Abstract
Adopting yellow mud as barrier layer materials, coal and gas delay outburst experiments under conditions of geostress and gas accumulation disturbance were carried out by using self‐developed simulation system, to find out roles of geostress and gas pressure played in the process of the delay outburst and ways to predict it, through analysis of variations of gas pressure, and AE characteristics during the process. The results show that after the geostress increased by 0.11 MPa from 1.80 MPa, an outburst occurs, while in gas accumulation situations, the gas pressure increase of 0.27 MPa from 0.67 MPa induces an outburst; hence, geostress is one of the dominant factors impacting an outburst occurrence. The lasting time of the outburst triggering under geostress disturbance is shorter than that under gas accumulation disturbance, while the duration of the outburst development under gas accumulation conditions is longer than that under geostress conditions. Coal seam breakage by geostress is the precondition for an outburst risk, and gas expansion energy is the dominant parameter influencing the duration of the outburst development. The AE signals show distinctive features in different stages of the outburst under geostress disturbance. At the preparation stage of the outburst, the AE signals increase sharply but have a low intensity and then drop to a lower balance level. At the triggering stage, the AE signals become active and increasing until up to the peak where the outburst occurs, and the intensity is highest.
Highlights
Coal seam breakage by geostress is the precondition for an outburst risk, and gas expansion energy is the dominant parameter influencing the duration of the outburst development. e acoustic emission (AE) signals show distinctive features in different stages of the outburst under geostress disturbance
Self-developed large-scale coal and gas outburst simulation platform was used to simulate the delay outbursts [15]. e temperature sensor and gas pressure sensor installed in the device can synchronously detect the variations of the temperature and gas pressure in the coal body, and gas pressure sensor is installed in the middle area inside the test box
In the process of outburst development (Stage cd), a large amount of pulverized coal was quickly ejected from the chamber, the gas pressure decreased instantly, the accumulated energy in the coal seam fractured the coal and ejected them out, the adsorbed gas continuously desorbed into the free state and constantly broke the coal masses, and the temperature declined significantly
Summary
E hard yellow mud has a certain strength that can bear some degree of stress changing inside the coal mass to prevent an outburst accident. It can maintain in the plastic state under existing loading conditions and realistically simulate the plastic deformation and failure of the coal seam. E simulation experiments were carried out for three times, and the actual gas pressure was 0.67 MPa. e instantaneous outburst occurred when the thickness of the yellow mud was 10 mm, and delay outbursts took place when the thickness was 15 mm. E simulation experiments were carried out for three times, and the actual gas pressure was 0.67 MPa. e instantaneous outburst occurred when the thickness of the yellow mud was 10 mm, and delay outbursts took place when the thickness was 15 mm. e two simulation experiments under the conditions of 15 mm thickness of the yellow mud were mainly discussed in this work
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