动态张拉载荷作用下花岗岩的层裂破坏机理

Spalling fracture mechanism of granite subjected to dynamic tensile loading

在动态载荷作用下岩石可能发生层裂破坏。在动态霍普金森压杆(SHPB)上及4种不同的冲击载荷条件下,开展动态张拉载荷作用下花岗岩的破裂发展和破坏特性研究。岩样破坏后,在破坏表面附近取样并制作薄片,用偏光显微镜观察岩石裂纹的生长模式,并利用扫描电子显微镜(SEM)观察破坏表面的矿物颗粒形貌特征,从而评价岩石矿物特征对载荷和破坏的响应特性。研究结果表明,岩样层裂裂纹数量随着峰值冲击载荷的增加而增多,并且岩石内的石英矿物持续发生大量的晶间断裂;矿物晶体的解理面及其相对于载荷的方向对岩石强度和破裂特性有着至关重要的作用;沿垂直于载荷的矿物晶体解理面进行分离而没有云母矿物平行于载荷的运动是岩石发生层裂破坏所特有的。

Rocks are likely to undergo spalling failure under dynamic loading.The fracture development and rock failure behaviours were investigated during dynamic tensile loading.Tests were conducted with a split-Hopkinson pressure bar(SHPB)in four different impact loading conditions.Thin sections near failure surfaces were also made to evaluate the growth patterns of fractures observed by polarizing microscope.Scanning electron microscopy(SEM)was used to observe mineral grains on failure surfaces and to evaluate their response to loading and failure.The results indicate that the number of spalling cracks increases with increase in peak impact loads and that quartz sustains abundant intergranular fracturing.Cleavage planes and their direction relative to loading play a vital role in rock strength and fracturing.Separation along cleavage planes perpendicular to loading without the movement of micaceous minerals parallel to loading appears to be unique to the rock spalling process.