Inversion of the 3D in situ stress field in a complex valley area around the underground cavern group of the Yingliangbao Hydropower Station

Abstract

The inversion of three-dimensional in situ stress fields in complex river valleys is of great significance for evaluating the excavation stability of deep underground caverns. Based on known in situ stress measurements, it is a major method for obtaining the geostress of the engineering area through the inversion geostress of the whole area with the application of geo-mathematical mechanics. However, the inversion results are often limited by the geological structure and heterogeneous alterated rock, as well as the measurement data reliability. A three-dimensional nonlinear neural network inversion was combined with a simulation of stratigraphic denudation by stages, tectonic compression, and alteration degree in the fault structure. The model was then applied to an underground cavern group of the Yingliangbao Hydropower Station. Comparative analysis showed that the inversion results were in reasonable accordance with the measured in situ stress values. Moreover, the reliability of the three-dimensional in situ stress field obtained using this method was further verified from the stress-induced failure during the cavern excavation. This technique is helpful for optimizing the design of subsequent excavation and reduces the potential instability of surrounding rock during a layered excavation.