# Compressive properties analysis of mono-sized fragmented coal and rock

## TL;DR

This study examines how fragmented coal and rock compress under stress, revealing insights into subsidence and mining strategies.

## Contribution

The study introduces a custom compaction apparatus and identifies three distinct compression phases in fragmented coal and rock.

## Key findings

- Fragmented coal and rock show progressive axial strain with decreasing porosity under stress.
- Acoustic emission activity increases proportionally with consolidation intensity.
- Coal produces higher acoustic emissions than rock during compression.

## Abstract

The compressive properties of fragmented coal and rock aggregates within goaf critically influences surface subsidence dynamics and reservoir development strategies. This study conducted constrained compression testing on mono-sized fragmented coal and rock particulate materials using a custom-designed compaction apparatus, evaluating parameters including compressive resistance, pre-/post-compaction mass variations, porosity evolution, and acoustic emission (AE) signatures. Experimental observations demonstrated progressive yet decelerating axial strain development under increasing stress, accompanied by diminishing porosity reduction rates. AE activity exhibited proportional escalation in both event frequency and energy release intensity during particle consolidation. Particle dimension inversely correlated with compaction strength, while fragmented coal generated higher AE responses compared to rock counterparts. Three distinct compression phases were identified: void compaction, pore compaction, and particle recombination. These findings establish mechanistic insights for optimizing goaf flow field modeling and backfill mining techniques through enhanced understanding of energy dissipation patterns in particulate media.