Aiming at the problem that it is difficult to popularize in Guizhou mining area due to high filling cost, taking 11071 working face of Panzhihua Coal Mine in Liupanshui as the research background, the idea and technology of strip interval filling mining are put forward. Through theoretical analysis and mechanical tests, the reasonable range of strip spacing distance and mechanical parameters of filling body were obtained. The FLAC3D simulation software is used to analyze the stress field, displacement field, and plastic zone of five kinds of design schemes, and the UDEC simulation software is used to carry out the filling mining of No.7 coal seam. The results show that the strip interval filling mining technology regards the empty roof area as a controllable underground spatial structure, and the single spatial stress field changes little. The load on the immediate roof is gradually transferred from the top of the empty roof area to the top of the filling body. The “filling body-direct roof” structure improves the self-bearing capacity of the immediate roof, and the overlying surrounding rock migration is controlled. With the increase of mining depth, it gradually tends to the original rock stress, and the control effect on surface subsidence is more significant. Finally, “filling 3 m interval 3 m” is determined as the optimal filling scheme. In the process of simulated filling mining, the peak stress in the stress concentration area of the front coal wall shows a trend of “increase-decrease-increase,” and the peak stress curve of the immediate roof in the middle of the stope changes from “increase-decrease ‘trend to’ increase-decrease-increase-decrease” trend. The rock layer near the immediate roof is in a stress concentration state in the coal wall area on both sides, and the middle part is not obvious.
The cyclic freezing-thawing action in cold regions leads to the deterioration of rock damage, resulting in local damage and further threatening the safety of engineering. In order to study the degradation characteristics of green sandstone and yellow sandstone under freeze-thaw cycles from macroscopic and microscopic aspects, the sandstone of a mining area in Inner Mongolia was used as experimental material. The freeze-thaw cycles were divided into 20 times, 30 times, and 40 times. NMR images and mechanical test results of two different rock samples were analyzed by binarization, NMR, and mechanical test. The test results show that, except that the mass change is less than that of yellow sandstone, the physical index degradation degree of green sandstone is higher than that of yellow sandstone, and the frost resistance is less than that of yellow sandstone. The change of acoustic emission event rate of green sandstone is mainly in the elastic deformation stage and stable crack propagation stage, and the change of acoustic emission event rate of yellow sandstone is concentrated in the crack closure stage. In the loading process, the energy release trends of the two sandstones are similar; the 30 freeze-thaw cycles are the boundary of brittle-plastic transformation of green sandstone, and the increase of cumulative energy is the most obvious. The research results provide a theoretical basis for studying the rock failure mechanism and improving the stability of rock engineering in cold regions.
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