Mechanism and Evolution Control of Wide Coal Pillar Bursts in Multithick Key Strata

Abstract

Coal mine pillar burst frequently occurs in Western China, which seriously restricts safe production. This paper takes the 35 m coal pillar of the 3102 working face of MKQ coal mine as the engineering background. The mechanism and evolution control of pillar bursts in multithick key strata are studied using field investigation, theoretical analysis, and numerical simulation. The mechanism of dynamic and static stress-induced pillar bursts was revealed combining the “O-X” broken features for key strata and numerical simulation of pillar stress evolution. A prevention scheme is put forward for strata presplit blasting and adjusting coal pillar width to minimize the dynamic and static stresses. The results demonstrate the following. (1) In the multithick strata, the first and second near-field subkey strata have perpendicular “O-X” broken features, whereas the third far-field subkey has parallel “O-X” broken features. The working face has three kinds of periodic weighting phenomena: long, medium, and short. (2) The simulated vertical stress curve of 35 m coal pillar goes through three states: two-peak, asymmetric trapezoidal and symmetrical trapezoidal shape with the different advancing position of working face. The stress concentration is extensively promoting a high-risk area for rock burst. (3) The coal pillar burst was induced by the superposition of energy released by the key strata breaking and the elastic energy accumulated in the wide coal pillar. (4) The monitoring data showed that the long, medium, and short periodic weighting steps of multithick key strata are 141.6 m, 43.2–49.6 m, and 17.6–27.2 m, respectively. The microseismic events energy, frequency, and stress of hydraulic support increment are the highest during the long periodic weighting, and the spatial distribution of microseismic events coincides with the stress concentration area. The theoretical analysis is confirmed with the field practice.

Evolution characteristics of overburden structure and stress in strong mining of the deep coal seam: a case study

“…The overburden structure is gradually developed from the preliminary vertical "O-X" type to the "O" type with continuous mining through the previous investigation of the evolution law of the overburden spatial structure (Dou and He, 2012;Guo and Cao, 2021;Ma and Yuvan, 2021). The formation of stress concentration in front of the working face is likely to cause a rock burst as the overlying load is transferred to the coal mass (Li and Wang, 2016;Yang and Liu, 2019).…”

Influence of Key Strata on the Evolution Law of Mining-Induced Stress in the Working Face under Deep and Large-Scale Mining

“…The distribution of energy accumulation and fracture positions before and after the fracture of overlying key strata has been derived, and the energy release of fractures in each stratum has been calculated [4]. The mechanism and evolution control of pillar bursts in different thickness key strata have been studied using field investigations, theoretical analysis, and numerical simulation [5]. The spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam theory [6].…”