Investigation of the Rockburst Mechanism of Driving Roadways in Close-Distance Coal Seam Mining Using Numerical Modeling Method

The excavation-induced stresses transferred from the panels or pillars in upper coal seams play a key role in the occurrence of rockbursts in driving roadways during close-distance coal seam mining, which has become a common problem and threat to many underground mines. The authors established a 3D finite-difference numerical model via FLAC3D software using the close-distance coal seam mining conditions in the Zofiowka Mine as a case example to reveal the rockburst mechanism in such conditions. The excavation-induced vertical stresses are analyzed, which provides a basis to build a conceptual model to explain the possible source mechanism of the rockburst under such conditions. Nine typical rockburst indicators considering different contributing factors are then selected as the evaluation criteria to assess rockburst potential in the study site. The results suggest that the superposition of multiple excavation-induced stresses of the main drift and tailgate provides an environment for stress concentration and energy accumulation. The side abutment stress induced by mining in the upper coal seam has a strengthening effect to the rockburst occurrence. The great deviatoric stress induced by complex excavating situations is another important exterior cause. A strict calibration procedure should be implemented before using indicators to predict rockburst potential. A methodology was proposed to estimate the location and magnitude of rockbursts combined with numerical modeling, laboratory tests, and feedbacks from the field. The study could provide some references and guidelines for preventing and mitigating rockbursts in underground mines under similar engineering conditions.

Automated summary

Excavation-induced stresses from upper coal seams play a key role in rockbursts during close-distance coal seam mining, with multiple stresses contributing to stress concentration and energy accumulation. External causes like side abutment stress from mining in the upper coal seam and deviatoric stress from complex excavating situations also influence rockburst occurrence. Calibration of indicators is essential for predicting rockburst potential, and a methodology combining numerical modeling, laboratory tests, and field feedback can help estimate and mitigate rockbursts in similar underground mining conditions.