| The safety problem of coal mining has always been the most important part of China’s energy security.It is of great practical significance to study the deformation and rupture law of the combined coal rock mass composed of the impact tendency of coal rock mass and to predict the coal rock power disaster.In this paper,for the coal body and rock mass with similar physical and mechanical properties,by changing the size of the coal block,the coal rock combination body with different contact area with the top and bottom rock is formed,so as to simulate the mechanical structure of laboratory scale coal compression and roof fracture impact rock dynamic disasters.Uniaxial compression and acoustic emission test on the combined coal rock mass,analyze the influence of contact area on the damage type,mechanical parameters and acoustic emission characteristic parameters of the coal rock mass,and determine the corresponding relationship between different damage types of coal rock mass and acoustic emission signal characteristics;according to the magnitude and signal energy calculated in the energy table of acoustic emission parameters,the magnitude calibration method of indoor laboratory scale combined coal rock mass is established.The main research findings are as follows:(1)Under the uniaxial compression conditions,The stress-strain curve of S-1,S-2 and S-3 combination coal rock mass can be divided into compaction stage,elastic stage,non-stable rupture stage and post-peak stage,However,the number of curve stress sharp drop point is different;S-4 stress-strain curve of combined coal rock mass can be divided into rupture stage,compaction stage,second rupture stage,elastic stage,three rupture stage and post-peak stage;Through the test site and stress strain curve distinction: S-1,S-2 combination damage form is coal compression type,The failure form of the S-3 combination is the roof fracture type,The failure form of S-4 combination is that of coal compression and roof fracture.(2)When the combined coal rock mass bears the axial load,as the contact area of the coal unit and the top and the bottom of the rock unit decreases,the energy difference span is large,and the overall energy law is first increased and then reduced.Different damage forms can be simply distinguished by acoustic emission peak frequency: the high frequency is coal compression damage at 150 ～ 180 k Hz,the high frequency is below 150 k Hz and the low frequency is broken at 50-75 k Hz;With the change of the size of the combined coal rock unit,the cumulative ringing count of each channel shows a trend of rise-down-up.(3)With the increase of the contact area with the top and the bottom,the dynamic destruction time,uniaxial compressive strength,elastic modulus and peak energy of the combined coal rock all rise first and then decrease,and the impact energy index decreases first and then increases;the change law of Aemission energy can reflect the destruction law of the internal structure of the combination to some extent.(4)Through the formula of acoustic emission signal energy characterization,the research on the relationship between combined coal mass signal energy and laboratory magnitude provides a new standard for indoor laboratory scale combined coal mass destruction,which can provide theoretical reference for the study of the relationship between indoor scale and engineering scale.The paper has 52 figures,13 tables and 104 references. |
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