Study on Roof Breakage‐Induced Roadway Coal Burst in an Extrathick Steeply Inclined Coal Seam

Abstract

In view of the coal burst induced by roof breakage in the steeply inclined coal seam (SICS) roadway and its mechanism, a mechanical model was established to investigate the distribution of dynamic and static stresses in the coal seam before and after the breakage of a thick hard roof. The aim of this research is to study failure laws of SICS roadways under the superposition of dynamic load induced by roof breakage and asymmetric static load. For this purpose, response characteristics including acoustic emission (AE), static stress, and acceleration were analyzed by applying different dynamic loads to different horizontal slices with a self-made similarity simulation test apparatus under combined dynamic and static loads. The theoretical model and simulation results were verified by analyzing characteristics of coal burst occurrence in the field, microseismic (MS) events, and tomographic imaging of microseismic waves. The study demonstrates the following: (1) The abutment pressure of the roof plays a dominant role in stress distribution of the coal seam slice before the breakage of the thick hard roof with the stress of the roof roadway (Rr) being obviously higher than that of the floor roadway (Rf). (2) High-energy MS events and AE events are concentrated on the roof side after the breakage of the thick hard roof, and coal bursts are more easily induced by the superposition of high dynamic and static stresses on the roof side. Coal burst in the roadway is jointly determined by dynamic and static stresses. Under the same static stress, response characteristics increase with the rise of intensity of dynamic loads. When dynamic stress is the same, coal burst easily occurs in the roadway with high static stress.

The Key Stratum Structure Morphology of Longwall Mechanized Top Coal Caving Mining in Extra‐Thick Coal Seams: A Typical Case Study

“…Based on geological data, the thickness of rock strata controlled by the structure of low cantilever beam and high hinged rock beam is 90.6 m; the first weighting interval of working face is 35 m; integrity coefficient is 0.8; Poisson's ratio of coal is 0.36; the elastic modulus of coal is 2.06 GPa. e corresponding value is substituted into formula (15). e range of internal stress field is 15.4 m. erefore, the breaking position of cantilever beam is 15.4 m away from coal wall.…”

“…According to formula (15), it can be seen that there are three factors, geometric parameters, engineering parameters, and mechanical parameters, which affect the breaking position of cantilever beam. Geometric parameters of rock strata include the thickness of coal seam and immediate roof.…”

“…Zhang [14] presented the relationship between the stability of coal pillar and the reasonable position of splitlevel longwall gob-side entry in extra-thick coal seams. Wang et al [15] studied the relationship between horizontal section mining and rock burst under conditions of steeply inclined and extra-thick coal seam and put forward reasonable measures to prevent rock burst. Based on the specific geological conditions, Wang et al [16] explored the distribution and emission law of gas in extra-thick coal seams.…”

Mechanism of Coal Bursts Induced by Horizontal Section Mining of Steeply Inclined Coal Seams and Application of Microseismic Multiparameter Monitoring in Early Warning

“…A mechanical model was built, as shown in Figure 1. e coal mass was divided into a triangle coal zone on the roof (I), a rectangular coal zone (II), and a triangle coal zone on the floor (III) [18]. e stress of bottom coal was determined by stresses on the roof, the floor, and the scattered overlying rock blocks.…”

Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

“…In summary, although different theories were proposed to study the SDCS mining under different engineering backgrounds, current studies on the SDCS mining still have certain limitations and differences [13,14]. e deformation and fracture formation of the overlying strata in SDCS is nonuniform and asymmetric, and the failure mechanism is complicated [15,16].…”