The Mechanism Of Developmental Behavior Of Water-Conducting Fracture In The Overlying Strata Of Short-Wall Block Mining And The Control Technology In Western China

The majority of coal mines in the western region of China are located in deserts and the edge of deserts,which is an arid and semi-arid area,with characteristic of poor water resources,sparse vegetation,serious desertification and fragile ecological environment.Water resources play an important role in the western region,and are also the key factors to maintain the development of local industry and agriculture and the balance of ecological environment.Mining processes will nonetheless result in movements and damage in the overlying strata,resulting in the formation of waterconducting fractures.Further losses in water resources then occur if the waterconducting fractures develop and come in contact with aquifers or water-rich areas on the surface,which may lead to a series of environmental issues,including losses of vegetation,river runoff,groundwater and increased desertification.These issues have a particularly serious impact on the fragile ecological coal mines in the western region of China.Short-wall block mining(SBM)technology is a kind of independent green mining technology of coal mine in China,which can effectively take into account the safety of coal mining and the protection of water resources.Based on the technology principle and characteristics of SBM,the laboratory test,physical simulation,numerical simulation,mechanics analysis and engineering practice are adopted to carry the research.The mechanism and the development rules of water-conducting fractures during the SBM process are revealed,and the system of short-wall block waterpreserved mining is established for limiting the development of water-conducting fractures,thereby providing an effective,feasible,and environment-friendly solution to the aforementioned issues.The innovation points are as follows:(1)Based on arrangement of working face and spatial structure characteristics of overlying strata failure in SBM,the mechanical model of the superposed beam on the elastic foundation for describing the development of water-conducting fractures of overlying strata in SBM stope is established.The equation of deflection and bending moment of an arbitrary stratum are derived,and the method for judging generation of water-conducting fractures is given,then the mechanism of development and controlling of water-conducting fractures of SBM are revealed.(2)Based on the analysis of the functional relationship between different main controlling factors and the height of water-conducting fracture zone in overlying strata of SBM,the space-time evolution characteristics of overlying strata movement and the development rules of water-conducting fractures in SBM are revealed.Furthermore,a system for predicting the height of water-conducting fracture zone of SBM is established,which provides a theoretical basis for the accurate prediction of the height of water-conducting fracture zone.(3)According to different mining geological conditions,giving the discriminant method of the low-failure aquifuge,the high-safety aquifuge and the median-attenuated aquifuge,then the short-wall block water-preserved mining system and evaluation mechanism are established,which combined with development rules of waterconducting fractures and the method for predicting the height of water-conducting fracture zone in SBM.The dual objectives of protecting water resources and improving the recovery rate of coal have been achieved.(4)Engineering design method of short-wall block water-preserved mining is proposed by the result of comprehensive theory research,which can optimized the key parameters of working face and production system in SBM.Then the monitor and feedback system of height of water-conducting fracture zone & surrouding rock stability is established.This finding is significant for addressing water conservation issues and promoting green mining practices.