Effect of Saturation Time on the Coal Burst Liability Indexes and Its Application for Rock Burst Mitigation

Abstract

Coal seam water infusion is one of the widely used techniques for rock burst mitigation, and the saturation time of coal is one of the essential factors influencing the effectiveness of water infusion. To analyze the effect of saturation time on coal burst liability indexes, bursting liability indexes of coal specimens taken from No. 2 mining face in Changgouyu Mine in Beijing were tested under natural state and different saturation time. Compared with coal specimens under natural state, the uniaxial compressive strength, elastic strain energy index, and bursting energy index all decrease in different degrees as the saturation time increases. The dynamic failure duration, however, shows an opposite tendency. When the saturation time is 0–6 days, the bursting liability indexes vary significantly, but when the saturation time is longer than 6 days, this phenomenon is not very obvious. When the saturation time increases from 0 to 6 days, the uniaxial compressive strength, elastic strain energy index, and bursting energy index decreases from 18.31 to 7.15 MPa, 2.59 to 1.25, 3.04 to 1.20, respectively, but when the saturation time increases from 6 to 8 days, their corresponding increments are only 0.02–0.05. Moreover, the time of coal seam water infusion in No. 2 mining face was designed 6–8 days based on the test results. Practical experiences show that excellent destress effect was achieved by water infusion. After coal seam water infusion, the average moisture content of coal seam increases from 0.85 to 1.26%, and the width of destress zone increases from 0–4 to 0–6 m.