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.

In the process of coal mining, when the buried depth is large and the loose layer is thick, the ground subsidence tends to be abnormal, thus causing great damage to the surface ecological environment. In order to reveal the mechanism of mining ground subsidence under ultrathick loose layer, taking 1305 working face of a mine as the background, the law of mining ground subsidence under ultrathick loose layer was analyzed through field measurement. The law of bedrock subsidence is analyzed by similar simulation test, and the role of ultrathick loose layer in bedrock subsidence is quantitatively analyzed. The hydrophobic settlement model of ultrathick loose layer is established by settlement theory calculation, and the law of ground subsidence caused by hydrophobic of ultrathick loose layer is analyzed. The results show that the ground subsidence is mainly composed of bedrock subsidence and hydrophobic settlement of ultrathick loose layer. The maximum ground subsidence measured in the field is 4.201 m, the bedrock surface subsidence obtained by the simulation test of similar materials is 3.552 m, and the subsidence of ultrathick loose layer obtained by hydrophobic settlement analysis is 0.58 m. Adding the subsidence of bedrock surface and the subsidence of ultrathick loose layer, the ground subsidence is 4.132 m. It is in good agreement with the total ground subsidence measured in the field, which verifies the rationality that the ground subsidence mainly includes bedrock subsidence and hydrophobic settlement of ultrathick loose layer.

The surrounding rock control is a tough issue in the roadway with the swelling soft rock. The steel set is an important material for the control of swelling soft rock roadways. However, traditional steel sets failed to prevent the expansive pressure of the soft rock. Based on traditional steel sets, this paper developed a new steel set through both theoretical analysis and numerical simulation. The results showed that the new steel set was the set with the roof beam 1000 mm from the top of the set and the floor beam 400 mm from the bottom end of the set. The maximum deformations of the roof-floor and two sides of the ventilation roadway controlled by the best-improved set at the observation point were 147 mm and 108 mm, respectively. So, the best-improved set can effectively control the surrounding rock of the ventilation roadway. This provides an effective method for the surrounding rock control in extremely soft rock roadways.

The study on influence laws of strata behaviors is the basic guarantee of safety mining for shallow coal seam beneath gully terrain. Taking 3302 mining face of Zhujiamao Coal Mine as the engineering background, the laws of strata behaviors for shallow coal seam mining beneath gully terrain are studied by field detection, theoretical analysis, and numerical simulation. The strata pressure observation and the hydraulic support working resistance show that the dynamic strata behaviors appear violently during mining beneath the gully bottom. The theoretical analysis shows that the rotation and breaking of key stratum beneath gully bottom under nonuniform load is the fundamental cause of strong dynamic strata behaviors. The numerical simulation of overburden movement and fissure development characteristics shows that the strata behaviors beneath the gully bottom are stronger than the strata behaviors beneath other areas. Additionally, according to the laws of dynamic strata behaviors, the safety measures for mining beneath gully bottom are put forward.