Relations Between Geologic Strength Index, Discontinuities and Point Load Strength Index of Some Rocks in Kemi Mine

ABSTRACT: In rock engineering practice, Geological Strength Index (GSI) is a well-accepted method for rock mass classification with cross cutting applications. For instance, during blast design and support prediction in tunneling, stope and foundation planning and development. However, the forementioned method involves interpreting geological structures, which are somewhat cumbersome for engineers with limited knowledge on geology. In this study, relations between GSI, intact rock strength (denoted by point load index Is50) and rock mass structure (denoted by the ratio of rock quality designation RQD and joint number Jn) was investigated. To achieve this, a total of 1033 measurements of forementioned parameters were collected from rocks in Outokumpu Kemi mine. Measured data were segmented into training, testing and validation sets for empirical and artificial neural network (ANN) models. Results from reliability evaluations revealed good relations exist amongst GSI, intact rock strength and rock mass structure. However, the ANN model slightly outperformed the best empirical model for predicting GSI. Following ease and timeliness in measuring input parameters (Is50, RQD and Jn), models developed in this study can be applied in estimating GSI during time constrained engineering projects by personnel with limited knowledge of geology.