In view of problems with roadways with a compound roof, such as the occurrence of instability in the roof strata, ease of separation of the layer caving, difficulty of maintenance, and poor safety, we established a mechanical calculation model of a roadway with compound roof using the elastic mechanics theory, taking the stability control of a roadway with compound roof at a coal mine in Guizhou Province, China as the research background, and based on the actual characteristics of the coal seam and the roof and floor slate. Expressions of the separation layer and instability limit load of compound roof were derived, and the calculation and verification were carried out in combination with the actual conditions. By means of numerical simulation, the distribution and evolution laws of stress, displacement and plastic zone of roadways with a compound roof were studied, and the deformation characteristics and instability mechanism of roadways with a compound roof were revealed: (1) in early stage deformation of roadway, the amount is large, the speed is fast, and the scale is wide; (2) compound roofs are vulnerable to abscission and instability, the bearing capacity of the two sides is low due to softness and cracking, the shear failure of side angles and vertex angles weakens the strength of surrounding rock, and the self-bearing capacity of surrounding rock is low; (3) the bolt and anchor bear relatively large tensile force, and the support structure is easy to be broken up. On this basis, the stability control principle of a roadway with compound roof tunnel was put forward: fast and timely support; high-strength bolt strong support; improving the stability of the roof and the bearing capacity of the two sides; restraining the shear failure of the key bearing parts such as the side angles and the bottom angles, and targeted stability control technology for roadways with a compound roof was developed. The field industrial test showed that the deformation of this roadway with a compound roof was effectively controlled and the overall stability of the roadway was effectively improved. The results of this study could provide useful reference for a roadway with a compound roof under similar conditions.

As a widely-used method of digging roadways in China, gob-side entry driving features specific advantages, such as a high recovery rate and good isolation effects. However, under the condition of hard overburden, the excessive bearing pressure of small coal pillars will easily cause serious internal damage in the coal and the run-through of the plastic zone, leading to harmful gas leakage in the goaf. Therefore, based on the engineering background of small coal pillars in the 18506 working face of Xiqu Coal Mine, this paper comprehensively adopts theoretical analysis, numerical simulation, industrial tests, and other methods, analyzes the evolution mechanism of isolated bearing and plastic fracture areas of small coal pillar under hard overburden, studies the influence law of hard overburden cutting parameters on the isolation and stability of small coal pillars, and puts forward the technology of actively cutting the top to weaken the stress concentration of coal pillars under hard overburden. With the reasonable cutting parameters determined, the controllable mechanism of hydraulic fracturing cutting under hard overburden further revealed, and the hydraulic fracturing cutting technology with “controllable cutting orientation of hydraulic fracturing with local stress field intervention” formed as the basic core, the stress situation on the roof is improved, realizing the stability control of the coal pillars for the roadway protection, and avoiding gas leakage and other disasters caused by small coal pillar destruction.

With the typical composite roof roadway and roof fall accidents in the Guizhou Province of China as the research background, the expression of damage parameters of composite roof was deduced according to Weibull statistical distribution, generalized Hooke’s law and Mises yield criterion, and the influence of shape and scale parameters of Weibull on damage characteristic was discussed. Based on the infinite slab theory, the expressions of deflection and layer separation of each layer of the composite roof were obtained, the critical load expression of each delamination was determined, and the influence of roadway width, overlying strata load, elastic modulus, shape parameters and scale parameters on the stability of composite roof was explored. The research shows that the bolt support can effectively reduce the layer separation between the composite roofs and enhance the stability of the composite roof. On this basis, it is proposed that for the surrounding rock control problem of roadways with composite roof, the active support technology with bolts as the core should be adopted.