Instability mechanism and control measures of surrounding rock in deep tunnel under high lateral pressures

Aiming at the destructive phenomenon of the 958 horizon of Jinchuan Mine, through theoretical analysis, mechanical calculation, numerical simulation and field investigation, the deformation process of the surrounding rock under different lateral pressures is simulated, the instability mechanism of the surrounding rock and the failure mechanism of support are revealed, and the control measures of stable tunnel under high lateral pressures are discussed. The scheme of combined arch-beam and support is proposed, calculation of pressure arch of the surrounding rock is improved, and the mechanical model for floor-beam is established. Using the differential equation, the inversion of support parameters is performed. The results show that the proportion of roof-floor deformation is positively correlated to the coefficient of lateral pressure, and the stress state of the surrounding rock changes with the coefficient of lateral pressure. The high lateral pressure and the concentrated stress are the primary causes for the instability of rock with low relative strength and the failure of support with high correlation. Considering the overall and partial strengths, improving the poor stress state and enhancing the bearing capacity of the surrounding rock are the key to controlling the stabilization of tunnel. The interaction between the stress of bolt and the surrounding rock which forms bearing arch can mitigate the stress. The floor-beam braces the footing and weakens the extrusion trend by the two sides. The monitoring results show that the deformation rate and the range of tunnel decrease, and the overall stability of tunnel is controlled.