围压条件下粒子冲击破岩裂隙扩展机理研究

Research on crack propagation mechanism of rock impacted by particles under confining pressure

为揭示粒子冲击下围压对岩石裂隙形成及扩展机制的影响,开展了粒子冲击破岩试验和微纳米工业CT(compnted tomography)扫描试验,明确了围压对粒子冲击作用下岩石裂隙扩展特征的影响;并对不同围压条件下的粒子冲击进行数值模拟,分析了岩石的应力场和裂隙场演化过程,揭示了围压影响裂隙扩展的内在机制。结果表明,粒子冲击岩石后,在岩石内部形成破碎区和晶间主裂隙扩展区。压应力导致形成的剪切应力和拉应力是破碎区形成的主要原因,而晶间主裂隙扩展区形成的主要原因是切向衍生拉应力。围压使岩石颗粒间产生预应力,导致切向衍生拉应力需克服颗粒之间的初始压应力才能形成张拉裂隙;围压的增大导致岩石颗粒间剪切裂隙比例和摩擦效应提升,产生相同裂隙数目消耗能量增大,抑制了晶间主裂隙扩展区和破碎区的形成,破碎效果降低。

In order to reveal the influence of confining pressure on the formation and expansion mechanism of rock fissures under particle impact,particle impact rock-breaking experiments and micro-nano industrial compnted tomography(CT)scanning experiments were carried out,which clarified the influence of confining pressure on the characteristics of rock fissure expansion under the action of particle impact.Numerical simulations were carried out on the particle impact under the conditions of different confining pressures,to analyze the evolution process of the rock’s stress and fissure fields,and to reveal the intrinsic mechanism of the confining pressure influencing the expansion of fissures.Results show that after the particles impact the rock,a fracture zone and intergranular main crack propagation zone are formed in the rock.The shear stress and the tensile stress caused by compressive stress are the main reasons for the formation of the fracture zone,while the formation of the intergranular main crack propagation zone is mainly due to tangential derived tensile stress.The confining pressure induces prestress between rock particles such that the derived tensile stress needs to overcome the initial compressive stress between the particles to form tensile fractures.And the increase in the confining pressure leads to increases in the proportion of shear cracks and friction effects between rock particles,resulting in increase in energy consumption for the same number of cracks,which inhibits the formation of the fracture zone and intergranular main crack propagation zone.