Coal-rock combination refers to the coal and rock as a whole, and the failure of the whole structure of the combination is the main cause for the instability of the deep underground engineering. In deep underground engineering, the coal-rock combination is usually under certain hydrogeological conditions, and it is prone to seepage and rheological failure instability accidents due to the long-term action of water and stress. In this study, the creep constitutive model of coal-rock combination considering the influence of moisture content was established based on the Burgers creep model. According to the experimental results of triaxial creep of rock, the relationship between the moisture content and the parameter of the Burgers creep model was derived, and the correctness of the constitutive model in this study was verified. Then, through the C++ language, the core equation of the model was modified, and the numerical calculation of the model was realized by introducing the coal-rock combination creep model considering the influence of moisture content into FLAC3D numerical simulation software. Finally, the model was used to simulate and study the creep characteristics of coal-rock combination with different moisture contents under triaxial loading. The results showed that the stress environment and moisture content have significant effects on the creep characteristics of the coal-rock combination. Under the same stress state, with the increased of moisture content, the strain rate of the coal-rock combination exhibited a non-linear rapid increase in the constant-velocity creep stage, the limit creep deformation and the instantaneous elastic deformation increased, and the viscosity coefficient was significantly decreased. For example, when the axial stress was 5 MPa and the moisture content increased from 0% to 1.5%, the strain rate increased by 44.06%, the limit creep deformation increased by 20%, the instantaneous elastic deformation increased 10.53%, and the viscosity coefficient decreased by about 50%. When the moisture content is 0%, the axial stress increased from 5 to 14 MPa, and the limit creep deformation increased nearly four times. With the increase of moisture content, this value will further expand. The research conclusions can provide a certain reference basis for the long-term stability control of surrounding rock in underground engineering affected by the water.

The floor heave problem is one of the important factors affecting the stability and safety of surrounding rocks of roadways, especially in deep high‐stress mining roadway with soft rock. The return airway of no. 130203 working face in Zaoquan Coal Mine of Ningdong Mining Area in Northwest China is the research object in this study. Firstly, an innovative “relief‐retaining” control scheme of floor heave is proposed, which is the comprehensive measure of “cutting groove in floor + drilling for pressure relief at roadway side + setting retaining piles at the junction of roadway side and floor.” Then, the specific parameters suitable for floor heave control of no. 130203 return airway are determined using numerical simulation method. Finally, the yield monitoring results show that both the deformation of surrounding rocks and the cable force are significantly reduced. The roof falling capacity, floor heave displacement, and thickness increasing value of 0–2 m floor strata are 596 mm, 410 mm, and 82 mm, respectively, which are 43.67%, 67.49%, and 75.38% less than those of the control section. The maximum force of cables at roadway sides is 140.13 kN, about 32.54% less than that of the control section. The results verify the reliability of the proposed “relief‐retaining” control scheme and can provide some reference for the floor heave control of similar roadways.

The superposition effect of the advanced support pressure of the working face in the final mining stage and the lateral support stress of the roadway is a key factor affecting the stability of the retracement channel. To study the stress evolution of the retracement channel under the super-thick nappe and the timing of strengthening support, this paper takes the mining of the 360808 working face in Xinji No. 1 Mine as the engineering background, analyzes the occurrence conditions of the working face and the measured rock pressure law, and constructs a roof structure model of the retreat area. The UDEC discrete element numerical simulation software was used to analyze the evolution characteristics of concentrated stress and the failure law of surrounding rock around the retracement channel under gradual excavation conditions. Based on the relationship between the position of the main roof fracture and the stability of the surrounding rock of the retracement channel, the instability mechanism of the surrounding rock of the retracement channel was revealed. A mechanical model of the surrounding rock of the retracement channel under the condition of a gradient coal pillar was established, and the energy criterion K for the instability of the surrounding rock was obtained. The method of adding anchor cables to strengthen the support of the surrounding rock of the retracement channel was proposed. The results indicate that the accumulation of energy in the surrounding rock of the retracement channel is greater than the internal consumption of energy, which is the direct reason for the instability of the surrounding rock of the retracement channel. The time to strengthen the support of the roof is when the working face is 15 m away from the retracement channel. According to the analysis of on-site monitoring results, the roof convergence and the two-sides convergence before and after strengthening the support were reduced by 90 mm and 140 mm, respectively. Under the strengthening of support, the slope of the retracement channel in the 360808 working face is slight, without roof fall, and the surrounding rock of the channel is effectively controlled, which is of great significance for ensuring the safe application of the retracement channel. It has reference value for the safety production of surrounding mines and is conducive to promoting the sustainable development of local resource-based society and economy.

Coal mine underground reservoir water storage technology is an effective technical way to achieve high efficiency of coal mining and protection of water resources. The stability of coal pillar dam plays a decisive role in the safe and stable operation of underground reservoirs. Mining of adjacent working faces and long-term water erosion are the main influencing factors of stability of coal pillar dam. In this paper, a fluid-solid coupling calculation model for the deformation and evolution of coal pillar dam was established by FLAC3D numerical simulation software and the underground brine reservoir of Lingxin Coal Mine of Shenning group as an engineering background. The paper studied systematically the deformation, failure, and stress evolution of the dam with coal pillars soaked in water for a long time under different working face inclining length, coal pillar width, mining height, and water pressure. The simulation results showed that the degree of deformation and failure of the coal pillar dam continued to increase with the continuous advancement of the working face. The plastic zone of the coal pillar dam was increased by approximately 23.53%, the maximum vertical stress was increased by approximately 95.78%, and the maximum vertical deformation was increased by approximately 68.18%. The influence of each factor on the deformation and failure of overburden strata is quite different. The development range of plastic zone, the maximum vertical stress, and the maximum vertical deformation were increasing with the increased of working face inclined length and mining height. The increasing width of coal pillar would lead to the decrease of maximum vertical stress. The increase of water pressure would lead to the decrease of maximum vertical deformation. It can be seen that the inclined length of the working face is the main factor affecting the deformation and failure of the coal pillar dam. Coal pillar width and mining height are the main factors affecting the development of plastic zone. This study reveals the law of deformation and fracture evolution of coal pillar dam under different mining conditions, which can provide a reference for the design of coal pillar dam of coal mine underground reservoir.