In this study, the roof-cutting-type gob-side entry retaining is introduced, and its application in medium-thickness coal seams is studied. Based on the analysis of the construction procedure and principle, the mechanical model of the retained roadway structure and cantilever beam formed by roof cutting was established, and the support resistance and roof deformation were obtained. In addition, through technological design analysis and numerical simulation, the parameters of roof cutting were determined. The roof-cutting height and angle were designed to be 9 m and 15°, respectively. Flac3 D was used to analyze the stress evolution law under different mining conditions. The stress on the integrated coal side and roof subsidence was lower when the roof-cutting height was 8∼10 m and the cutting angle was 15°. Through field monitoring, the roof pressure, gob-side lateral gangue retaining pressure, anchor cable stress, and deformation of the surrounding rock eventually reached a stable state. This indicates that the roof cutting can effectively cut down the overlying strata over the gob and form a stable entry structure to meet the requirements of the next working face.

Gob‐side entry retaining (GSER) is a popular no‐pillar mining technology that can increase coal recovery rate. We propose the application of high‐strength lightweight (HSLW) concrete to construct the gob‐side support body (GSSB) in NO. 411 inclined working face of Jingang Coal Mine. Firstly, the mechanical model of retained roadway was established, and the calculation for limit angle of GSSB stability and support resistance was mathematically derived. Using the performance test, the optimal proportion of LC50 concrete was determined as follows: the water‐binder ratio was 0.3; the silica fume dosage was not more than 10%; the fly ash dosage was 10–20%; and the sand ratio was 0.45–0.50. Based on theoretical deduction and laboratory analysis, the width of GSSB was obtained to be 0.75 m, and the optimal arrangement of concrete blocks with “two longitudinal and one horizontal, crisscross, and staggered joints” was determined. FLAC3D software was used to study the influence of different widths and material strengths on the surrounding rock deformation and verify the reasonable width and strength of the designed GSSB. Finally, field monitoring of retained roadway shows that the deformation is controlled in a small range, and the retained roadway effect is better, thus proving the feasibility of HSLW for constructing the support body for GSER. Our findings can serve as a theoretical guide for safety and effective implementation of HSLW as GSSB.

To solve the problem of instability and failure of a roadway in the Dianping coal mine working face under the condition of traditional gob-side entry retaining, a mechanical model was established for analysis. The reasons for the damage are as follows: (1) the mining height is high, and the hard thick old roof exhibits large space for rotation and subsidence; (2) the retained roadway includes a large section; and (3) the mining impact is strong, and the adaptability of traditional cable is poor. Therefore, the technologies of “roof-cutting type gob-side entry retaining” were proposed and the principle was analyzed. Numerical simulation analysis of displacement and stress field under two processes was performed. The results indicated that the peak value of side abutment pressure decreased from 20.54 to 18.24 MPa due to the roof cutting (a decrease of 11%). The advance stress was less than the stress value under traditional conditions. When compared with the traditional conditions, the deformation of the roadway decreased by more than 50%. Finally, field monitoring was performed, and the results showed that under the condition of roof cutting, the deformation corresponded to the most severe within the range of 30–80 m behind the working face. After 80 m, the deformation gradually stabilized, and the maximum convergence between the roof and floor was 210 mm. Along the inclined direction, the stress of the hydraulic support in the middle part was the highest, the stress in the uncut side was second highest, and that in the roof-cutting side was the lowest. The periodic weighting interval on the roof-cutting side was the highest, and the transverse influence range of the roof cutting along the working face corresponded to 29.5 m.