Coalbed methane (CBM) development involves multiple interacting physical fields, and different coupling schemes can lead to distinctly different production behaviors. A thermo-hydro-mechanical model accounting for gas–water two-phase flow and matrix dynamic diffusion (TP-D-THM) is developed and validated, achieving an error rate below 10%. By embedding the numerically estimated reservoir physical parameters of the Qinshui Basin into the numerical model, multi-field couplings during CBM production, the evolution of physical parameters, and the depth-dependent effects on production characteristics were revealed. The main findings are as follows: The inhibitory effect of water on CBM recovery consistently exceeds the promoting effect of temperature. As burial depth expands, the inhibitory effect first diminishes, then intensifies, ranging from 19.73% to 28.41%, while the thermal promotion effect exhibits a monotonically increasing trend, fluctuating between 8.55% and 16.33% and stabilizing below 1000 m. Temperature and burial depth do not alter the trend in gas production rate. For equilibrium permeability, reproducing a decrease–increase–decrease rate pattern requires explicit inclusion of water and matrix-fracture mass exchange terms, which can explain why different scholars obtained varying gas production rate trends using the THM model. Matrix adsorption-induced strain is the primary control on permeability evolution, and temperature amplifies the magnitude of permeability change. The critical depth essentially reflects the statistical characteristics of reservoir petrophysical properties. A dimensionless critical depth criterion has been proposed, which comprehensively considers reservoir pressure, permeability, and a fractional coverage index. For burial depths ranging from 650 to 1350 m, the TP-D-THM model can be simplified to the gas-mechanical model accounts for matrix dynamic diffusion (D-HM) with an error below 5%, indicating that thermal and water effects nearly cancel each other.

Gob-side roadways driven along the floor while retaining top coal in thick soft coal seams are prone to instability under strong mining-induced dynamic loading. To clarify the instability mechanism and develop an effective control method, the 1609 return airway of Jiulishan Mine was investigated using field survey, borehole imaging, FLAC3D numerical simulation, industrial testing, and field monitoring. The results show that, under the combined effects of large mining height, insufficient filling of the gob by the caved immediate roof, weak retained top coal, and low coal strength, shear failure planes tend to develop within the narrow coal pillar and extend from the gob-side roof toward the floor. Once the dominant shear plane cuts through the pillar, the overall bearing structure is destroyed, leading to shear slip, asymmetric rib deformation, roof subsidence toward the coal-pillar side, and rib–roof coupled instability. Based on a multi-index evaluation of pillar load-bearing capacity, plastic zone development, stress concentration, roadway deformation, and coal recovery, a 3 m coal pillar was determined as the rational width. A coordinated “narrow coal pillar + cross-rib anchorage” scheme was proposed, and field verification confirmed its effectiveness in controlling roof separation, roadway surface displacement, and internal surrounding-rock damage.

To address the large deformation and instability of gob-side entry roofs in soft, thick coal seams induced by residual cavities left by hydraulic flushing, the 1609 working face of Jiulishan Coal Mine was selected as the engineering background. Field investigation, numerical simulation, and industrial field testing were combined to investigate the deformation and failure characteristics of surrounding rock and the corresponding control technology for gob-side entries with cavity-bearing roofs. The results indicate that residual cavities created by hydraulic flushing disrupt the stress transfer path within the roof, causing stress field distortion and expansion of tensile stress zones, thereby significantly weakening the roof load-bearing capacity. As the cavity size increases, the surrounding rock deformation and plastic zone continuously expand. When the cavity size exceeds 1.0 m, roof subsidence exhibits a nonlinear increase, and the fractured zone around the cavity connects with the roof plastic zone, forming a continuous failure band that serves as the key factor leading to surrounding rock instability. Based on the deformation characteristics of the cavity-bearing roof, namely shallow fragmentation, deep-seated separation, and structural instability, a collaborative control technology consisting of multi-level cable bolts, steel-beam reinforcement, and grouting through injection pipes was proposed. By establishing a shallow–intermediate–deep hierarchical load-bearing structure and reinforcing the fractured cavity zone through grouting, the technology reconstructs the surrounding rock load-bearing system and optimizes the stress environment. Field application results show that, for a roof containing a 1.5 m cavity, the maximum roof subsidence and separation were controlled within 102 mm and 55 mm, respectively, and the roadway maintained a stable condition throughout the monitoring period. The findings provide both a theoretical basis and engineering guidance for surrounding rock control of gob-side entries with cavity-bearing roofs in soft, thick coal seams.