| With the increasing of mining depth in China,the threat of high pressure karst fissure water from ordovician system to the safe mining of lower group coal seam becomes larger.According to statistics,about 80%of floor water inrush accidents are related to faults,and the hidden faults are the main factors that cause floor water inrush.Therefore,starting from the recent case analysis of coal seam floor water inrush in the southern coal field in North China,this paper uses a combination of theoretical analysis,field measurement,indoor test,similar simulation and numerical simulation to solve the difficult problem of coal seam floor hidden fault inrush,and then systematically studies the process of coal seam bottom plate failure and progressive guidance cooperative water intrusion.This paper mainly completes the following research content:(1)Based on the analysis of water inrush data from Jiaozuo,Zhengzhou and Yongcheng mining areas,which suffered serious water disaster in Henan Province,it is concluded that under the combined action of mining stress and confined water,the necessary and sufficient conditions for progressive uplift are hydraulic pressure and fracture,the place where the floor of coal seam has the phenomenon of guiding is the place where the structure develops,and also the place where the mechanical property is weak,the water-inrush and the quantity of water inrush are directly determined by the water-rich property of Karst Aquifer and the water pressure.Based on the analysis of recent floor water inrush cases,the progressive uplift phenomenon of the concealed floor structure under the combined action of water pressure and ground pressure is expounded,the possibility of the synergetic water inrush phenomenon between floor mining failure and progressive lifting is confirmed.(2)Based on the linear elastic fracture mechanics and the theory of progressive lifting,a mechanical model of synergetic water inrush from the failure of stope floor and progressive lifting is established,and the evaluation criterion of synergetic water inrush from floor and progressive lifting is proposed.Using the Stress intensity factor at the upper end of the hidden fault in the floor,under the influence of mining,the stress concentration at the tip of the fault plane increases and the Stress intensity factor increases,the stress changes at the tip of the fault plane repeat the above-mentioned,the height of the guide rises again,the effective water-resisting thickness decreases,and the failure depth of the floor increases,and the water inrush occurs when it connects with the height of guide.The analytical formula of the critical mechanics of water inrush and the minimum safe distance from the fault to the failure zone of the floor are derived.(3)Based on the mining of No.2-1 coal seam in Zhaogu No.1 coal mine in Jiaozuo Mining area,a set point dynamic monitoring system of coordinated water inrush was independently developed,a material-like model of mining failure of floor with hidden faults and progressive lifting is designed,which shows that the progressive development of mining failure and progressive lifting height is the key factor of water inrush from floor.The simulation results show that with the advance of the working face,the progressive uplift process of the concealed fault has experienced four stages:natural uplift stage,progressive uplift stage,enhanced uplift stage and breakthrough stage,when the peak value of mining stress unloading appears,the progressive lift degree is strengthened and the water quantity is increased,the unloading degree of the floor rock mass reaches the peak value synchronously with the progressive lifting strength and the water output of the dynamic monitoring pipe.(4)The dynamic development process of floor fracture propagation and water inrush from concealed fault is systematically studied by FLAC3D numerical simulation.With the excavation of the working face,the seepage field around the hidden fault is gradually connected with the plastic failure field in front of the working face under the interaction of water and rock,and the dangerous channel of Water Inrush from the fault is gradually formed,the evolution process of stress field and seepage field in the water inrush path of floor,i.e.the gradual coupling process of plastic failure field and seepage field of surrounding rock.It is revealed that the mechanism of The in-situ tension fracture of the underlying fault floor?Extension and hydraulic tracking delivery?Development of ascending zone in situ?Communication between mining failure zone and progressive lifting zone? Mechanism of synergetic water inrush from floor rock fracture and progressive lifting.The results of simulation are similar and consistent with those of similar simulation.(5)Using the high-precision micro-seismic monitoring technology,the continuous dynamic monitoring of the bottom plate of the 16001 working surface of Zhaogu No.1Mine,the range of crack development,and the process of progressive leading water surge of hidden faults,the space-time distribution of microseismic events of bottom plate failure and progressive leading joint water surge are obtained.This paper proves the rationality of the mechanism of floor failure and progressive guidance and synergistic water intrusion,and forms a set of field monitoring technology system for coal seam floor water intrusion prediction,which has important practical significance and broad application prospects.Figure[87]table[13]reference[198]... |
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