Mechanism and practice of roof strip weakening method for preventing rockburst in central roadway

Hard roof is a superior energy storage body but can easily induce rockburst as it releases a large amount of elastic energy when breaking. Taking the central roadway of the Mengcun coal mine in Shaanxi as the research object and considering its geological occurrence characteristics, coal seam physical mechanical properties, roadway spatial relationship and in-situ stress occurrence characteristics, it is found that its high ground stress occurrence, strong impact tendency, stress concentration caused by multi roadway arrangement, and overlying hard roof that is prone to store energy are the main factors leading to the frequent occurrence of rock burst in the central roadway. Based on this, the roof strip weakening method is proposed to create a strip weakening range parallel to the axis of the roadway along the bedding direction to prevent the roadway rockburst. According to the mechanical model and analysis, it is demonstrated that the method can effectively reduce energy storage, increase energy dissipation and local structure adjustment. Additionally, the ultra-long hole hydraulic fracturing technique is used to form the weakening area of the roof strip in the hard roof in the central roadway. By employing the SOS microseismic monitoring system, the energy level and appearance characteristics of microseismic events in a certain area before and after the measures are compared. The results show that there are no occurrence of microseismic events with energy greater than 10⁴ J in the monitoring area, and the energy of other magnitudes also decreases significantly, the energy concentration zone changes correspondingly. These results demonstrate that the roof strip weakening method can effectively contain the potential of rockburst, and provide a new technical means for roadway rockburst prevention.