不同倾角内蕴裂纹页岩力学特性及破坏过程研究

Mechanical Characteristics and Failure Process of Internal Cracks in Shale with Different Dip Angles

采用真实破裂过程分析软件RFPA2D-Flow,在考虑岩石非均质性和岩石渗流-应力-损伤破裂特性的基础上,对具有不同倾角预制裂纹的页岩力学特性、破坏模式、损伤特征进行模拟分析与讨论。结果表明,预制裂纹对页岩峰值强度有明显弱化作用,弹性模量降低值与裂纹倾角未呈现明显的线性关系;预制裂纹倾角15°、30°、60°时,试件主要破坏模式为小变形的拉伸破坏模式;而倾角45°、75°、90°时,试件以大变形的剪切破坏而失效;裂纹倾角大于45°时裂纹的扩展类型与效果较好。研究结果对改善页岩的水力压裂效果、失稳破坏具有一定参考意义。

With the heterogeneity of the rock and the seepage-stress-damage and fracture characteristics of the rock taken into consideration,the mechanical properties,failure modes,and damage characteristics of the shale with prefabricated cracks of different dip angles were studied by using the real fracture process analysis software RFPA2D-Flow.The simulation analysis and discussion show that the shale specimens with prefabricated cracks have its peak strength obviously weakened,and the decrease of elastic modulus has no obvious linear relationship with the dip angle of cracks.With the dip angle of prefabricated cracks of 15°,30°and 60°,respectively,the main failure mode of specimen is the tensile failure with small deformation.With the dip angle of 45°,75°and 90°,respectively,the specimen becomes ineffective due to shear failure with large deformation.It is found that the prefabricated cracks with the dip angle more than 45°are superior in the type and effect of the crack propagation.This research results can be of certain reference for improving hydraulic fracturing effect and instability failure of shale.