# The deformation characteristics and the prefabricated crack pressure relief stability control of a small coal pillar roadway under stress superposition

## TL;DR

This study explores how prefabricated cracks in coal pillars can reduce stress and improve stability during high-pressure coal mining.

## Contribution

A novel pressure-relief strategy using prefabricated roof cracks to control stability in high-stress small coal pillar mining.

## Key findings

- Prefabricated cracks increased the caving angle from 55° to 70.5° and reduced the roof cantilever length by 48%.
- The technique lowered vertical stress in coal pillars from 5.5 MPa to 2.5 MPa at 3 m depth.
- The method effectively mitigates energy density surges caused by dynamic pressure events.

## Abstract

The substantial pressure acting on small coal pillars poses a formidable challenge to maintaining stability during mining operations. Small coal pillar mining under high-stress conditions has thus emerged as one of the most critical bottlenecks in sustainable coal production. In this study, the deformation characteristics of a small coal pillar roadway under stress superposition were investigated via numerical simulation. Physical modeling was further employed to elucidate the impact of prefabricated roof crack on the migration behavior of overlying strata, alongside the development of a pressure-relief stability control strategy. The vertical stress on the small coal pillars was exacerbated by four dynamic pressure events, leading to a surge in energy density, and further exacerbating the energy levels of the small coal pillar. The prefabricated cracks effectively altered the strata caving characteristics and roof overhang structure, the caving angle increased from 55° to 70.5°, and the length of the roof cantilever structure was reduced by 48%. Field applications demonstrated that this prefabricated crack technique achieved remarkable pressure-relief effects, with the vertical stress increment at a depth of 3 m in coal pillar decreasing significantly from 5.5 MPa to 2.5 MPa. These findings provide a robust theoretical and technical foundation for the stability control of high-stress small coal pillar mining panel.