Study on optimization of key parameters of thick hard roof cutting and retaining roadway in inclined coal seam

To address stress concentration in mining roadways, particularly in the inclined, thick, and hard roof, and lessen the impact of sudden overlying strata collapse, a comprehensive study was conducted on the 1301N transport roadway in No.6 Great Wall Mine. The research utilized various methods such as theoretical analysis, numerical simulation, and field monitoring to optimize the key parameters of roof cutting and roadway retaining, leading to improved control of the surrounding rock and reduced risk of impact disturbance. Firstly, based on field geological data, the theoretical minimum roof-cutting height and angle of the 1301N transportation gateway were calculated using the coefficient of rock crushing and swelling and masonry beam theory. Furthermore, in order to confirm and enhance the accuracy of the theoretical findings, we utilized PFC^2D numerical software to create a model of the roof-cutting retaining roadway situated in the No.1301N working face. By employing the control variable approach, we studied the response characteristics of roof stress, displacement, and surrounding rock fabric tensor of the retaining roadway at various roof-cutting heights and angles. The analysis results indicate a logarithmic relationship between cutting height and pressure relief effect. The effect increases with height, but growth amplitude decreases. There is an “S” growth relationship between the roof-cutting angle and the pressure relief effect. The pressure relief effect first increases and then decreases with the increase of the roof-cutting height. The change law between pressure relief parameters and pressure relief effect reveals that there is an optimal value for the selection of the roof-cutting height and an optimal solution for the selection of the roof-cutting angle. Based on the results of theoretical analysis and numerical simulation, it is determined that the most suitable roof-cutting height is 13 m, and the optimal roof-cutting angle is 10°. The field monitoring shows that the control effect of the surrounding rock under the roof-cutting parameters is good, and the deformation of the surrounding rock of the retaining roadway is small. It can effectively meet the mining demand of the next working face and verifies the effectiveness of optimizing the roof-cutting parameters. This provides a theoretical basis and practical reference for the selection of the parameters of roof cutting and retaining roadway under similar geological conditions.