Back-analysis approach for the determination of hydraulic conductivity in rock caverns

Abstract

Water seepage related problem is often the major geological hazard in underground rock excavation. In order to reduce the risk associated with extensive seepage, a reliable hydro-geological model should be established based on the in-situ investigation data. One of the challenges for establishing a reliable hydro-geological model is on how to determine the hydraulic conductivities of the fractured rock masses using the limited in-situ investigation data. In this study, a back-analysis approach for the determination of the hydraulic conductivities along a rock cavern is presented. To take the advantages of both the analytical solutions and the numerical methods, this paper proposed a semi-analytical approach for prediction of the water inflow into caverns with the horseshoe section, and the semi-analytical solution is used for the back-analysis of the hydraulic conductivity around a rock cavern based on the in-situ monitoring data. The hydraulic conductivities are obtained by using the EXCEL spreadsheet’s build-in optimization routine SOLVER to minimize the error function. The computed water inflow into the cavern is compared with the in-situ measured data. The results indicate that the derived hydraulic conductivity is acceptable.