Applications and Limitations of Geotechnical Classification Systems

Abstract

During the feasibility and preliminary design stages of a project, when not enoughdetailed information on the rock mass and its stress and hydrologic characteristics is available,the use of a rock mass classification scheme can be of considerable benefit. This can be usedas a check-list to ensure that all relevant information has been considered. It is possible thatone or more rock mass classification schemes can be used to build up a picture of the composition and characteristics of a rock mass to provide initial estimates of support requirements, and to provide estimates of the strength and deformation properties of the rockmass.Different classification systems place different emphases on the various parameters,that's why in our tunnel project we use 3 methods RMi, Q, RMR and compares the results.One of the results of the comprehensive field work to clarify the geological conditions for the tunnelling works was a comprehensive data collection of rock and rockmass descriptions that contains information about lithology, petrology, mineralogy, texture, fabricand on-site evaluated rock and rockmass physical and mechanical properties. For further dataprocessing the above mentioned rock- and rockmass-classifications were used to give comparable assessments for tunnelling conditions and lining requirements.The paper at hand is an attempt to clarify, which systems of rockmass classification arebest-fit to describe the rockmass conditions of the project area. Which were the limitations of each system used and how to improve their applications. The result is displayed in the geological longitudinal sections of the headrace Moglice - Graboves (Devoll Project,Albania). Consequently the paper at hand is an integrated part of the engineering geological contribution in the feasibility report for the client DHP in which GSI and little "q" systems were used as well.