Buckling failure of highly-stressed hard rocks surrounding deep underground openings and confining effects of backfilling material

Abstract

The buckling failure of highly-stressed hard rocks surrounding deep underground openings is analyzed in this paper. The effects of the eccentricity of maximum tangential stress and the radial stress gradient are considered in the analysis. The maximum lateral displacement and the maximum moment on the rock slabs are calculated by using vector superposition method. It shows that the slenderness, the eccentricity, the elastic modulus of the slabs and the loading stress play important roles on the buckling failure of rock slabs. The confining pressure provided by filling material can prove adequate to control buckling failure under certain loading conditions. The way to obtain the basic parameters in buckling analysis is also discussed in the paper. According to the buckling theory, a case study was discussed at the Maluping Mine in the Guizhou Kailin Group, China. By measuring the in-situ stresses, it was found that the maximum principal stress is as high as 35MPa at the Level +700m and buckling failure occurred in the surrounding rock masses. By experimental studies on the uniaxial compressive strength of the phosphorus gypsum cemented with Portland cement and fly ash, the required strength and the economic composition of backfilling material was determined. It was found that the confining pressure with 1.5-2.1MPa provided by filling material is sufficient to stop buckling and slabbing failure in the surrounding rock masses. It can realize the stability of the highly-stressed underground stopes. © 2012 Taylor & Francis Group, London.