三维静载与循环冲击共同作用下组合煤岩体力学特性试验研究

Research on error of single point measurement method for average air velExperimental study on mechanical properties of coal-rock combined body subjected tocombined action of three-dimensional static load and cyclic impactocity in roadway

为进一步研究循环冲击载荷下煤岩体的力学特性,以岩-煤-岩结构试样为研究对象,利用改进后霍普金森压杆试验系统,开展三维静载与循环动态冲击试验,研究冲击入射能及围压对岩-煤-岩结构试样的强度、变形及破坏特征的影响。研究结果表明:相同围压下,总循环次数随冲击入射能的增加而逐渐减少;相同入射能下,总冲击次数随围压的增大而增加;相同围压下,平均应变率随着冲击次数、冲击入射能的增加而逐渐增加;相同入射能下,围压9 MPa时应变率较低且前期增长幅值较为缓慢,围压3 MPa时应变率较高且增长速度较快;峰值应力、变形模量随入射能增加而逐渐递增,随冲击次数增加而逐渐递减;相同入射能下,峰值应力及变形模量随围压的增大而增加;相同围压下,峰值应力与应变率呈幂函数递减,变形模量与应变率呈线性函数递减;循环冲击下,煤岩体破碎程度明显高于单次冲击,破坏主体是煤,破坏形式为剪切-拉伸复合破坏,并且具有明显的率相关性,随着冲击入射能的增加或者围压的减少,煤碎块尺寸较小且块数较多。研究结果可为深部煤岩体动力灾害控制提供理论参考。

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 investigated.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.