Abstract

This study aims to present a statistical analysis by using the newest data of intact strength and elastic parameters for Kiruna and Malmberget rock masses and examining their correlation with geological and alteration characteristics. In recent years, extensive geotechnical programs have been conducted in Kiruna and Malmberget mines to identify intact rock strength and elastic parameters for various rock masses. On one hand, crucial rock mass classification systems such as IRMR, RMR89 or Q rely on subjective assessment of the intact rock strength (IRS), or objectively through point load tests. On the other hand, accurate measurements of intact rock strength and elastic parameters are essential for a realistic estimation of in situ geotechnical conditions and stresses in deep mine designs. Ongoing UCS and TCS campaigns in both mines have yielded valuable information, contributing significantly to geotechnical models. Based on geotechnical borehole logging, face mapping and geotechnical laboratory testing, it is well-established through the previous years that Kiruna rock masses exhibit greater strength compared to Malmberget. This study’s findings add to the geotechnical knowledge base to show the intact rock strength of Malmberget rock types ranges from 100 to 300 MPa. In some instances, unaltered granite and trachyandesites exhibit strengths surpassing 300 MPa, whereas biotite schist and massive magnetite may exhibit intact strength below 90 MPa. In Kiruna rock types, a different scenario unfolds, showcasing a variation in intact strength between 180 and 400 MPa, including massive magnetite. The unaltered, strongest rock types in Kiruna such as porphyritic andesite-trachyandesite even exceed 500 MPa.