复杂接触下大理岩球砾碰撞破碎特征

Fracture Characteristics of Marble Balls under Complex Contact Conditions

落石是山区常见的地质灾害之一。为研究块石在复杂接触条件下的运动轨迹,利用改进的分离式霍普金森杆系统开展大理岩球砾冲击试验,研究了球砾碰撞破碎特征,探究了冲击角度、接触面粗糙度等因素对试样破碎的临界速度、破碎特征以及尺寸分布的影响。此外,采用高速摄影机观察试样的破碎特征,并将试样碎片进行筛析,分析试样在不同裂纹发育阶段的碰撞破碎特征。试验结果表明:冲击角度45°≤θ≤90°,尖齿角度α=180°,速度一定时,冲击角度θ越大则试样越容易破裂发育裂纹,试样的破坏率随着冲击角度的增大而增大;冲击角度θ=90°,速度一定时,尖齿高度一定时,尖齿角度α越小,试样越容易破裂发育裂纹,试样最终的破坏率随着尖齿角度α的增加而降低;尖齿角度α一定时,尖齿高度越小,试样越容易破裂发育裂纹,试样最终的破坏率随着尖齿高度的增加而降低。因此,增加接触面尖齿角度或减小冲击角度可以有效降低落石冲击时块石的破碎程度。

Rockfall is one of the common geological disasters in mountainous areas.In order to study the movement trajectories of rock blocks under complex contact conditions,impact tests of marble balls were carried out by using the advanced split Hopkinson pressure bar(SHPB)system.The characteristics of the impact tests of marble balls were studied,and the influence of impact angle,contact surface roughness and other factors on the critical velocity,fracture characteristics and fragment distribution of samples were explored.In addition,a high-speed camera was used to observe the fracture characteristics,and the sample fragments were screened out to analyze the impact fracture characteristics of the samples at different stages of crack development.The experimental results show that when 45°≤θ≤90°,α=180°,the greater the impact angleθis,the more likely the specimen is to crack and develop cracks.The failure rate of the specimens increase with the increase of the impact angleθ.Whenθ=90°and the velocity is constant,the smaller the angleαis,the more likely the specimen is to crack and develop cracks.The final failure rate of the specimens decrease with the increase of the angleα.Whenαis constant,the smaller the tooth height is,the more likely the specimen is to crack and develop cracks.The final failure rate of the specimens decrease with the increase of the tooth height.Therefore,increasingα&reducingθcan effectively reduce the degree of rock breakage.