煤矿岩巷爆破掘进过程中周边眼对裂纹扩展止裂机理

周边眼在岩巷光面爆破中可以使巷道表面相对光滑完整,同时它对岩体内原生裂纹或爆生裂纹的扩展可能起到止裂的作用。为探究周边眼的止裂作用机理,针对爆破开挖过程中不同间距周边眼对原生裂纹扩展的止裂问题进行了实验及数值模拟研究。实验采用带中心装药孔、预制裂纹(原生裂纹)及两个简化周边眼的有机玻璃圆形试件,观测原生裂纹在周边孔止裂作用下的起裂-扩展-止裂效果。采用AUTODYN软件进行了数值模拟研究,岩石采用线性状态方程(EOS),强度模型为Elastic,失效准则为最大拉应力准则(MMTS),并在扩展路径附近设置观测点,以观测这些点的应力随周边眼间距变化的规律。通过实验及数值模拟结果分析得出:(1)在两周边眼间会产生与裂纹扩展方向垂直的压应力,对裂纹扩展的确能够起到止裂作用;(2)不同的周边眼间距,在周边眼间产生的压应力不同,导致不同的止裂效果;(3)周边眼间距越小,产生的压应力越大,对裂纹扩展的止裂效果越好。

Mechanism of crack arrest by peripheral holes during mine rock roadway excavation under blasting

In smooth blasting at rock roadway the peripheral holes to a certain extent can achieve a relatively smooth and complete section,and also may play a role of crack arrest to rock mass’s native and blasting cracks.In order to explore the crack arrest mechanism of peripheral holes,in this paper,aiming at the crack arrest of the different spacing peripheral holes to native cracks propagation during the explosion excavation process some experiments and numerical simulation study were carried out.Experiments with a center hole charge,pre-existing cracks (native cracks) and a simplified two peripheral holes plexiglass round specimens,were conducted to observe the effect of native crack’s initiation-propagation-arrest under the action of peripheral holes.AUODYN code was applied in the numerical simulation,the linear equation of state (EOS) was applied to the PMMA material.The strength model was elastic and the major principal stress failure criteria was used to predict material status.Along the crack propagation route,a group of target points were designed in order to record the stress histories of those points.Experimental and numerical simulation show that ① between two peripheral holes the compressive stress occurs perpendicular to the direction of crack propagation,the peripheral holes do have the function of crack arrest；② with different peripheral holes spacing,the compressive stress generated between the holes results in different crack arrest effects；③ the smaller the distance,the larger the compressive stress and the crack are more easily arrested.