Stability Analysis and Control Methods of a Layered Roof of Gob-Side Entry in Inclined Rock Strata

In view of the instability of a layered roof of the gob-side entry in inclined rock strata, with the engineering background of the gob-side entry with a small-width coal pillar in Xutuan Mine, the deformation and failure characteristics of the layered roof and the control measures in inclined rock strata are studied by comprehensively adopting field investigation, numerical calculation, theoretical analysis, and engineering tests. The results show the following. (1) After the instability of the layered roof, an unstable zone, a substable zone, and a stable zone are formed accordingly in the surrounding rock from shallow to deep. The unstable zone is an active area in terms of roof deformation and is the main object in the surrounding rock control. The substable zone has a macro control effect on roof deformation. The stable zone is the main bearing structure of the roof. (2) The rock structure has a significant regulatory effect on roof deformation and damage. As the thickness of the layers increases, the bearing capacity of each layer increases and the overall strength of the roof increases. At the same time, the influence range of the substable zone increases, which has a restraining effect on the expansion of the unstable zone. (3) The maximum deformation of the roof decreases exponentially with the increase in thickness of the roof rock beam, increases linearly with the increase in lateral pressure and roof load, and increases exponentially with the increase in entry span. (4) Based on the "two enhancements and one weakening" surrounding rock control strategy, a support system with "high-strength bolts and cables, shotcrete, and anchor grouting" as the core is proposed. The results of field tests indicate that the designed support scheme effectively controls the deformation of the layered roof and achieves long-term stability of the gob-side entry with a small-width coal pillar.