Evolution analysis of thick and hard overburden strata and water-conducting fracture zone in double key layer fully mechanized caving face
In order to study the caving characteristics of thick hard overcover rock and the development height of water-conducting fracture zone on the double-key layer,aiming at the development height of"two zones"on the first mining face of a mine and the prevention and control of roof water damage,physical similarity material simulation and RFPA2D-Strata software(strata snalysis edition)numerical simulation method were adopted.Using microseismic monitoring,stress monitoring,acoustic emission monitoring and so on,the development law of roof overburden rock after mining iwas studied,and the height of"two zones"of double-key caving face was determined comprehensively.The results show that the event location of microseismic monitoring and the high density area of energy density distribu-tion would form a water-conducting fracture zone.The total energy and frequency of microseismic events are basically in the high energy region,but the frequency of microseismic events is not necessarily much.When the microseismic event energy value is 108.708 J,a water-conducting fracture zone is formed.The stress variation in goaf region presents an irregular"U"-shaped distribution during subkey layer caving,and the stress behind goaf tends to fluctuate by 5 MPa.On the key layer caving,the stress variation in the goaf region shows a"W"shape distribution,and the stress behind the goaf tends to fluctuate by 6 MPa.With the continuous excavation of the working face,the overlying rock constantly produces acoustic emission failure and then evolves into tensile failure,and develops into bottom-up fracture zone,and finally forms a water-conducting fracture zone.The research results provides a scien-tific basis for the prevention and control of water on the working surface.
double key layermicroseismacoustic emissionwater-conducting fracture zone
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