Mechanical behaviour and acoustic emission characteristics of the reinforced soft muddy rock under various moisture content levels

In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present, a series of confined compressive tests and Acoustic Emission (AE) recordings were conducted subject to various moisture content levels and lateral confining stresses. It was found that the failure modes of the reinforced rock specimen were affected by the moisture content level and the lateral stress σ₂ in a way that the load bearing capacity of the reinforced rock would increase with the lateral stress σ₂ but decrease as the moisture content increased. An increase in the moisture content would reduce the extent of the influence of the lateral stress on the load bearing capacity of the reinforced rock. In addition, much less AE counts were recorded when the moisture content increased indicating that the crack initiation and propagation in this case was easier due to the reduction of the required external input energy. With increasing moisture content, the failure mode of the specimen gradually changes from sudden and brittle to progressive and ductile. Moreover, the hydration reaction became more significant leading to a complete debonding between the grout and the rock. Consequently, the reinforcement provided by the rock bolt to the rock became negligible.