页岩组构对岩石单轴压缩破坏的影响机制研究OA

Laminations,as a key fabric feature of shale,exert a significant control on rock failure behavior and fracture propa-gation,thereby directly influencing the efficient development of shale oil and gas resources.However,conventional macroscopic mechanical experimental methods are strongly affected by the coupled effects of laminations,rock matrix,and natural fractures,making it difficult to isolate and identify the specific influence of lamination structures on the macroscopic mechanical properties and failure mechanisms of shale.To address this issue,this study employs a finite-discrete element method(FDEM)to establish mesoscale mechanical models that incorporate lamination distributions in shale with different lithofacies.These models are used to quantitatively characterize the effects of lamination orientation,thickness,and number on the uniaxial compressive strength,elastic modulus,fracture modes,and fracture morphology of shale.The results indicate that:(1)Hard laminations are the key factor governing shale mechanical properties.After introducing hard laminations into the shale models,the uniaxial compressive strength increases by 17.6%～35.2%,and the elastic modulus increases by 28.0%～39.8%,accompanied by an increase in fracture complexity.(2)As the thickness of horizontal and vertical hard laminations increases from 600 μm to 2000 μm,the elastic mod-ulus and uniaxial compressive strength of shale increase by 19%and 4.8%,respectively,while the proportion of Mode I tensile fractures decreases by up to 70%.When the lamination thickness is≤800 μm,macroscopic shear fractures are formed together with complex tensile branching fractures,whereas when the lamination thickness is≥1500 μm,the number of branching fractures gradually decreases.(3)As the number of hard laminations increases from 5 to 25,the elastic modulus and compressive strength increase by 37.8%and 8.0%,respectively,while the proportion of Mode I tensile fractures decreases by 47.1%,and the number of branching fractures increases,resulting in enhanced fracture complexity.(4)Higher mechanical properties of hard laminations lead to a more pronounced strengthening effect on the shale.The greater the mechanical contrast between the rock matrix and hard laminations,the more significant the impact on macroscopic strength.In addition,with increasing lamination strength,the dominant failure mode gradually transitions from mode I tensile fracture to a mixed mode I-II fracture mode,accompanied by fewer branching fractures.The findings are expected to provide a theoretical basis for an in-depth understanding of the influence mechanism of shale lamination fabric on its macroscopic mechanical properties.