Analysis of the impact of rating methods for assessing the rock mass on its physical and mechanical characteristics and on the calculation of the support of a vertical shaft
Authors:   Saint Petersburg Mining University, DEMENKOV Petr Alekseevich 
Published: March 2023

The purpose of the work is to review the existing techniques for evaluating the stability of rock around the vertical shaft and to make the comparative analysis of the effect of using different rating techniques on the assessment of the strength and stability of the massif, as well as on the results of stress calculation on the inner contour of the lining. The relevance of the work. The forecasting of the development of deformations of the vertical shaft rock contour during mining operations is an important element of geomechanics. Its reliability depends on the correctness of determining the mechanical characteristics of the rock mass. For this purpose, it is necessary, by means of application of one of existing methods of massif evaluation, to pass from characteristics of tested core samples to the characteristics of the massif. Due to the need for the mineral’s extraction, vertical shafts and other underground structures are vital, therefore, the relevance of identifying the strengths or limitations of existing techniques for assessing the stability of the host rock massif should not be underestimated. The research’s methods. This work is a theoretical study, during which logical, analytical methods of scientific knowledge, quantitative and qualitative statistical analysis and synthesis of data, methods of mathematization and functional analysis were used. Based on the data of the borehole drilling, the transition was made from the physical and mechanical characteristics of the sample to the physical and mechanical characteristics of the massif, using different rating methods of rock evaluation, after which the deformation modulus of the massif and the stress on the contour of the mount were determined, and a comparative analysis of the results was carried out. The results of the work and its area of application. The paper gives a review of rating systems of rock massif structural disturbance estimation, presents some analytical methods of stability determination, reviews evaluation methods using field instruments and numerical simulation. Studies of the influence of different massif rating systems on determining the deformation modulus of the massif and the stresses in the lining on the example of five boreholes in two different fields in tectonically complicated mining and geological conditions are presented. According to the results of the study, the following dependences were established: with the same initial physical and mechanical properties of the sample, after switching to the characteristics of the array using the GSI index, the deformation modulus of the array is significantly higher than when using the RMR rating; when calculating the stresses on the fastener contour using the GSI index, the stresses on the inner fastener contour are significantly lower than when calculating using the RMR rating. The field of application of these results is the science of geomechanics as well as the industrial underground construction industry. Conclusions. When calculating rock modulus and stresses on the lining contour, methods of evaluating the stability of the massif significantly affect the results of the calculations. The assessment of the massif using only rating systems is not reliable; such an engineering problem requires the use of more than two rating systems for a more accurate assessment, as well as the additional use of approaches, in particular, mathematical modeling.