Research on crack distribution characteristics and control technology of surrounding rock in soft rock roadway under different lateral pressure coefficients

To solve the problem of controlling large deformation of surrounding rock in deep soft rock roadway, the distribution characteristics and deformation mechanism of surrounding rock cracks in soft rock roadway under different lateral pressure coefficients are studied using numerical simulation, theoretical analysis, and field measurement. The results show that under different lateral pressure coefficients, the range of surrounding rock cracks shows three forms: round, oval, and butterfly. No matter what lateral pressure coefficient the roadway is in, the surrounding rock cracks always appear in the plastic zone, and there is a high correlation between the surrounding rock crack range and the plastic zone. The stress characteristics of the surrounding rock in the plastic zone include two main aspects. One is that the direction of the principal stress of the surrounding rock is deflected, which is manifested as an annular distribution of the direction of the maximum principal stress around the roadway. The direction of the minimum principal stress in the upper part of the roadway points to the center of the roadway, and the direction of the minimum principal stress in the lower part of the roadway deviates from the center of the roadway. Second, the ratio of the maximum to minimum principal stress in the surrounding rock is large. Under this stress characteristic, the surrounding rock in the plastic zone has strong shear dilation. The shear dilation makes the crack of the surrounding rock open so that the surrounding rock is squeezed into the roadway space, and then the roadway produces large deformation. Due to the large range of cracks in the butterfly-shaped plastic zone, the shear dilation deformation produced by the butterfly-shaped plastic zone is far more than that of the round/oval plastic zone. According to the crack range of roadway surrounding rock under different lateral pressure coefficients, the corresponding support scheme is put forward. Field experiments show that the support scheme can effectively control the deformation of surrounding rock and meet the requirements of roadway use.