MATLAB, the numerical solution of the displacement and stress of circular cavern was solved based on the newly proposed elastoplastic damage model. We then adopted the complex function method and used the Schwarz-Christoffel integral formula to obtain the mapping function from the outer domain of high sidewall cavern to the outer domain of the unit circle. Finally, the elastic–plastic region and the displacement distribution of high sidewall cavern were obtained by mapping the obtained elastic–plastic solution of the circular cavern under the axisymmetric condition. The numerical analysis results were consistent with the previous geomechanical model test results. The results presented that the stress of high sidewall of an underground powerhouse exhibits an oscillating variation with alternating peaks and troughs, which is the mechanical mechanism of splitting failure.