砂岩断裂及其亚临界断裂的力学行为和细观机制

Mesomechanism of fracture process and subcritical fracture in sandstone

通过三点弯曲的SEM试验,详细研究了砂岩断裂的力学特征和细观机制。结果表明:砂岩断裂是一个复杂的过程,它不但与砂岩的物理成分、微缺陷等有关,还与砂岩中碎屑颗粒的分布密切相关,存在明显的亚临界断裂。亚临界断裂裂纹和断裂主裂纹形态相似。亚临界断裂裂纹较多的样品呈现延性断裂破坏的特征,而亚临界断裂裂纹较少的样品则呈现脆性断裂破坏的现象。

The morphology of sandstone fracture main crack and subcritical fracture crack （that growth due to stress concentration but not turn into fracture main crack） in mesoscale level have been systematically investigated through the three-point bending fracture test with scanning electron microscope （SEM）. It is shown that the fracture of sandstone behaved complicatedly, and correlated with not only the composition of sandstone binding material but also the distribution of sandstone fragmentary particle. Furthermore, there give birth to many subcritical fracture cracks in the fracture process. The morphology of fracture main crack and suhcritical fracture crack is similar. Ductile fracture has been taken place if the specimen has many subcritical fracture cracks in the fracture process zone. Contrary that brittle fracture will be taken place.