Combining geomechanical and hydrogeological modeling for drainage analysis in Block Caving mine development

Abstract

Underground caving operations are naturally affected by mud and water inflows. These inflows occur mainly because caving operations are connected to a surface or a previous mining area through a broken subsidence zone where there is potential to accumulate water. Additionally, the surface/groundwater can mix with fine fragments within the broken column, which can generate a sudden mud rush through the drawpoints. A key mitigation measure for this hazard is drainage of the surrounding rock mass. However, an effective mine drainage system can be designed only if the physical behavior of groundwater flow is known. This work proposes a methodology that couples a geomechanical model designed in FLAC3D© with a hydrogeological model developed in FEFLOW©. The geomechanical model determines the spatial and temporal distribution of the stress field and induced strain due to caving. The spatial and temporal distribution of the hydraulic conductivity is analytically defined as a function of the induced strains. Then, the hydrogeological model is linked with the geomechanical model to simulate patterns of groundwater flow through the rock mass during cave propagation. Finally, a drainage chart is presented based on the hydrogeological simulation considering different caving stages and different system recharge due to surface inflows.