Experimental Investigation to Fabricate Synthetic Laminated Rock with Different Bedding Plane Cohesive Strengths

Abstract

Bedding plane properties influence the failure behavior of laminated rocks such as slate and shale. For safe and stable underground coal mine design it is imperative to understand the relationship between the bedding plane strength and the failure of laminated rock. However, it is difficult to obtain in situ laminated rocks with various bedding plane properties while keeping other properties constant. In the present research, we experimentally investigated various approaches to vary the weak plane cohesive strength (Cp). Concrete block incorporating a weak plane was casted and the Cp of the weak plane was varied experimentally using two methods. Direct shear tests along the planes validated that applying normal stress on the concrete block successfully varied the Cp. The verified method was then used to cast synthetic laminated rock (SLR) with various Cp. We then conducted Brazilian splitting tests on SLR with different orientations of bedding planes and compared the failure strength and failure modes with that of shale specimen. The results validated the second method as both failure strength and failure modes of SLR specimens matched the behavior of shale specimens. This research provided a validated method to fabricate SLR with different Cp in the laboratory.