The surrounding rock of the roadway under double gobs in the lower coal seams is partially damaged by the mining of the upper coal seam and the stress superimposition of the stepped coal pillars. What is worse, the upper layer of the roof is collapse gangue in double gobs, which makes the anchor cable unable to anchor the reliable bearing layer, so the anchoring performance is weakened. The actual drawing forces of the anchor bolt and anchor cable are only approximately 50 kN and 80 kN, respectively. The roadway develops cracks and large deformations with increasing difficulty in achieving safe ventilation. In view of the above problems, taking the close coal seam mining in the Zhengwen Coal Mine as the engineering background, a theoretical calculation is used to obtain the loading of the step coal pillars and the slip line field distribution of the floor depth. The numerical simulation monitors the stress superimposition of stepped coal pillars and the distribution of elastoplastic areas to effectively evaluate the layout of mining roadways. The numerical simulation also analyzes the effective prestress field distribution of the broken roof and grouting roof anchor cable. A laboratory test was used to monitor the strength of the grouting test block of the broken coal body. Then, we proposed that grouting anchor cable be used to strengthen the weak surface of the roof and block the roof cracks. From on-site measurement, the roadway was seen to be arranged in the lateral stress stabilization area of the stepped coal pillars, the combined support technology of the grouting anchor cable (bolt) + U type steel + a single prop was adopted, the roadway deformation was small, the gas influx was reduced, and the drawing force of the anchor bolt and the anchor cable was increased to approximately 160 kN and 350 kN, respectively. The overall design and control technology of the roadway can meet the site safety and efficient production requirements.

The cross-cut is an important gateway to connect the main roadway and the coal seam. The transportation, the pedestrian and the ventilation of mine could be seriously influenced by floor heave of cross-cut. Aiming at the severe floor heave of +1100 m track cross-cut in Liu Yuan Zi Coal Mine, the cross-cut surrounded with hard roof and soft floor was found. To solve this problem, the bolt-net-shotcrete and 36U-shape steel combined supporting (the original supporting scheme) and the bolt-net-shotcrete and 36U-shape steel round shed combined supporting (the new supporting scheme) respectively were applied to the cross-cut by numerical analysis. The simulation results indicate that the floor heaves is reduced by 57%, and the surrounding rock stress was changed from tension to compression at the bottom and the plastic range decreased and trended to homogenization. Field application results indicat that the cross-cut floor heave can be controlled effectively by bolt-net-shotcrete and 36U-shape steel round shed combined supporting. The conclusions provide a reliable technical scheme for hard roof and soft floor roadway.

To find out the effect of total tailing particle size and grading on the rheological property of filling slurry with high concentration, especially in high intensity, the experiment on the particle size of total tailings was conducted firstly to get the corresponding result. Then, the collapse test of mixed slurry with different cement tailing ratios and different concentrations was carried out to get the corresponding slump value and extension value. Furthermore, the rotational viscometer was applied to test shear stress in the samples with different cement tailing ratios and different concentrations, from which the relevant rheological parameter can be achieved through the Bingham rheological model. Finally, a strength test to mixed slurry block with different cement tailing ratios and different concentrations was conducted (3 days, 7 days, and 28 days); the corresponding intensity values were taken. The experiment result illustrates that with the increase of concentration and cement tailing ratio of the slurry, the collapse degree and extended degree of slurry decreased, while yield stress, plastic viscosity, and strength increased. When the concentration was raised from 70% to 72%, all parameters that characterize good fluidity reduced obviously. As a result, the mixed slurry with a concentration of 70% and cement tailing ratio of 1 : 8 not only meets the requirements of production intensity but also has good mobility and low pipeline wear.