Experimental study on fracture propagation law of precast rock mass of combined rock mass
In order to solve the problem of the development of coal seam mining fault structure in different rock layers of the roof and floor,the mud-sand composite rock mass with prefabricated three-dimensional fractures was taken as the research object,and the crack propagation and evolution law of the mud-sand composite rock mass was studied by uniaxial compression and triaxial compression tests combined with the method of acoustic emission monitoring.The test results show that the pre-peak stress-strain curves of the three rock masses were relatively similar,and the mud-sand composite rock mass changes due to the change of fractures during the propagation of the layer,and the failure of the upper and lower rock masses was inconsistented,and the post-peak rock mass presents different shapes.The average distribution of the peak intensity of the mud-sand composite rock mass under triaxial loading was 16-18 MPa,and in the acoustic emission monitoring,there were more acoustic emission activities at the fracture position in the middle of the precast mud-sand composite rock mass,and the amplitude reaches the maximum value after failure,which was basically above 70 dB,and then the acoustic emission activity decreases sharply,and the amplitude drops to less than 60 dB.When the mudstone or sandstone with prefabricated fractures reaches the limit,the cracks propagate through the layer,which in turn triggers a new round of acoustic emission activities.When the prefabricated fracture was at the boundary position of the sediment composite rock mass,the prefabricated fracture had broken through the penetration resistance in advance,which will guide the crack to propagate in both directions.The peak acoustic emission ringing count and peak amplitude of the rock samples at the fracture location in the upper and lower parts of the mud-sand composite rock mass were smaller than those in the rock samples at the fracture location in the middle of the mud-sand composite rock mass,and the existence of the fracture in the middle of the mud-sand composite rock mass makes the rock mass structural plane fail,and the deformation and failure are more likely to occur under stress.The research results provide new ideas for the research on the prevention and control of disasters induced by fault tectonic activation and through-bed in coal mining.
rock mechanicscombined rock masstriaxial compressionfracture locationcrack propagationacoustic emission(AE)
张保良、梁秋惠、SHEN Baotang、孟凡震、张巍
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聊城大学 建筑工程学院,山东 聊城 252000
The Commonwealth Scientific and Industrial Research Organisation,Queensland 4069,Australia