A Comparison of Underground Opening Support Design Methods in Jointed Rock Mass (TECHNICAL NOTE)

It is of great importance to consider long-term stability of rock mass around the openings of underground structure, during design, construction and operation of the said structures in rock. In this context, three methods namely, empirical, analytical and numerical have been applied to design and analyze the stability of underground infrastructure at the Siah Bisheh Pumping Storage Hydro-Electric Power Project (HEPP) in Iran. The geological and geotechnical data utilized in this article were selected and based on the preliminary studies of this project. In the initial stages of design, it was recommended that, two methods of rock mass classification Q and RMR should be utilized for the support system of the underground cavern. Next, based on the structural instability, the support system was adjusted by the analytical method. The performance of the recommended support system was reviewed by the comparison of the ground response curve and rock support interactions with surrounding rock mass, using FEST03 software. Moreover, for further assessment of the realistic rock mass behavior and support system, the numerical modeling was performed utilizing FEST03software. Finally both the analytical and numerical methods were compared, to obtain satisfactory results complimenting each other.