Mechanism and Prevention of Rockburst in Steeply Inclined and Extremely Thick Coal Seams for Fully Mechanized Top-Coal Caving Mining and Under Gob Filling Conditions

Abstract

The steeply inclined and extremely thick coal seams (SIETCS) under the condition of gob filling frequently suffer from the occurrence of rockbursts. Figuring out the mechanisms of rockbursts under this condition for taking targeted measures to mitigate rockburst hazards in SIETCS is of great significance. Using the typical SIETCS with an average dip angle of 87° at Wudong Coal Mine (WCM) as a case study, a mechanical model and elastic deformation energy (EDE) function of a “steeply inclined suspended roof structure” was developed, and the influence factors were analyzed by theoretical analysis. Simultaneously, the rockburst risk assessment was carried out based on the theory of a rockburst start-up. The pressure relief measures are optimized by comparing the pressure relief effects of three kinds of destress blasting schemes. The results indicate that the damage characteristics of rockburst are mainly floor heave, the sidewall’s inward deformation and roof subsidence. The damage degree of headentry on the roof side is more severe than that of tailentry, and the resultant impacts showed the directionality from the roof side to the coal side. The steeply inclined and suspended roof breakage is one of the main causes for the occurrence of rockbursts. The EDE of the roof increases with an increasing dip angle of the coal seam from 0° to 72.6° and then decreases as the dip angle increases. Furthermore, that increase is accompanied by the decrease of the lateral pressure coefficient and the supporting force coefficient. The EDE stored in the roof is sufficient to cause roof breakage and induce rockburst after the complete roof exceeds a certain length. The mechanism of rockburst in SIETCS for fully mechanized top-coal caving mining under gob filling conditions was proposed, i.e., “high compressive stress concentration plus breakage of the suspended roof-induced stress” rockburst, and this is further verified by ground destruction, microseismic (MS) monitoring and numerical modeling. The results also indicate that alternate deep and shallow hole-blasting modes are more suitable for pressure relief in SIETCS.

The Mechanical Criterion of Activation and Instability of Normal Fault Induced by the Movement of Key Stratum and Its Disaster‐Causing Mechanism of Rockburst in the Hanging Wall Mining

“…[8][9][10]. Besides, shallow coals are gradually exhausted; the deep mining geological conditions are more complex; faults, folds, and other geological structures are concentrated, and the development situation of coal resources is extremely severe [11][12][13][14]. e study has shown that the occurrence of coal mine rockburst is closely related to geological structure and other factors; it is easy for rockburst to enter the concentrated burst, especially in the vicinity of faults [15][16][17][18].…”

Stress Relief and Support for Stability of Deep Mining Roadway with Thick Top Coal in Hujiahe Coal Mine with the Risk of Rock Burst

“…Wang et al [17] outlined the evolution mechanism of two different types of rock bursts and proposed measures such as caving mining, deep hole blasting, and large diameter drilling, which provided a basis for the risk control of rock burst disasters in subsequent mining activities. He et al [18] studied the mechanism of rock burst in steeply inclined extrathick coal seam and optimized the pressure relief measures by comparing the pressure relief effects of three stress blasting schemes. Cui et al [19] used a physical similar material simulation experiment and acoustic emission monitoring method to study overburden failure law and acoustic emission characteristics in the coal mining process.…”

Investigation on Rock Strata Fracture Regulation and Rock Burst Prevention in Junde Coal Mine

“…Wang et al [12] studied the failure mechanism of marble under cyclic loading and unloading conditions and provided theoretical basis for rock dynamic disaster prediction. With the development of mining activities, the self-stable state of high stress balance of coal pillar is easily broken by the impact energy formed by the sudden collapse of key strata [13,14]. erefore, the rock burst of coal pillar in overlying coal area is the result of static load and dynamic load [15,16].…”