Study On Brazilian Splitting Mechanical Response Characteristics Of Coal Samples Under Dynamic And Static Load

With the gradual increase of mining depth,the stress environment around the surrounding rock of coal mine roadway is becoming more and more complex,and the difficulty of roadway support is also greatly improved.Therefore,exploring the deformation and failure characteristics of anchorage coal samples under static and dynamic loads is the basis of stability control and prevention of anchorage support roadway.In order to study the tensile response characteristics of coal samples with and without anchorage,the tensile response characteristics of unanchored Brazilian disc coal samples and anchored Brazilian disc coal samples were tested.The main research contents are as follows:(1)Study on the static physical and mechanical properties of coal samples;(2)Study on tensile response characteristics of anchored coal samples under static load;(3)The tensile response characteristics of anchored coal samples under different rate conditions;(4)Study on tensile response characteristics of anchored coal samples under dynamic load;Using RS-STO2 C rock mass parameter tester,RMT-150 C rock mechanics testing machine,Hopkinson pressure bar(SHPB)test system and other equipment for the above experimental study.The conclusions are as follows:(1)Under uniaxial test conditions,the coal sample shows a typical stress-strain curve,but there is a certain discreteness in the strength data.The failure mode is shear tensile failure,and the main crack runs through the upper and lower surfaces of the coal sample.In triaxial test,the stability of coal samples has been greatly improved compared with uniaxial test,and the failure mode becomes complicated.There are two forms of shear tensile failure and shear failure,and the crushing degree under high confining pressure is less than that under low confining pressure.(2)Under static and dynamic conditions,the strength of anchored coal samples is greater than that of unanchored coal samples.The dynamic strength of both coal samples increases linearly with the increase of strain rate,and the growth rate of tensile strength of anchored coal samples is slightly larger than that of unanchored coal samples.The failure of dynamic loading specimen can be divided into two stages.The load in the complete stage is carried by the coal sample and the bolt,and the stress of the bolt is small.In the crack penetration stage,the load is transmitted through the resin,so that the bolt becomes the main bearing body.(3)The proportion of dissipated energy of anchored and unanchored specimens was positively correlated with the strain rate,and the dissipated energy of anchored specimens increased rapidly.At the same strain rate,the proportion of dissipated energy of anchored coal sample is greater than that of unanchored coal sample;at the same strength,the dissipation energy of the anchored coal sample is greater than that of the unanchored coal sample,and the anchored coal can absorb more energy under the same conditions.(4)Under static loading at different rates,the tensile strength and final splitting energy rate of the two coal samples increase logarithmically with the increase of loading rate,and the anchored coal sample tends to be stable faster.Most of the unanchored coal samples are split into semicircles,and the anchored coal samples are still connected to the bolt by the resin after rupture,forming a whole.