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【Objective】 Soil water is one of the most important abiotic factors influencing plant growth in arid areas. This paper aims to develop an optimal drip irrigation schedule for alfalfa production in desert farmlands in Northwestern China. 【Method】 The study was based on the HYDRUS-1D model . It compared four irrigation schedules: intensive irrigation (LH-I), moderate intensity irrigation (MH-I), and low intensity irrigation (SM-I). Without irrigation was the control (CK). Each irrigation schedule was associated with five initial volumetric water contents in the 0-20 cm soil layer: 4% (S1), 6% (S2), 8% (S3), 10% (S4) and 12% (S5). Overall, there were 20 combinations. In the simulation for each treatment, we “measured” the time for soil water in the root zone to reach the wilting point, as well as the soil water content at the wilting point. We also measured the time-period during which the soil water content in the root zone remained above the wilting point. These enabled us to find the optimal irrigation schedule. 【Result】 The effect of SM-I and CK on the above criteria was more sensitive to change in the initial soil water content in the top 0-20 cm of soil. The plant roots were able to take up water even without irrigation when the initial soil water content in the 0-20 cm of soil was greater than10%. When the initial soil water content was less than 20%, the majority of irrigated water in the LH-I treatment remained in the topsoil. With an appropriate initial moisture content, the topsoil had a positive effect on retaining the irrigation water from MH-I in the root zone. The retention time of water in the root zone was positively correlated with the topsoil water content in SM-I. The water content in the deep soil was greater in LH-I irrigation than in other treatments. Soil water content remained above the withering point for 5.7 days in MH-I, the longest among all treatments. 【Conclusion】 When initial volumetric water content in the 0-20 cm soil layer was less than 4%, LH-I was optimal, when the initial topsoil water content was higher than 4%, MH-I worked the best.

The dip angle of coal seam is one of the important factors that cause the complexity and particularity of the mining dynamic behavior of the large dip angle stope and induce many disasters and accidents. In order to reveal the influence law of the dip angle of coal seam on the control of surrounding rock and the characteristics of mine pressure in the large dip angle stope, the research method of physical similarity simulation and numerical calculation is adopted. Based on a comprehensive analysis of the features of roof crack and gangue sliding and rolling filling in steeply dipping working faces, a finite element discrete element (FLAC2D-PFC2D) coupling algorithm is used to establish a coupled numerical model of high angle mining areas with different inclinations. The stress distribution of surrounding rock and the inclination effect of gangue filling features in steeply dipping mining areas are studied. The results show the following points. ① Under the action of mining, the stress distribution of the surrounding rock in the roof and floor of the high angle mining area is asymmetric arched. As the dip angle of the coal seam increases, the range of the arched vertical stress release zone and the degree of upward displacement gradually increase. But the range and force value of the horizontal stress release zone gradually decrease. Both vertical and horizontal stresses are prone to stress concentration at the top and bottom of the working face. But the maximum concentrated stress value will decrease with the increase of coal seam inclination angle. The stress magnitude and transmission direction inside the roof and floor of the steeply dipping working face exhibit asymmetric features. As the coal seam dip angle increases, the stress arch height of the working face roof and floor gradually decreases. The transmission direction of surrounding rock stress is mainly towards the mining space, and gradually deviates from the initial approximate vertical direction towards the vertical direction of the working face. ② The roof crack of the working face and the sliding and filling of gangue exhibit temporal and regional evolution features, and exhibit a certain dip angle effect with the change of coal seam dip angle. As the inclination angle of the coal seam increases, the initial breaking position of the direct roof will gradually shift towards the upper area of the working face. At the same time, due to the increased force of gravity along the inclination direction of the working face, the filling degree of the gangue along the inclination direction will be more dense. But the filling length will decrease. As the inclination angle of the coal seam increases, the degree of crack and the range of voids in the high-level rock layers in the upper and middle areas of the working face will also increase. ③ The mechanism of the action of gangue on the surrounding rock in the goaf is mainly reflected in providing lateral stress and vertical support, and is greatly affected by the gravity of gangue, which will show a strong inclination effect with the change of coal seam inclination angle.