基于CT扫描的含非贯通节理3D打印试件破裂规律试验研究

Fracture law of 3D printing specimen with non-consecutive joints based on CT scanning

传统岩石钻孔取芯制备的试件存在同批次内部结构不明确、力学性质差异大等缺点,而插缝法制备试件存在预制节理产状不易控制、精度低、周期长等缺点。3D打印技术克服了传统试件制备方法的不足,但试件存在强度低、塑性高的缺点。采用3D打印技术制作了无节理完整试件A-1-1和非贯通平行四节理试件B-1-1,并进行了真空干燥处理和单轴压缩试验,对试件B-1-1进行了CT扫描试验和内部裂隙三维重构。获得了单轴压缩后该试件的应力-应变曲线、表观破裂模式和试件B-1-1内部裂隙的分布情况。试验结果表明:试件A-1-1的应力-应变曲线与未干燥试件的对比说明真空干燥可提高试件强度减小塑性变形,为3D打印试件在岩石力学领域的适用性研究提供参考;试件A-1-1的应力-应变曲线与煤岩对比,表观破裂模式与中砂岩的对比均相似,说明3D打印试件可用于类似岩石的力学研究;单轴压缩条件下'翼形扁颈漏斗状'破裂模式是使非贯通平行四节理试件失去承载能力的主要破裂模式,其裂隙产生、扩展、贯通演化规律表现为复杂的拉剪组合演化,且内部破裂模式与表观破裂模式存在很大差异,表观破裂模式不能准确表征内部破裂模式。

The rock specimens prepared by traditional rock core drilling method have the disadvantages of unclear internal structures in the same batch and large differences in mechanical properties,and the specimens prepared by inserting joint method have the disadvantages of difficulty in controlling prefabricated joints,low precision and long cycle.3D printing technology overcomes the deficiencies of the traditional specimen preparation methods,but its shortcomings are low strength and high plasticity of the prepared specimens.Non-jointed complete specimen A-1-1 and non-consecutive parallel four-joint specimen B-1-1 were produced using 3D printing technology.Then vacuum drying and uniaxial compression tests were carried out on these specimens.Moreover,CT scanning test and internal fracture 3D reconstruction were performed on specimen B-1-1.We obtained the stress-strain curve,apparent fracture mode of the specimens and internal crack distribution of specimen B-1-1 after uniaxial compression.Experimental results indicate that:the comparison between the stress-strain curves of specimen A-1-1 and the undried specimen shows that the strength and plastic deformation of vacuum-dried specimens have been greatly improved,which provides references for the applicability of 3D printing specimen in rock mechanics field.The stress-strain curve of specimen A-1-1 is similar to that of the rock,and the apparent cracking mode of specimen A-1-1 is similar to that of the medium sandstone,indicating 3D printing specimen can be used in the mechanical study of similar rock.The’wing-shaped flat-necked funnel-shaped’fracture mode is the main failure mode to lose the bearing capacity of the non-consecutive parallel four-joint specimen,and the generation,expansion,and penetration evolution of cracks under uniaxial compression are the combination of the complex tensile-shear group.Besides,the internal fracture mode and apparent fracture mode are different,and the apparent fracture mode cannot accurately characterize the internal fracture mode.