The use of pre-excavation equipment withdrawal channels (EWCs) at the stop-production line is important for the rapid withdrawal of coal mining equipment. However, during the final mining period, the dynamic pressure of a pre-excavated double EWC is severe, which leads to instability of the surrounding rock around the EWCs. Therefore, in this paper, the methods of field monitoring, theoretical analysis, and numerical simulation were used to systematically study the stress and plastic zone evolution of a double EWC during the final mining period. Firstly, the distribution characteristics of mining abutment pressure and roadway failure modes under the action of mining abutment pressure were analyzed theoretically. Afterward, a FLAC3D mining numerical model was established according to the distribution of rock strata obtained from roof detection. Finally, the evolution laws of the stress fields and plastic zones of the EWCs during final mining were obtained by numerical simulation. The present study suggests that asymmetric stress distribution dominates asymmetric failure of the surrounding rock around the EWCs during the final mining period, and deformation failure within 10 m from the working face to the main EWC (MEWC) accounted for most of the roadway deformation. Based on the research results combined with actual production experience, the stability control technique of the surrounding rock with reinforcement of anchor cables and double-row buttress hydraulic support for the MEWC was put forward. After the field application, the ideal result was obtained.

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The nearby goaf road in the extra-thick coal seam of the Datong mining area exhibits intense strata pressure behavior, which affects the working face mining. Herein, we study the laws of the strata pressure behavior of this road in detail using various methods, including laboratory tests, theoretical analyses, numerical simulation, and field monitoring. Considering the mine pressure characteristics of the nearby goaf road, namely, roof cracking, two-side deformation, and floor heaving, the mechanical tests and theoretical failure analyses of the surrounding rock in the mining-induced non-uniform stress field were carried out. The circular-oval-butterfly failure trend of the surrounding rock in the nearby goaf road under the influence of mining was obtained. The steady failure evolution lateral pressure coefficient (λ=0.5∼1.8) and butterfly mutation lateral pressure coefficient (λ<0.35 or λ>2.1) of the surrounding rock in the nearby goaf road were analyzed. We performed numerical simulation to study the stress field and the plastic zone shape-size characteristics of the surrounding rock during excavation and mining (with or without the top extraction road), and the theoretical law of the mine pressure was obtained for the Tong Xin coal mine. Finally, field monitoring indicates that the mine pressure behavior of the nearby goaf road exhibits spatial differences, namely, the difference between the stresses of the two sides and roof, and the stress characteristics of the deep and shallow surrounding rock. The findings of this study on the mine pressure behavior in the nearby goaf road have great practical significance for targeted measures to control the surrounding rock stability.

The advance area affected by mining (AAAM) of the Lijiahao coal mine is influenced by the superposition of the side and advance abutment pressure, and the roadway roof is considerably damaged. General support technology and equipment cannot economically and effectively maintain the stability of the roadway roof of AAAM. Through field detection, theoretical analysis, and numerical simulation, this study analyzes the structure of the surrounding rock, the evolution characteristics of the regional stress field, the distribution of the surrounding rock plastic zone, and the influencing factors of the plastic zone in the AAAM of the Lijiahao mine. The results show the following: 1) the direct roof and floor of the roadway comprise coal, siltstone, and sandy mudstone, which has low strength and can be easily broken. 2) The maximum and minimum principal stresses in the AAAM reach 2.3 and 1.5 times of in situ stress, respectively, and the ratio of the two stresses reaches 2–8, which causes the shape of the plastic zone of the surrounding rock to turn into a butterfly shape. 3) The principal stress direction of AAAM deflects at a large angle, which causes the deepest failure direction of the surrounding rock to rotate to the roof and floor of the roadway. Accordingly, a self-moving foldable support system is proposed to support the AAAM of the Lijiahao coal mine. The system will not support the roof repeatedly and is suitable for soft rock stratum. In addition, it can also adapt to the heave of roadway floor and avoid dumping. The mechanized operation of the system makes the roof support in AAAM more efficient and safer.

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