# Stress Deflection Effect and Rockburst Mechanism in Staggered Roadways Beneath “L-Shaped” Residual Pillar

## TL;DR

The paper explains how residual coal pillars create high-stress zones that cause rockbursts in staggered roadways and introduces methods to prevent them.

## Contribution

A novel method for correcting rockburst hypocenter depth using moment tensor analysis and a prevention system for rockbursts in coal mines.

## Key findings

- Compressive-shear failure of coal pillars is the dominant rupture mode in rockburst events.
- The 'L-shaped' coal pillar structure's stress deflection effect increases rockburst risk.
- A prevention system reduced rockburst frequency to zero in field tests.

## Abstract

What are the main findings?
We proposed a novel method for correcting the vertical height of rockburst hypocenters based on the moment tensor force mechanism.The predominant type of source rupture under the influence of residual coal pillars is compressive fracturing.

We proposed a novel method for correcting the vertical height of rockburst hypocenters based on the moment tensor force mechanism.

The predominant type of source rupture under the influence of residual coal pillars is compressive fracturing.

What are the implications of the main findings?
The “L-shaped” high-stress structure formed by residual coal pillars and its stress deflection effect are the primary causes of rockbursts.

The “L-shaped” high-stress structure formed by residual coal pillars and its stress deflection effect are the primary causes of rockbursts.

Frequent rockbursts in staggered roadways beneath residual coal pillars pose a critical challenge for the slice mining of ultra-thick coal seams. Taking the LW250101-2 of Huating Coal Mine as a case study, this paper systematically reveals the stress evolution laws and rockburst mechanism induced by irregular residual pillars by integrating microseismic (MS) monitoring, moment tensor inversion, and numerical simulation. First, source mechanism inversion analysis elucidated that compressive-shear failure of coal pillars was the dominant rupture mode in five of the eight recorded rockburst events. Second, numerical simulations demonstrate that the width of the left wing and the thickness of the right wing of the “L-shaped” coal pillar structure are the key geometric factors controlling rockburst risk; larger dimensions correlate with more intense stress concentration and higher-energy MS events. Moreover, the stress deflection effect of “L-shaped” coal pillars causes the haulage gateway of the LW250101-2 to remain in a state of stress accumulation, increasing its susceptibility to rockburst. Finally, a synergistic prevention system consisting of deep-hole roof blasting, large-charge coal blasting, and ultra-deep large-diameter boreholes was implemented. Field monitoring confirms that these measures dissipated high-stress concentrations, reduced rockburst frequency to zero and ensured safe mining.