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In view of the characteristics of large overburden movement space, strong mining disturbance and difficult to determine the initial pressure step distance of the roof in fully mechanized top-coal caving face with large mining height, the working face 101 of a coal mine is taken as the engineering background, through theoretical analysis, numerical simulation and field measurement methods are used to analyze the roof breakage characteristics and mining pressure appearance law of fully mechanized top-coal caving face with large mining height. Firstly, the mining conditions of the working face are systematically introduced, and the influence of the fully mechanized top-coal caving face with large mining height mining conditions on the roof is analyzed. It is obtained that the direct roof collapses and forms an irregular upper direct roof and a regular lower direct roof. Large massive fine-grained sandstone above the working face are extruded into each other to form a semi-arched "rock-gangue" structure. The UDEC software is used to conduct numerical simulation to verify the initial caving step distance of the direct roof of the top coal, mudstone and fine-grained sandstone, and the broken structure of the roof of the fully mechanized top-coal caving face with large mining height under different propulsion lengths and the plastic zone and stress distribution of the roof are obtained. The research shows that: the first caving step distance of top coal is 14.52 m, the first caving step distance of mudstone is 24.06 m, and the first caving step distance of fine-grained sandstone is 47.83 m; in the special case of failure and instability of "rock-gangue" structure, the reasonable support strength PT of the support shall be no less than 1.13 MPa to meet the requirements of roof support. Through the online monitoring of the working resistance of the hydraulic support through the support resistance monitoring system of the fully mechanized top-coal caving face 101 with large mining height, and through the analysis of the working resistance of the hydraulic support, the breaking characteristics of the roof of the fully mechanized top-coal caving face with large mining height and the regularity of the rock pressure are verified.

With the exposure of these problems of low ductility, easy breakage and high cost of grouting anchor cable, the application of “manila + grouting” full length anchorage technology in the prevention and controlling of coal face failure is more and more widely, the key procedure of which is the selection of manila diameter. Aiming at the difficulty of the choice of reasonable manila diameter, the uniaxial compressive and the wedge shear test of grouting coal samples with manila at different manila diameters were performed using the rock mechanics testing machine. The study shows that: The existence of manila extends the deformation of grouting coal samples and improves the tensile strength of coal samples; The manila has good ductility and high shear strength and the damaged coal body of coal face will not fall down immediately due to the function of manila; The uniaxial compressive strength and residual strength value of coal samples with an appropriate diameter of manila in it can reach the maximum, and the effect of the prevention and controlling of coal face failure is better and the cost is lower. It is concluded that the research result can provide the theory foundation for the “manila + grouting” full length anchorage technology.

Influenced by the dip angle of coal seam, the rib spalling and roof falling of the large-cutting-height panel is prone to occur. The surrounding rock control is a major problem in the mining of large-cutting-height panel with large dip angle. Based on this, ground pressure behavior law in the large-cutting-height panel with large dip angle was studied through laboratory test, numerical simulation and field measurement. The results show that the unidirectional compressive strength and shear strength of mudstone are low, the cohesion and internal friction angle are small, and the joints and cracks are relatively developed, thus, the roof is easy to be destroyed during the mining of working face; influenced by the dip angle of coal seam, the stress concentration degree of the upper and lower ends of the working face is different, and the initial roof weighting interval is about 40 m and the periodic weighting interval is about 20 m; the front abutment peak coefficient pressure of coal face is about 2, and the peak point location is about 15 m away from coal face, and the influence range of abutment pressure is about 40 m, and the strong influence area of abutment pressure is 0–16 m; affected by mining, the cracks in the roof are relatively developed and then broken, which causes roof caving accidents. The research results can provide theoretical basis for surrounding rock control of stope under similar conditions.

In view of the fact that the roof breaking characteristics and overlying strata migration law of close coal seams under repeated mining conditions are not clear, which seriously affects the safety advancing of working face. A large-cutting-height panel in Panjiang of Guizhou Province is used as an example, the roof breaking characteristics and overlying strata migration law under repeated mining are studied using theoretical analysis, numerical simulation and field observation. The research results show that although the roof weighting is not strong in close coal seams mining, there are three kinds of roof weighting phenomena frequently in different overlying strata stratum and the coal face is easy to failure due to the repeated mining; the theoretical formula (5) for determining the support resistance is obtained by establishing the mechanical model and the calculated support resistance of 7200 kN can be determined; compared with the single coal seam mining, the initial weighting interval is smaller and the periodic weighting interval will not change much under the repeated mining; after theoretical analysis and numerical simulation, it can be known that it is necessary to strengthen the control of coal face stability and prevent safety accidents caused by coal face rib spalling in close seams group under repeated mining. The research results provide a theoretical basis for coal seam mining under similar conditions.

Aiming at the problem that the roof broken characteristics and overburden migration law of upper coal seam are not clear due to the disturbance of repeated mining in underlying coal seams, this paper takes a mine of Panjiang mining area as the background, the roof broken characteristics and overburden migration law of upper coal seam under repeated mining of close coal seam group are studied using rock mechanics test, similarity simulation and numerical simulation. The results show that the cracks of coal and rock mass are well developed, the strength is low, and the sensitivity to engineering disturbance is poor; The roof is fragmented due to repeated mining of underlying coal seam, and the rib spalling and roof caving occurs many times; The roof stress value on the coal face is 1.02 MPa, which shows that the roof pressure is not large, and the support selection should focus on preventing the roof caving of end face and the rib spalling of coal face; The pressure peak value point is close to the coal face. Although the roof weighting is frequent, the length of broken rock blocks is relatively small. The initial roof weighting interval is about 30 m, and the periodic weighting interval is about 10 m. The research results can provide basis for surrounding rock control of stope under similar conditions.