Evolution law of water inflow in full life cycle of working face in deep buried Inner Mongolia-Shaanxi mining area

The deep buried Inner Mongolia-Shaanxi mining area was newly developed, where the hydrogeological characteristics under the disturbance of coal mining were still unclear. Various types of water damage problems had occurred in the process of infrastructure construction and production. Among them, no research was conducted for the variation characteristics of water inflow during and after mining in working face, which increased the difficulty in the arrangement of underground water drainage system and the work of water prevention and control. In order to find out the evolution law of water inflow in the full life cycle of working face before and after mining, the field research was conducted in terms of the distribution of roof aquifer, the development of water diversion fracture zone and the change of water inflow. The results show that the roof strata of coal seam belongs to fluvial/lacustrine sediments, which are spatially distributed in interbed of aquifer and aquiclude, and the main lithology of aquiclude is mudstone and sandy mudstone. Controlled by the monoclinal structure of Yishan slope in Ordos Basin, the coal-bearing stratum has the lowest elevation in the contiguous area of Inner Mongolia and Shaanxi, and the Jurassic coal measure aquifer in its roof belongs to the regional groundwater stagnation area. Besides, three direct water filled aquifers are developed in the roof strata of coal seam under the action of Mesozoic sedimentary cycle. Among them, Qilizhen sandstone (No. I aquifer) in Zhiluo Formation is 77.4-109.4 m away from the 3-1 coal seam roof, which is characterized by strong water abundance and high water pressure. The water conducting fracture zone has the measured height of 103.4 m at the fracture mining ratio of 18.8, and it is developed to No. I aquifer during the process of working face mining. In the early stage of working face mining, different aquifers are connected with the upward development of water conducting fracture zone, so that the water inflow in mined-out area increases periodically. When the working face is mined to about 300 m, the first peak is presented for the water inflow in the mined-out area. In the middle and late stage of mining, the water conducting fracture zone is developed periodically, resulting in the continuous expansion of damage to the roof aquifer, and the water inflow in the mined-out area still increases by step. Before and after the completion of mining in the working face, the roof water conducting fracture zone in the mined-out area is developed in greatest intensity and range, with the highest water inflow occurring in the mined-out area. After the mining of the working face is completed, the aquiclude is gradually reconstructed under the self-healing cooperation of the argillaceous components in the roof aquiclude, with the width and quantity of water conducting fissures narrowed in width and reduced in number, and thus the water inflow in the mined-out area is attenuated gently (within tens of cubic meters per hour). Mastering the evolution law of water inflow in full life cycle of working face could provide a scientific basis for water prevention and control of underground working face in the deep buried Inner Mongolia-Shaanxi mining area.