Zhijun Wan

Experimental Study on Anisotropic Strength and Deformation Behavior of a Coal Measure Shale under Room Dried and Water Saturated Conditions

This paper presents an experimental investigation of anisotropic strength and deformation behavior of coal measure shale. The effect of two factors (i.e., anisotropy and water content) on shale strength and deformation behavior was studied. A series of uniaxial and triaxial compression tests were conducted on both room dried and water saturated samples for different lamination angles. The test results indicate that (1) the compressive strength, cohesion, internal friction angle, tangent Young’s modulus, and axial strain corresponding to the peak and residual strengths of room dried specimens exhibit anisotropic behavior that strongly depends on the orientation angle ; (2) in comparison to the room dried samples, the compressive strength and Young’s modulus as well as the anisotropy are all reduced for water saturated specimens; and (3) the failure mechanism of the samples can be summarized into two categories: sliding along lamination and shearing of rock material, with the type occurring in a particular situation depending strongly on the lamination orientation angles with respect to the major principal stress. According to the findings, it is strongly recommended that the effect of anisotropy and water content on the strength and deformation behavior of the rock must be considered in ground control designs.

UNA METODOLOGÍA INTEGRAL DE PROTECCIÓN PARA PREDECIR LOS RIESGOS DE APANTALLAMIENTO EN MINAS DE CARBÓN EN ESTADOS UNIDOS

ABSTRACT: Shield support hazard prediction is important for the safety and productivity of an underground coal mine. Hence, research should be conducted on shield support hazard prediction. Thus, this study presents a comprehensive methodology for predicting shield support hazards in a virgin mining area. A total of 33 surface boreholes were drilled to cover the general mining area. All analyses were based on the extensive strength and physical properties of strata above and below coal seam B, including coal seam B itself. The modified detached roof block model was used to determine support roof load capacity, and the roof load isopach maps for three mining heights were drawn to show the load distribution for different mining heights. A regression equation was used to obtain the maximum floor pressure, and the isopach map showed the value difference between rock mass strength and floor pressure distribution. To clarify the geological discontinuities and immediate roof type variation trend, a fence diagram was drawn, and the corresponding responses were discussed. By combining the roof load capacity, floor pressure, and geological discontinuities, shield support hazards were clearly illustrated by a hazard map. The proposed methodology can predict the potential shield support hazards and identify areas where supplementary support can be implemented, thereby enabling mining engineers to incorporate the roof load capacity, floor pressure, and geological discontinuities effectively into an integrated hazards prediction map for use in support design and supplementary support strategies.