Abstract
Hydraulic fracturing is an effective mean to prevent coal bumps in deep coal mining. The calculation of stress redistribution of coal sidewall after hydraulic fracturing can evaluate the fracturing effect and provide a reference for the hydraulic fracturing scheme design. In this paper, a theoretical model of stress redistribution of roadway sidewall after hydraulic fracturing is established with considering the effect of crushing zone. And the influences of the water injection length and the fracturing radius on the stress redistribution of roadway sidewall are investigated. The results show that the water injection section should be set at a deeper position with considering the existence of the crushing zone. The coal roadway sidewall after hydraulic fracturing is divided into five zones: the crushing zone, the shallow plastic zone, the pressure relief zone, the deep plastic zone, and the elastic zone. The stress redistribution law is obviously affected by the water injection section length and fracturing radius. With the increase of water injection length or fracturing radius, the pressure relief effect is more evident, but the axial force of rockbolt increases gradually. In order to acquire a better pressure relief effect, the matching of the water injection length and the fracturing radius should be considered crucially in the hydraulic fracturing design for preventing coal bumps.
Highlights
Coal bump is a typical dynamic disaster with sudden and violent ejection of coal during deep coal mining, which seriously threatens the safety of people and equipment of coal mines [1,2,3,4]
Pressure relief caused by hydraulic fracturing in coal roadway sidewall is one of the most effective means to prevent coal bumps
Stress redistribution of roadway sidewall after hydraulic fracturing in deep coal mining was studied, which could provide a guidance for the hydraulic fracturing scheme design. e main conclusions are shown below
Summary
Coal bump is a typical dynamic disaster with sudden and violent ejection of coal during deep coal mining, which seriously threatens the safety of people and equipment of coal mines [1,2,3,4]. E hydraulic fracturing method can reduce the risk of coal bump disaster effectively by transferring the high stress in coal seam to a further position away from the roadway boundary [6] and has played an important role in the coal bump prevention [7,8,9]. Coal damage caused by water pressure changes the stress distribution of the roadway sidewall [20, 21]. Rough the calculation of the stress distribution, the pressure relief effect of hydraulic fracturing can be evaluated, and it provides a theoretical basis for designing an effective and reasonable hydraulic fracturing scheme. Hydraulic fracturing can reduce the high stress of the roadway sidewall and cannot meet the energy conditions of coal bumps. Stress redistribution of surrounding rock can reflect the pressure relief effect. The influence of different length of water injection section and different fracturing radius on stress redistribution of roadway sidewall is investigated by numerical simulation
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