Comparison of different calculation methods of Geological Strength Index (GSI) in a specific underground construction site

摘要

The Hoek-Brown (H-B) empirical failure envelope is widely used for calculating the mechanical behavior of the rock mass. An important input parameter of the H-B failure envelope is the Geological Strength Index (GSI), which was developed for the description of rock structure and block surface conditions. Using the GSI, the mechanical behavior of the rock mass can be calculated easily and accurately for both very poor and very good rock mass qualities. Thus, knowing GSI value is an important input parameter for rock engineering calculations.There are several qualitative methods which determine the GSI value accurately but no general international standard has been specified yet. Our objective in this paper is to analyze the different published methods for the determination of the GSI based on observations during the construction phase of the Bátaapáti (Hungary) National Radioactive Waste Repository (NRWR). Examinations of the values determined on-site gave significantly different results. Various correlations were determined between the calculated GSI values. Regarding the different determination methods of the GSI, good correlation results were provided based on the rock mass classification data of tunnel construction phase.It was found that there is no corresponding method for the determination of the GSI value in all cases, the calculation of the GSI can be site-dependent. The applied rock mass classification process is recommendable for the further design and implementation works of the NRWR and as an appropriate reference to other underground projects.