| There is abundant coal resource in Guizhou Province that is the largest coal province in southern China.Meanwhile Guizhou Province is the main karst distribution area in China,and karst landforms take up over 70 percentage of its land.Complex terrains,variable distributions of earth surface,underground karsts and water aquifers result in intricacy of the groundwater systems.The yield of water in run-off belts is enormous and its distribution is heterogeneous,that brings great risks and challenges.The thesis takes Xiaotun coalmine as instance,located in Bijie city,northern Guizhou Province.Based on hydrogeological data,field hydrogeology survey was designed and carried out.The Yulongshan limestone is divided into strong run-off zone,fracture filled with water,and void filling zone.Tracing test was used to explore the drainage passage of run-off zone.The lowest elevation of the drainage pipe is located in Yulongshan limestone.According to the time of tracer breakthrough curves,obtained tracer was 45%.The average residence time is 5.75 h.The average speed of tracer migration is 0.065 m/s.The volume of discharge channel system is 862.5 m3.The average Reynolds number is 43668,so the water is absolutely turbulent flow.Borehole statistics around the run-off zone ware analyzed.Mechanical properties of roof rock ware tested.Roof rock is divided into middle hard degree according to the Core RQD value and rock quantitative classification.Fracture evolution process of overburden rock is simulated by RFPA2 D software.It shows that the most height of water flowing failure zone is in T1y1.With the effect of coal mining,the vertical displacement is 62 mm.Stress distribution presents three distinct areas as stress rising areas,stress reduction,original rock stress zone.Micro cracks,pores in argillaceous limestone may increase the permeability coefficient. |
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