Estimation of concrete lining thickness for stability of circular mine shafts in different rock masses

Abstract

In this study, in each of the nine-meter-diameter shafts which has different depths (100, 300, 500, 700 and 900 meters), the M-RMR values were considered as 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 respectively. In addition, it was assumed that the uniaxial compressive strength (?ci) was 50 MPa and also was D = 0 and D = 0.5 for situation formed in surrounding rocks based on blasting. The under condition, the numerical analyses were made by Phase2 software. As a result, in this parametric study, a total of 100 scenarios were analysis. The optimum thickness (tc, m) of concrete support with C20 class concrete have been identified for each scenario. The maximum principal stresses (?1, MPa), total displacement (U, mm), the number of yielded elements formed in the surrounding rocks, strength factor (SF) and thickness of yielded region (ht,, m) respectively were determined. Using Phase2 software 10 integrated charts were prepared. if the rock mass classification value (M-RMR) is known, the thickness of yielded surrounding rocks (ht, m), concrete support thickness (tc, m), the total displacement (U, mm) to be occur in the shaft can be determined by the integrated charts. Also, for (M-RMR) vs ht (m) and (M-RMR) vs U (mm) behaviors expressed in the integrated charts, two mathematical models were developed using SPSS software. © 2020 ISRM.