Paste backfill mining is an significant part of green coal mining, which can improve resource utilization and extend the service life of mines. It is important for solving the “three under, one above” mining problem and avoiding industrial wastes such as coal gangue and fly ash that occupy farmland and pollute the environment. To address the difficult filling problem of a fully mechanized top-coal caving face (FMT-CCF), a new method of partial paste backfill mining is herein proposed. First, the partial paste backfill mining method and implementation steps of the FMT-CCF are introduced in detail. Then, the mechanistic model of the roof beam in partial paste backfill mining is established. Then, the filling structural factors on the filling effect of the 42105 FMT-CCF are determined. Dependent on the assay of the migration law of overlying stratum after filling, numerical simulation analysis is used to research the feature effect of the main filling structural factors on the filling effect. Finally, the paste filling rate, filling width, and filling strength suitable for the 42105 FMT-CCF are obtained. When the filling rate reaches 100%, a significant alteration takes place, resulting in the efficient decrease of the overlying rock stress arch shell’s height. As the width of the filling body expands from 10 m at each end to 20 m, the stress arch of the overlying rock experiences maximum reduction, specifically decreasing by approximately 14 m. When the strength of the filling body is greater than 0.4 GPa, the filling effect is better. This study has important guidance and reference significance for the partial paste backfill of FMT-CCF in thick seam mining.

As a kind of non-coal pillar roadway support technique, gob-side entry retaining is of great significance to improve the production efficiency of a fully mechanized working face. However, the construction of the roadway is often subject to the surrounding rock conditions, the application is mainly concentrated in the nearly horizontal and gently inclined coal seam conditions, and the application in the steeply inclined coal seam conditions is relatively less. This paper is based on the gob-side entry retaining roadway construction of the 58^# upper right 3^# working face in the fifth district of Xinqiang Coal Mine, and describes the investigation in which we measured the advanced abutment stress, mining stress, and roof stress and analyzed the moving rule of roof. On this basis, in this work, we determined the filling parameters and process and investigated the filling effect from the perspective of the deformation of the filling body and the surrounding rock. The results show that the influence range of the advanced abutment stress in the working face is about 20~25 m, the stress in the upper part is intense, and stress in the middle and lower parts are relaxed. The setting load, the cycle-end resistance, and the time-weighted mean resistance at the upper end of working face along the direction of length are the largest, followed by the middle part, and the lower end is the minimum. When exploiting the steep inclined coal seam, the upper part of the working face is more active than the lower part, and the damaging range of overlaying strata is mainly in the upper part of the goaf. With this research, we established the filling mining process in steeply inclined coal seams and determined the relevant parameters. The gangue cement mortar filling can ensure the deformation of the filling body, the surrounding rock of the roadway is small in the process of roadway retention, and the stress of the filling body is also small, which ensure the successful retention of the roadway. This study verifies the possibility of repair-less exploitation and provides a reference for the popularization and application of the gob-side entry retaining technique in steep inclined coal seam.

With the increase in mining depth, the risk of ground pressure disasters in yellow gold mines is becoming more and more serious. This paper carries out a borehole test for the pressure behavior in a non-coal mining area with a mining depth of more than 800 m in the Jiaodong area. The test results show that under a depth of 1050 m, the increase in the vertical principal stress is the same as the increase in the minimum horizontal principal stress, which is about 3 MPa per 100 m. When the depth increases to 1350 m, the vertical principal stress increases by about 3% per 100 m, and the self-weight stress and the maximum horizontal principal stress maintain a steady growth rate of about 3 MPa per 100 m. In addition, based on the test results, the operation of the ground pressure monitoring system in each mine is investigated. The investigation results show that in some of the roadway and stope mines with depths of more than 800 m, varying degrees of rock mass instability have occurred, and a few mines have had sporadic slight rockbursts, accounting for about 5%. There was a stress concentration area in the lower part of the goaf formed in the early stage of mining, and slight rockburst phenomena such as rock mass ejection have occurred; meanwhile, the area stability for normal production and construction was good, and there was no obvious ground pressure. This paper compares the researched mines horizontally as well as to international high-level mines and puts forward some suggestions, including: carrying out ground pressure investigations and improving the level of intelligence, which would provide countermeasures to balance the safety risks of deep mining, reducing all kinds of safety production accidents and providing a solid basis for risk prevention and supervision.