Abstract

The coal seam strength and the failure criteria that represents the behavior of the coal seam are very important for mine section and pillar design. In addition, the same to roof and floor layers, which will form the roof-pillar-floor system. Therefore, the rock mass characterization is the most important job and it is the beginning of the underground ground control design. Another issue is the distribution or behavior of the coal seam strength for the whole mine area. Sometime, the coal seam strength assumed the same for entire area, but it is not true because the coal seam is heterogenic and anisotropic, and also the coal strength gets some effects due to faults and spacing between fractures. This paper has the objective to demonstrate the use of themethodology for geomechanics characterization to determine the strength for the Bonito coal seam and discuss the coal seam strength distribution around the entire mine area. The intact coal strength considered the laboratory tests that were proceeded during the lasts 17 years, including triaxial and uniaxial strength tests. It was note that there is a strong correlation between all laboratory strength tests with 90% of interval confidence. The explanation for this coal seam strength variation is the presence of the discontinuities and their variation in quantity and quality at each location in the mine area because the coal seam rock classification and its behavior will be affected by the quantity and quality of fractures.

Keywords: Coal strength;Rock mass classification;Failure criteria