Acoustic Emission Signature and Volumetric Strain for Identifying the Compaction–Dilatancy Regime of Purvanchal Himalayan Sandstone

Rocks subjected to a generalized state of stress exist in either the compaction or dilatancy regime. The compaction regime favours engineering applications as microcracks are compacted or closed, creating stable conditions. Conversely, the dilatancy regime is characterized by initiating and propagating unstable microcracks, leading to cumulative damage and unfavourable conditions for rock engineering (RE) structures. Therefore, identifying the compaction–dilatancy (CD) regime is crucial for the safe and reliable design of the RE structures. The transition between the compaction and dilatancy domains is governed by the microcrack initiation–propagation (MIP) process. Traditionally, the MIP process is assessed using the volumetric strain method (VSM). Recently, the non-conventional acoustic emission (AE) technique has been employed to identify it more accurately. This study employs the AE signature and volumetric strain as a rock engineering tool to determine the CD transition regime and stress. The current research is conducted on the Disang sandstone (DS) of the Purvanchal Himalayan range. The findings reveal that the CD transition stress was 46.8 MPa and 49.9 MPa using the VSM and AE-based methods, respectively. These results demonstrate that real-time AE monitoring can reliably estimate the CD transition stress in close agreement with conventional methods. The results underscore the immense potential of AE techniques for advancing the understanding of rock behaviour, positioning them as a promising technique in rock engineering.