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In order to study the dynamic evolution law of the pressure relief gas reservoir in the mining of extra-thick coal seams, the 3DEC numerical simulation software was used to analyze the stress and displacement distribution law of the overburden rock caused by mining, and the evolution characteristics of the pressure relief gas reservoir were studied, and the pressure relief gas was proposed. The method of discriminating the location of the reservoir area, and the practice of gas drainage in high-position boreholes at the test working face. The results show that: after the extra-thick coal seam is mined, the height of the overburden caving zone is 49.5 m, and the height of the fracture zone is 104 m. After the key strata in the pressure relief zone on the working face side loses stability, a pressure relief gas reservoir is formed below it. Pressure relief gas reservoir areas are divided into three categories: ①The key layer is in the bent subsidence zone, and the high-level reservoir is formed below it; ②The key layer is in the fracture zone, and the middle-level reservoir is formed under the masonry beam; ③The key layer is in the fracture zone. In the collapse zone, a low-level storage area is formed under the cantilever beam. The shape and area of ​​the reservoir are closely related to the state of the control key layer above. Before the control key layer is broken, the area continues to increase. The shape of the low-level reservoir is rectangular, and the shape of the middle and high-level reservoir is semi-elliptical, expanding to a three-dimensional shape. It is a rectangular cross-section ring body and an elliptical cross-section semi-ellipsoid body; the area decreases rapidly after breaking, and then changes periodically with the pressure of the overlying rock. The low-level reservoir is trapezoidal, the middle-level reservoir is triangular, and the high-level reservoir is shaped like a trapezoid. The shape is a semi-ellipse, and the three-dimensional shape is expanded to a rectangular cross-section ring, a triangular cross-section ring and an elliptical cross-section semi-ellipsoid. The location of the final hole of the high-level borehole was arranged in the range of the middle reservoir area, and the drainage verification was carried out. The maximum drainage concentration of a single hole was 34.5%, the average drainage concentration was 16.8%, and the upper corner gas concentration after drainage was 0.55%, The gas drainage effect is good, indicating that the arrangement of high-level drilling holes according to this method is reasonable.

To explore the evolution law of overburden strata during the mining of huge thick coal seams, an experimental study on the distribution characteristics of the overburden three zones with large mining height was carried out. Based on the geological conditions and mining methods of the huge thick coal seam, a two-dimensional physical similarity simulation experiment under the condition of huge thick coal seam was carried out. The results showed that the height of the overburden strata of the huge thick coal seam in Liuhuanggou（９－１５） 06 working face was 60 m. The horizontal fracture density of the overburden strata in the gob was distributed as a parabola as the propulsion distance increased. Affected by the distribution of strata in the “horizontal three zones”, Delamination of goaf was characterized by “high on both sides and low in the middle”. By calculating physical quantities such as mining overburden subsidence, fissure density, and layer separation and other physical quantities, the formula for determining the height of overburden “three zones” under huge thick coal seams was derived.

The study with completely randomized design on Loess Plateau showed that soil water storage, water consumption, and water profit and loss had a positive correlation with the amount of irrigation. Managed with light, moderate and excessive pruning, soil water storage was increased by 0.2%, 0.5% and 0.9%, soil water consumption was reduced by 0.5%, 2.0% and 2.5%, while soil water profit and loss was increased by 150%, 190% and 210%, respectively. Under treatments with irrigation, covering with grass, mulching with plastic film, and pruning, soil water storage was increased by 4.4%, 1.2%, 1.6% and 0.5%, respectively. Irrigation, moderate pruning, covering with grass, and mulching with plastic film could increase leaf water potential and the angle between little leaf and stem, and excessive pruning could increase the chlorophyll content at most extent (0.27 mg x dm(-2)). The angle between little leaf and stem had a positive correlation with leaf water potential, which could be a reliable, direct and punctual index in evaluating the water condition of walnut and soil, and applied extensively in practice.