Coupling Instability Mechanism and Joint Control Technology of Soft-Rock Roadway with a Buried Depth of 1336 m

Based on the geological conditions of soft-rock roadway with a buried depth of 1336 m and the data that are achieved by various experimental methods, the multi-factor coupling analysis of the instability mechanism of soft-rock roadway is carried out through theoretical analysis and numerical simulation. Additionally, following the Nishihara model and Drucker–Prague’s modification of Mohr–Coulomb yield condition, the stability control theory of soft-rock coal roadway is analyzed. By fully considering the bearing capacity of each supporting component, the original supporting structure is innovatively examined with crush tube, spherical tray, high-strength bar and steel strip to form a flexible and high-performance bolt supporting structure, and the stability control of 1336 m soft-rock coal roadway is also comprehended. Therefore, the studies have shown that the convergence trend of omnidirectional, strong rheological and large deformation constitutes the essential characteristics of deep soft-rock roadway deformation. The instability process of roadway surrounding rock is accompanied by “domino-effect” similar to that of multi-factor coupling. The irrational design of the support scheme and the destruction of the support structure are the external factors of this effect, although the prominent contradiction between high in-situ stress and the weak bearing capacity of the deep degraded rock mass is the internal factors of this effect. Similarly, the engineering practice and observation data of the new scheme have shown that the deformation coordination of support components and the matching degree of bearing characteristics should be one of the main factors to be considered in the design of deep soft-rock roadway support, high elongation and multiple adjustable characteristics to adapt to the basic characteristics of deep soft-rock roadway deformation. Hence, the construction idea of the new scheme has contributed the satisfactory engineering significances and reference value for optimizing the stress environment of soft-rock roadway and further reducing the support cost.