Informatics Publishing Limited

Muhammad Tahir ¹, Noor Mohammad ¹

Affiliations
1 Department of Mining Engineering, University of Engineering & Technology, Peshawar, PK

Abstract

The deformation modulus of rock mass can either be measured using in-situ field tests or estimated empirically. However, the empirical method is an attractive and open choice for researchers to estimate the deformation modulus of rock mass economically, efficiently and accurately and many researchers have proposed empirical equations for estimation the deformation modulus of rock mass based rock mass classification systems. In this paper attempt has been made to collect and review some these published empirical equations developed so far based on Rock Mass Rating, Geological Strength Index, and Q rock mass classification systems. These empirical equations based on each classification system are grouped on the based on similar parameters. All the equations within certain group for all groups were plotted to obtain a viable range for which the equation is assumed to be reliable. An artificial data is generated for each group separately to from valid data points of existing equations. Keeping in view the trend of data points in the scatter plot of individual group, Gaussian and Sigmoidal type mathematical functions are fitted to obtain generalized equation for each group that consisted two or more than two valid equations. The new equations fitted to the data are optimized by minimizing residuals using Microsoft Excel built in Add-in “Solver”. It is observed that equations using sigmoidal function predict more precisely than equations using Gaussian function.

Keywords

Deformation Modulus, Rockmass, Estimation Methods, Empirical, Gaussian, Sigmoidal.

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Wahid Ali ¹, Noor Mohammad ¹, Mohammad Tahir ¹

Affiliations
1 Department of Mining Engineering, University of Engineering & Technology, Peshawar, PK

Abstract

This research work presents a case study of rock mass characterization on diversion tunnels at Diamer Basha Dam, Pakistan. Geological and geotechnical studies were performed to characterize the rock mass along the axis of diversion tunnel. The core specimens retrieved were tested in laboratory and physical and mechanical properties of the rock mass were determined. Detailed discontinuity survey was carried out to determine the type and orientation of discontinuities with respect to direction of tunnel drive. The rock mass was classified using Rock Mass Rating (RMR), Q-System and Geological Strength Index (GSI). Based on rock mass classification results, the rock mass along the tunnel alignment was divided into three Geotechnical units, where the combined effects of the engineering-geological conditions, the initial stress situation and the ground water conditions were predicted to present consistent tunneling conditions. It was concluded from the rock mass behaviour that conventional drill and blast excavation method can be used, assuming smooth blasting by skilled workers. Ground support system was proposed for the diversion tunnels using Q-System support chart. In order to facilitate the easy classification of the rock mass at the project site, new empirical relationships were developed between Q-system, RMR and GSI by using original field data statistically. The relationship between RMR and GSI was found to have a greater degree of confidence with a higher correlation coefficient (R²= 0.84).

Keywords

Characterization, Diversion Tunnel, Basha Dam, Geotechnical Units, Gabbronorite, Ultramafic.

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