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.
Highlights
According to statistics, steeply inclined coal seams (SICSs) are being mined in more than 100 mines in more than 20 key mining areas in China. e SICS is widely distributed in many coal-producing areas in China, such as Xinjiang Uygur Autonomous Region, Gansu Province, Ningxia Hui Autonomous Region, and Guizhou Province [1,2,3,4], with coal output accounting for about 5% of the total
With the constant increase of depth and intensity of coal mining, mining-induced strata behavior is becoming increasingly intense in horizontal slices of extrathick steeply inclined coal seams, and many coal burst accidents even occurred [5, 6]
Signal amplifier Acceleration sensor Pressure cell slice 7 is 0.6 m, dynamic failure occurs on the roof roadway (Rr) and coal and rock are instantaneously thrown out into the mined-out space
Summary
Steeply inclined coal seams (SICSs) are being mined in more than 100 mines in more than 20 key mining areas in China. e SICS is widely distributed in many coal-producing areas in China, such as Xinjiang Uygur Autonomous Region, Gansu Province, Ningxia Hui Autonomous Region, and Guizhou Province [1,2,3,4], with coal output accounting for about 5% of the total. This study established a theoretical model, conducted the similarity simulation test under combined dynamic and static loads, and performed on-site MS monitoring On this basis, static stress distribution in the extrathick SICS working face before roof breakage and the mechanism of the roof breakage-induced coal burst in the roof roadway were investigated. Is indicates that because of effects of the occurrence structure on the test, stress of coal mass in main key strata and on the roof side of lower slices is higher, which is well coupled with theoretical analysis results. According to pressure cells’ data, consistent with theoretical analysis results, stress on the roof side is obviously higher than that on the floor side, indicating that the test can reflect the actual deformation and failure of coal and rock in the field to some extent. Stress is higher after superposition of dynamic and static loads. is indicates that, in the Static stress (MPa)
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