Determination of geological and geotechnical parameters of rock mass along penstock tunnels of Rudbar-Lorestan dam

Behnam Abrah¹, Lohrasb Faramarzi¹, Morteza Gharouni Nik^*2

¹ Department of Mining Engineering, Isfahan University of Technology

² School of Railway Engineering, Iran University of Science &Technology

Abstract

Accurate determination of geotechnical and geological parameters of rock mass was performed using geotechnical exploration results including, the laboratory and in situ tests, empirical relations, geological surveys and field observations. The rock masses along penstock tunnels of Rudbar-Lorestan have a complex geology and consist of Dalan, Hormoz and Mila formations, mostly composed of shale, marl, marly limestone to limestone and dolomite. In this study, based on the measured data, the rock masses along penstock tunnels were classified by engineering classification systems of RMR, Q and GIS. And, a new relationship between RMR and Q for the studied area was presented. There were various empirical relations between RMR, Q and GIS, that were used for estimating geotechnical parameters. It must be noted that each of the empirical relations found may produce proper results for special regions. In this paper, the deformation modulus, cohesion and friction angle of Dalan formation were evaluated using the results of in situ dilatometer tests, laboratory tests, and findings of more than 25 geotechnical exploration boreholes in Dalan formation. Afterwards, by calibrating the empirical equations through the measured data, the geotechnical parameters of Mila and Hormuz formations were accurately estimated.

Keywords: Rock mass, In-situ and laboratory tests, Geological and geotechanical parameters, Empirical relations, Penstock tunnels, Dilatometer