Experimental study on mechanical properties of coal-rock combined body subjected to combined action of three-dimensional static load and cyclic impact
In order to further study the mechanical properties of coal-rock body under the cyclic impact load,taking rock-coal-rock structural specimen as the research object,the three-dimensional static load and cyclic dynamic impact tests were conducted by using an modified Hopkinson Pressure Bar(SHPB)test system,and the influence of impact incident energy and confining pressure on the strength,deformation,and failure characteristics of the rock-coal-rock structural specimens was in-vestigated.The results show that when the confining pressure is constant,the total number of cycles gradually decreases with the increase of impact incident energy.Under the same impact incident energy,the total number of impact increases with the increase of confining pressure.Under the same confining pressure,the average strain rate gradually increases with the increase of impact times and impact incident energy.Under the same incident energy,the strain rate is lower at the confining pressure of 9 MPa with a slower initial growth rate,while it is higher at the confining pressure of 3 MPa with a faster growth rate.The peak stress and deformation modulus gradually increase with the increase of impact incident energy,and decrease gradually with the increase of impact times.Under the same impact incident energy,the peak stress and deformation modulus increase with the increase of confining pressure.When the confining pressure is constant,the peak stress decreases exponentially with the strain rate,while the deformation modulus decreases linearly with the strain rate.The fragmentation degree of coal-rock combined body under cyclic impact is significantly higher than that under single impact.The main body of failure is coal,which is shear-tensile composite failure,and it has obvious rate correlation.With the increase of impact incident energy or the decrease of confining pressure,the size of coal fragments is smaller and the number of blocks is more.The research results can provide a theoretical reference for controlling the dynamic disasters of deep coal-rock body.
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