Field and Numerical Investigation of High Wall Stability with Thin, Steeply Dipping Strata in an Underground Powerhouse

Abstract

This paper reports a case of a large-scale underground powerhouse whose high wall faces a significant stability problem owing to the presence of thin-layered, steeply dipping strata. The local failures are widely distributed cracks and remarkable rock mass displacement, which are determined as the combined effect of strata, natural stress, and significant excavation unloading. The 3DEC code based on distinct element method (DEM) is adopted and a new constitutive model suitable for modeling layered rock masses is proposed. The calculation results show that the 3DEC code, together with the proposed constitutive model, can provide satisfactory solutions for modeling the behavior of thin-layered and steeply dipping strata, thus assisting engineers with decision-making. To guarantee the wall stability, adjustments on excavation and rock support measures are both proposed based on numerical simulation results. It is considered that the excavation plan should be optimized, and some extra anchor cables are necessary for the high wall. Subsequent displacement monitoring data validate the efficacy of these newly added cables. Finally, the high wall keeps in stable condition at the completion of the powerhouse excavation. In general, it is hoped that this study presents a numerical evaluation method and also a reference for those seeking to address high wall stability in the presence of thin-layered, steeply dipping strata.