*Important notice: This news reports on an unedited version of an accepted paper and is awaiting final editing. Therefore, the paper should not be regarded as conclusive or treated as established information.
In Shandong Province, China, researchers have investigated rockburst risk in an irregular pillar intersected by multiple faults in a deep coal mine. Their findings, published in Scientific Reports, provide a framework to identify critical mining zones and develop targeted rockburst-prevention measures in deep mines.
Study: A risk analysis of irregular coal pillars subjected to impact from multiple fault cutting in deep mines. Image Credit: vilai12 seehalath/Shutterstock.com
Their framework combined field monitoring, theoretical analysis, numerical simulations, and microseismic observations to examine how mining advance, fault structures, and changes in coal-pillar width influence stress redistribution.
Addressing Rockburst Risk in Irregular Coal Pillars
Rockbursts pose a major safety challenge in deep coal mining because increasing mining depth and tectonic stress can cause substantial elastic energy to accumulate within coal pillars and surrounding strata.
This becomes more complex when faults intersect coal pillars, altering the normal transfer of mining-induced stresses. In sectional pillar areas, mining on both sides can generate lateral abutment pressure, while faults can act as barriers to stress transfer and concentrate stress in localized regions.
The researchers focused on the 1310 working face of a deep mine in Shandong Province, where the coal pillar between the 1306 and 1310 working faces has an irregular geometry and is intersected by multiple faults. The pillar width changes from 158 m to 106 m along the mining direction, creating different stress conditions as the working face advances.
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The study addresses several limitations in existing research, particularly the limited understanding of how multiple faults and abrupt changes in pillar width jointly influence stress redistribution and rockburst risk.
The researchers therefore combine a theoretical mechanical model with detailed numerical simulations and field microseismic monitoring to characterize the evolution of hazardous zones throughout the mining process.
Investigating the Mining and Fault Conditions
The 1310 working face lies at an average burial depth of 770 m, with a strike length of about 850 m and a dip width of 190 m.
Two major faults, the Changzhuang East Fault and FY7 Fault, intersect the working face. The Changzhuang East Fault has a dip of 60–70° and a throw of up to 45 m, while the FY7 Fault dips at about 70° with a throw of up to 30 m.
The researchers also considered an earlier rockburst that occurred in the belt conveyor drift of the 1301 working face in 2018. During the event, severe deformation and damage occurred in the roadway, including complete collapse of support sections, substantial roof subsidence, rib intrusion, and deformation of roof beams.
A microseismic event with an energy of 1.7 × 106 J was recorded during the incident. This field event provides an important engineering reference for understanding the conditions associated with rockburst development.
The researchers established a mechanical model to estimate stress within the irregular coal pillar. The model considers the load transferred from the overlying strata and the effects of the adjacent goafs.
From this, the team classified the calculated safety factor into different rockburst-risk levels. For the studied mining conditions, the safety factor ranges from approximately 3.3 to 4.2, placing the pillar within the study's defined medium-risk range and indicating elevated potential for rockburst development.
Tracking Stress Evolution During Face Advance
The researchers developed a three-dimensional numerical model measuring 1000 m × 800 m × 150 m, incorporating four faults, with 1.55 million nodes and 1.28 million elements. The simulation reproduced the actual mining sequence, beginning with excavation of the 1306 working face and followed by progressive advancement of the 1310 working face at 50, 100, 190, 250, 380, 593, and 850 m.
The results showed that faults altered stress transfer and produced localized concentrations within triangular zones formed by fault, goaf, and roadway intersections.
The FY7 fault's acute-angle triangular zone remained a major stress-concentration area throughout mining. Peak stress increased from 38–42 MPa during the initial 50–100 m advance to 47 MPa at 190 m during the square-off stage.
After a slight decline, stress increased again as the working face entered the expansion section, reaching about 53 MPa at 850 m after the coal-pillar width decreased from 158 to 106 m.
The researchers used the Mohr–Coulomb criterion to assess fault activation. This allowed them to determine when mining-induced stress could cause the fault to become mechanically capable of slipping.
At 190 m, stress in the FY7 fault zone reached 44–47 MPa, entering the critical activation value of about 44 MPa. After the pillar narrowed, stress increased to 48–52 MPa, exceeding the critical range of 42–45 MPa and indicating conditions for fault shear activation.
The study therefore links static stress accumulation with potential dynamic loading from fault slip, creating elevated rockburst risk in fault-intersected triangular zones. Microseismic monitoring further identified high-event-density zones around fault intersections and the narrowed pillar, closely matching simulated high-stress regions.
These findings demonstrate that pillar width, fault geometry, and mining-induced stress superposition jointly control the distribution of rockburst risk.
Toward Safer Deep-Mining Operations
Identified hazard zones require a combination of pressure-relief measures, stronger support, controlled mining rates, and enhanced monitoring. Pressure-relief measures include drilling or blasting in residual bottom coal, pressure-relief boreholes in fault-cut roadway areas, and roof-cutting blasting boreholes.
The researchers recommend limiting the working-face advance rate to 2.4 m/day when the face is within 100 m of a fault. Enhanced monitoring should combine borehole stress measurements with microseismic and anchor-cable monitoring, supported by drill-cuttings observations in key hazard zones.
Overall, the study demonstrates that coal-pillar width controls the overall increase in stress, while fault structures strongly influence the location of local stress concentrations.
By integrating theoretical stress calculations, numerical simulation, fault-activation analysis, and microseismic monitoring, the research provides a systematic approach to identifying critical zones and supporting safer deep-mining operations in irregular, fault-intersected coal pillars.
Journal Reference
Zhang, Y., Li, D., et al. (2026). A risk analysis of irregular coal pillars subjected to impact from multiple fault cutting in deep mines. Scientific Reports. DOI: 10.1038/S41598-026-70669-1. https://www.nature.com/articles/s41598-026-70669-1.
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