Assessment of rating parameters of the rock mass conditions at Udachny underground mine deep levels

Geotechnical rating classification systems of rock masses are an important tool in the design of underground mining systems. They are especially relevant at the early stages of project development, when primary mining and geological information is available to a limited extent. The presented work shows an approach to the collection of initial information and calculation of RMR (Rock Mass Rating) and Q Index for the rock mass of deep levels of the Udachny underground mine exploiting the kimberlite pipe of the same name. Since the classifications are multi-component systems, they impose heavy demands on the scope and quality of primary data, which can be met by applying an integrated data collection system. The bulk of these were obtained by acoustic televiewer tool (ATV) combined with geologic and structural logging of non-oriented core. Data on physical and mechanical properties of rocks, stress-strain state, and hydrogeological conditions were also used. The ratings were calculated interval by interval along holes, in which acoustic logging was performed. The acoustic wave amplitude parameter, which depends on the physical properties of a rock mass and the degree of its structural disturbance, was proposed as one of the criteria for distinguishing geotechnical intervals. The moderate level of correspondence between Q and RMR systems was established to be due to the different “sensitivity” and structure of the input parameters. Using the calculated ratings, the rock masses of ore bodies and host sediments were evaluated for stability (classes/categories have been assigned), and the optimal method and parameters of workings support were determined. The geotechnical database accumulated during the research process provides the feasibility of calculating alternative ratings such as MRMR, RMi, GSI, etc., without the use of transient equations.