ABSTRACT
Engineers have excavated rocks for mining and tunnel purposes for hundreds of years. Unfortunately, there have been several occasions where a section or the whole tunnel collapsed in weak or heavily weathered rocks. To avoid failure, engineers have developed rock mass classification schemes so that appropriate support measures can be readily determined and implemented. Rock mass rating (RMR) has been modified to include the in situ and induced stresses, stress changes and the effects of blasting and weathering, resulting in the modified RMR. The objective was to characterize the rock mass and determine the tunnel support requirements. Geological strength index was introduced by E. Hoek to estimate the reduction in rock mass strength for different geological conditions. The generalized Hoek- E. T. Brown criterion can be used to estimate the strength characteristics of rock mass, which is essential in the assessment of rock mass stability.
