Mechanical characteristics of rock in place in analytical calculations on rock pressure phenomena in workings

Abstract

ON ROCKIn the planning of main workings, the calculation of rock pressure manifestations in workings in an inhomogeneous stratified rock mass with fixed angles of dip (from flat-lying r steeply dipping) and with fixed angles between the axis of the working and the direction of the strike are of practical importance . The need to take account of the angle between the axis of the working and the direction of the strike leads to a threedimensional scheme of calculations. So far, the problem has not been solved over the whole of space with consideration of actual geometry and jointing of the rocks near the periphery of the working in time-dependent form by analytical or numerical methods. In planning work this problem is therefore solved by empirical methods; the data involve the strength of a rock fragment Rc and the depth of the working below the surface, which determines the stress state of the solid rock. The geological and mining conditions are taken into account by means of correction coefficients in the form of factors multiplying the calculated displacements and loads on the supports for typical conditions. This approach, which is based on a formal description of the results of field observations, which does not completely explain the mechanism of the phenomenon, and which takes no account of the variability in the rheology of rocks, is valid only in a limited range of conditions. To broaden this range and to improve the reliability of the predicted displacements and particularly of the load on the supports, it would be advantageous to make use of experimental-analytical methods. It would be rational to base them on analytical solutions for simple schemes of calculation (axial symmetry and homogeneous medium), but taking the fullest possible account of the theology and deformation properties of the medium; to correct the discrepancy between the assumed and actual schemes of calculation, it would be necessary to introduce empirical correction coefficients to the original data determining the state of stress and mechanical properties of the solid rock.Below we will discuss approaches to determination of the theoretical strengths and elastic and theological characteristics of the rocks, which can be used in analytical calculations on rock pressure phenomena in workings.Strength Characteristics. Analysis of the results of field tests on rock specimens of large size has established the relation between their strength and the number and direction of the system of fractures in relation to the direction of the greatest principal stress, the contact conditions at the fractures, the ratio of the dimensions of the specimens to those of the elementary rock blocks, and the relations between the elements of inhomogeneity in the specimens. The analogy between these relations and the above-mentioned features of the scheme of calculation resembling the real situation enables us to incorporate most of the correction coefficients into the calculated strength of the solid rock. Owing to the great difficulty of testing large rock...

Stress-strain state of rock mass around pillars and chambers considering the angle of occurrence of the ore body

“…In order to determine the influence of inclination angles of the ore body, the paired dependences were initially obtained. The allowable compressive and tensile stresses were chosen as a function (Amusin & Linkov, 1973). The following dependences of allowable stresses on the inclination angles were obtained, for tensile allowable stresses:…”

Modeling Spatial Variance and Investigating the Effects of Variability on Intact Rock Strength and Stability of Entries in a Longwall Mine

“…Researchers often use the deterministic approach in solving rock mechanics problems. Researchers can use single mean values of limited site data to estimate the intact rock parameters, such as the strength and deformation modulus [1,3,11]. However, the estimations are always questionable, as the deterministic methods ignore the inherent variation in the intact rock.…”