Stress path effect and loading failure mechanism of surrounding rock in steeply dipping pitching oblique stope

Abstract

Discovering and revealing the stress path effect and load failure mechanism of surrounding rock in steeply dipping pitching oblique stope is the basis for realizing safe and efficient mining of such coal seams. Based on the study of the evolution law of roof caving and filling in pitching oblique stope, the three-dimensional physical simulation experiment, numerical calculation, theoretical analysis and field monitoring are used to reveal the load and instability mechanism of roof rock mass structure in different areas under the non-equilibrium constraint of gangue, and the temporal and spatial evolution law of overburden mining stress in different positions along the strike and tendency of working face is deeply analyzed. The results show that there are obvious regional characteristics of roof fracture and migration in steeply dipping pitching oblique stope. The lower fracture lags behind the middle and upper parts, and the effective support area of filling gangue is about 2 / 5 of the length of working face. The basic roof stress evolves from wedge to inverted trapezoid. The roof strata are damaged by tension and compression in the middle and upper regions, and by compression in the lower region. With the advancement of the working face, the magnitude and direction of the three-dimensional mining stress of the overlying rock have changed significantly. The asymmetric deflection transfer of the stress path leads to the failure and instability of the rock layer inside the bearing arch, and the bearing arch increases first and then tends to be stable. The peak abutment pressure of surrounding rock has a cumulative effect. The stress concentration in the lower area has a lag. The peak abutment pressure in the upper area is smaller than that in the true inclined working face, and the stability of the roof is enhanced. The peak values of the bending moment in the upper, middle and lower regions of the inclination are 483.71, 306.95 and 230.26 KN·m, respectively, and the peak values are located at 2–3 m in front of the coal wall. The relationship between the ‘support-surrounding rock’ of the stope presents significant regional characteristics. The research results have important guiding significance for the stability control of surrounding rock and safe and efficient mining of scarce high-quality coal seams such as steeply dipping coal seams.

Keywords

steeply dipping coal seam / pitching oblique stope / gangue sliding filling / stress path / fracture instability

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