Relationship between the fractal dimension and the rock mass classification parameters in the bátaapáti radioactive waste repository

Abstract

A fractured rock mass is divided by the fracture sets into mixed shapes of blocks and wedges. The geotechnical parameters of the rock mass are obviously dominated by the presence and the spatial distribution of fracture sets. In rock engineering, the determination of geotechnical parameters of rock masses is a key issue for the prediction of expected behaviour of the fractured rock mass. Several measurements and empirical methods can be used to investigate the characteristics of the fractures including its spacing and orientation. The goal of this paper is to find the possible connection between the calculated fractal dimension (D) and the derived values originating from several rock mass classification systems (e.g. RQD, RMR, Q, GSI). Principally, the derivation of fractal dimensions and the rock mass classification systems are based on empirical methods. For our present investigation the fractures visible in scores of pictures taken by automatic photo robot of the tunnel faces were used at the low and intermediate radioactive waste repository located at the Bátaapáti site in Southern Hungary. The BENOIT software was used to calculate the single fractal dimension according to the boxdimension methodology and the rock mass classification values were evaluated with the JointMetriX3D (ShapeMetriX3D) software. Our results show that some connection between geotechnical parameters and fractal dimension values can be obtained by the applied methodology. Using these empirical relationships, it is possible to carry out more safety construction and calculations in the radioactive waste repository in Bátaapáti.