In order to explore the influence of different caving thicknesses on the MSS distributionand evolving characteristics of surrounding rocks in unsymmetrical disposal andfully mechanized top-coal caving (FMTC),based on unsymmetrical disposal characteristics,the analyses of numerical simulation,material simulation and in-situ observation weresynthetically applied according to the geological and technical conditions of the 1151(3)working face in Xieqiao Mine.The results show that the stress peak value of the MSS-baseand the ratio of MSS-body height to caving thickness are nonlinear and inverselyproportional to the caving thickness.The MSS-base width,the MSS-body height,theMSS-base distance to working face wall and the rise distance of MSS-base beside coalpillar are nonlinear and directly proportional to the caving thickness.The characteristics ofMSS distribution and its evolving rules of surrounding rocks and the integrated cavingthickness effects are obtained.The investigations will provide lots of theoretic referencesto the surrounding rocks' stability control of the working face and roadway,roadway layout,gas extraction and exploitation,and efficiency of caving,etc.
The change rules of displacement field characteristics of coal seam and tunners surrounding rock were obtained by means of numerical simulation-FLAC^3D and site observation, and according to engineering geology and exploitation technology of 1151 （3） fully mechanized top coal caving （FMTC） face in Xieqiao colliery. The research＇s results show that the top coal displacement on the top of FMTC face is apparently larger than those of the middle and the bottom, the top coal begins to move in the front of the face＇s wall, and the sub-level top coal-rock moves ahead of the low-level top coal-rock, the vertical displacement of top coal-rock increases gradually as the decreasing of distance to face Top coal and overlying strata in vertical direction are always in compressed state in the front of face, then the top coal begins to separate from the overlying strata at the upside of face. The support loading at face is mainly the deformation pressure due to top coal and main roof＇s movement, and it is not suitable for the FMTC face with traditional support design. Surrounding rock movement of the face is of near-field effect, the surrounding rock deformation is acute greatly near to the face, the ideas of supporting design for the tailentry and headentry should be changed from loading control to deformation control.
To make a better understanding of the mechanical characteristics of the surrounding rocks in the tailentry and headentry with different coal seam thickness at fully mechanized top-coal caving face （FMTC face）, the stress transition and displacement around the periphery of the gateways with different coal thicknesses were investigated in details by means of in situ measurement and 3-D numerical simulation. The research shows that the stresses decrease in the two spallings of the headentry and floor at goal with the increase in mining thickness. The roof pressure in the gates does not change obviously with the coal thickness, but the thicker the coal seam is, the farther the maximum stress will apply to the coal rib at the working face. The vertical stress is higher than the horizontal stress at two spallings of the gate, while its horizontal stress is higher than the vertical stress at the roof. The relative displacement between the roof and floor and the two spallings in the gateways increases gradually with the increase in coal seam thickness in a definite range in front of the face. Near the mining face, the stress decreases in the surrounding rock of the gates, while the deformation appears the most intensive. It is proposed that the support concept to the tailentry and headentry should be changed from loading control to deformation control.
