Numerical experimental study on the fracture process of shale containing internal prefabricated cracks based on CT scanning with different quartz contents

Abstract

Abstract The quartz content and internal fractures of shale are important factors affecting its mechanical properties and damage modes. To study the mechanical properties of shale under the effect of quartz content and internal cracks, this study used CT scanning technology and digital image processing technology, combined with finite element software to establish a three-dimensional numerical model of shale with different quartz contents and different angles of internal prefabricated cracks, and carried out numerical simulations of Brazilian splitting. Both the quartz content and internal prefabricated cracks in shale can significantly affect the tensile strength of shale. The tensile strength is positively correlated with the quartz content in shale, and tends to increase and then decrease with increasing angle of the internal prefabricated cracks. The quartz content and the internal prefabricated cracks together control the damage of shale, the quartz content increases the damage degree of shale, and the internal prefabricated cracks control the rupture mode of shale, The cracks will have a significant guiding role in crack expansion with increasing angle, and finally show a significant influence on crack expansion from type I to type II. The research results of this paper will play a certain role in promoting the exploitation of shale gas.

Keywords

• Shale
• Quartz
• Internal prefabricated cracks
• CT scan
• 3D numerical modelling
• Brazilian cleavage test