Numerical back analysis method of three-dimensional in situ stress fields considering complex surface topography and variable collinearity

Numerical back analysis based on incomplete in situ stress measurements is widely used to estimate the threedimensional (3D) in situ stress fields of large deep underground caverns. However, the variable collinearity caused by complex geological environments has rarely been considered. This paper proposes a numerical back analysis method for 3D in situ stress fields based on stepwise regression (BSSR). In BSSR, the collinearity between independent variables is associated with the surface topography, and insignificant variables caused by variable collinearity are eliminated through stepwise regression. BSSR was applied to the underground powerhouse of a hydropower station for validation, and the results showed that it can reliably estimate the 3D in situ stress field despite the complex geological environments. Multidimensional mathematical models of in situ stress fields were established with the improved predictive ability and clear physical meaning, which can quantify the contributions of six geological actions and three stress sources. The findings of this study can help with understanding the formation mechanism of in situ stress fields for large, deep underground caverns in complex geological environments and provide a useful reference for optimizing excavation schemes and support designs.

Automated summary

This paper proposes a numerical back analysis method for estimating the three-dimensional in situ stress fields of large deep underground caverns in complex geological environments. By utilizing stepwise regression, the collinearity between independent variables is associated with surface topography while eliminating insignificant variables caused by collinearity. The method was validated in an underground powerhouse of a hydropower station and showed reliable estimation of the 3D in situ stress field. It also established multidimensional mathematical models with improved predictive ability and clear physical meaning, quantifying the contributions of geological actions and stress sources.