In view of the difficulty of the surrounding rock control of retaining a roadway along a goaf, this paper takes the 5504 working face of the Hongshuliang Coal Mine as the engineering context. The uniaxial compressive strength and tensile strength of concrete filling material in the retained roadway are determined by laboratory tests. Through theoretical analysis, field investigation, numerical simulation and field measurement, the distribution characteristics of deviatoric stress and damage zone of the roadway surrounding rock in the mining process of the 5504 working face are studied here. Based on the failure of rock mass element caused by deviatoric stress tensors, the study shows that the thickness of the concrete wall is 2.2 m and the compressive strength of the concrete wall can reach 10.87~11.64 MPa in 3 days to 4 days, which can meet the support strength of the retained roadway. From the position of 90 m in front of the working face to the position of 100 m behind the working face, the distribution form of the roadway surrounding rock deviatoric stress is: symmetrical butterfly shape → single butterfly shape → narrow oblique strip → oblique 8 shape → wide oblique strip shape. When the distance between the retained roadway and the working face is 49 m, the retained roadway tends to be stable. Based on the distribution characteristics of the deviatoric stress outline line and the damage zone outline line of the retained roadway surrounding rock, the retained roadway surrounding rock is divided into three regions, and the combined support technology of “bolt + anchor cable + single pillar + reinforcement combined with steel plate to strengthen concrete wall” is proposed. Through field engineering practice, the maximum displacement of roof, floor, solid coal side and concrete wall side in the retained roadway is 136.6 mm, 78.8 mm, 62.3 mm and 43.3 m, respectively, and the surrounding rock control effect of the retained roadway is good.

Research and Application of Prefilled Concrete Wall to Reduce the Size of Stopping Mining Coal Pillar: The long-term stability and width of stopping mining coal pillar have an important influence on mine safety production. In view of the type spatial structure of stop mining position of 6105 working face in Hongshuliang Coal Mine, the mechanical equilibrium, the distribution law of stress concentration factor, and the distribution characteristics of elastic zone of filling body-remaining stopping mining structure are studied by means of theoretical calculation, FLAC3D numerical simulation software, and field measurement. The research shows that (1) the concrete filling body can protect the remaining stopping mining coal pillar, the surrounding rock of the retracement channel, and the surrounding rock of the main roadway, and the width formula of filling body - remaining stopping mining coal pillar structure is deduced; (2) in the retracement channel, increasing the internal friction angle and cohesion of coal can eliminate the spalling and large deformation of surrounding rock; (3) according to the comprehensive analysis, the width of the filling body-remaining coal pillar structure is 25m, in which the width of the concrete filling body with uniaxial compressive strength of 50MPa is 6m, and the recovery rate of stopping mining coal pillar is increased by 52.5; and (4) field measurement shows that in the retracement channel, there is no spalling and large deformation. In the auxiliary main haulage roadway, the maximum deformations of roof, floor, solid coal side, and stopping mining coal pillar side are 46mm, 18.4mm, 55.9mm, and 74.8mm, respectively.

In order to solve the problem that the surrounding rock control of the pre-excavation double-retracement channel is difficult and a large number of coal pillars cannot be recovered. Taking chuancaogeban coal mine as the engineering background, the mechanical model in the process of gradual connection between coal mining face and main withdrawal channel is constructed, and the response characteristics of surrounding rock in withdrawal channel are simulated and verified by FLAC3D numerical calculation model. The instability mechanism of this kind of roadway is revealed, and a comprehensive stability control technology of surrounding rock and the technology of recovering all coal pillars are proposed, and the field engineering verification is carried out. The results show that when the coal mining face is close to the main retracement channel, when the distance between the coal mining face and the main retracement channel is 4 m, the coal body between the coal mining face and the main retracement channel enters an unstable state. Using 8 m wide filling wall to replace the coal pillar between the main retracement channel and the auxiliary retracement channel can ensure the stability of the surrounding rock of the two retracement channels after the coal mining face passes through the main retracement channel. In addition, the retained auxiliary withdrawal channel also has the functions of auxiliary production and coal pillar recovery, and finally realizes the technology of pre-excavation double withdrawal channel without coal pillar abandonment. As the coal mining face gradually approaches the main retracement channel, the surrounding rock stress of the main retracement channel and the auxiliary retracement channel has significant dynamic development. Based on the development law of the deviatoric stress of the surrounding rock, the combined control technology of ‘ pre-cutting roof + high water material pillar + grouting reinforcement + single pillar + metal mesh + steel ladder belt + bolt + anchor cable ‘ in different regions is proposed. The field monitoring results show that during the removal of coal mining equipment, the surrounding rock deformation of the withdrawal channel is small, the surrounding rock control effect is good, and the equipment is safely and efficiently removed; during the recovery of coal pillars, the surrounding rock deformation of the retained auxiliary withdrawal channel meets the needs of production. The recoverable resources of coal seams will increase by 747,000t, and the economic benefits will increase by 117 million yuan.