Document Type : Original Article
Authors
1
Department of Mining Engineering, Faculty of Engineering, University of Kashan, Kashan, Iran
2
Department of Mining Engineering, Faculty of Engineering, Urmia University, Urmia, Iran
10.22077/jgm.2025.8164.1032
Abstract
Geological discontinuities can either be infilled or unfilled, with the infilled type being the most common. Various materials with different compositions and strengths can fill these discontinuities. Previous studies have used plaster, sand, and clay mixtures to model infill materials. This study prepared three infill materials with uniaxial compressive strengths (UCS) of 0.616, 2.203, and 3.920 MPa by mixing plaster, sand, and clay with water in different weight ratios. A total of 180 triaxial compressive strength tests were conducted to evaluate the impact of these materials on the axial strength of specimens with discontinuities oriented at angles of 30°, 45°, 60°, and 90°. These tests were performed under confining pressures (CP) ranging from 0 to 20 MPa. Observations revealed a failure in intact rock fragments for discontinuities oriented at 0 and 90°. Axial strength significantly decreased, showing reductions of about 22%, 33%, and 67% for UCS values of 3.920, 2.203, and 0.616 MPa, respectively, when comparing 90° to 30° orientations. Indeed, the failure occurred within the lower-strength infill material, while for the more robust infill material, it happened on the interface of the discontinuity and the infill material. With increasing the CP, no significant change was seen in the decreasing trend of the axial strength with increasing the orientation angle in the range of 30° to 90°. The type of infill materials did not impose any significant effect on the axial strength at lower CPs. At higher CPs, however, the axial strength was seen to increase with increasing either of the uniaxial strength, internal friction angle, and sand content of the infill material. In all tests, the obtained axial strength was lower than that predicted by the Jaeger theory.
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