# Numerical simulation of crack propagation and AE precursor characteristics in coal failure under confining pressures

## TL;DR

This study uses simulations to understand how cracks and sound signals develop in coal under pressure, helping predict dangerous coal bursts in deep mining.

## Contribution

The study introduces a novel framework linking crack propagation patterns and AE signals under triaxial stress to improve coal burst prediction.

## Key findings

- Peak strength increases with loading rate under low confining pressures but becomes less sensitive at higher pressures.
- Volumetric strain-stress curves help identify crack initiation and damage thresholds that shift with pressure.
- The b-value of AE signals shows a 'sharp-drop-plateau' pattern before coal failure.

## Abstract

Predicting coal bursts in deep mining requires understanding the crack propagation and acoustic emission (AE) characteristics of coal under triaxial stress conditions. This study employs discrete element simulation to investigate the mechanical behavior and AE responses of cylindrical coal specimens under varying confining pressures. The results demonstrate that peak strength increases with loading rate, particularly under low confining pressures, while higher pressures dampen this sensitivity. Volumetric strain-stress curves effectively identify crack initiation and damage thresholds, which increase with confining pressure while reducing the duration of unstable crack propagation. The proportion of tensile cracks gradually decreases while the proportions of shear and mixed-mode cracks increase. Specimens remain stable when βt-value < 1 and enter instability when βt-value > 1, with βt-value remaining unaffected by confining pressure variations., Meanwhile, b-value exhibit a “sharp-drop-plateau” pattern prior to failure. These findings provide a theoretical framework for interpreting AE signals in deep mining environments, enhancing coal burst prediction capabilities through mechanistic insights into confining pressure effects on crack evolution and precursor indicator.