Geological Strength Index (GSI) and its application in Hungary

Abstract

In engineering geology the rock mass characterization can be performed by using various methods of which the
Geological Strength Index (GSI) is one of the recently introduced techniques. By applying the GSI method, design
parameters — such as angle of friction, modulus of elasticity, cohesion and compressive strength — can be evaluated and
calculated. The method was first developed for solid and blocky rock masses, but later it was extended to describe
heterogeneous rock masses such as flysch. The present paper describes the development of the GSI method and it
provides information about its applicability in Hungary for rock faces, tunnels and deep excavation sites. An Eocene marl
belonging to the Buda Marl Formation is the example based on which the methodology is based and subsequently
described. It is a heterogeneous rock mass with hard, strongly cemented calcareous marls and soft clayey sections
possessing soil-like characteristics. The case studies presented here include field and laboratory test results of projects
finalized at the Department of Construction Materials and Engineering Geology of the Budapest University of
Technology and Economics.