高温热处理对花岗岩巴西劈裂裂纹萌生与破坏特征的影响

Effect of High Temperature Heat Treatment on Initiation and Failure Characteristics of Brazilian Crack in Granite

为研究高温对劈裂裂纹产生、扩展和贯通过程的影响,对25~1000℃热处理后的花岗岩开展巴西劈裂实验,采用数字图像相关技术(DigitalImagineCorrelation,DIC)跟踪分析了试样在劈裂过程中的主应变场演化。研究结果表明:1)随着热处理温度升高,花岗岩劈裂破坏后宏观断口处弯曲程度加剧,破坏模式由拉伸破坏变为拉剪混合破坏。2)不同高温劈裂条件下,花岗岩总体经历了弹性-塑性-破坏阶段。25℃时,试样发生脆性破坏,塑性变形和破坏阶段极短;100~500℃时,主应变在塑性阶段内明显累积,破坏阶段很短,仍为脆性断裂;600~1000℃时,破坏阶段明显,失效模式转变为延性破坏。3)随着温度升高,花岗岩延性逐渐增大,端部效应减弱,弹塑性过渡点PE-F相应的荷载水平线性降低。

In order to study the influence of high temperature on crack generation,propagation and through-process,the Brazilian splitting test was carried out on granite treated at 25–1000℃,and the evo-lution of the principal strain field of the sample in the splitting process was tracked and analyzed by digital image correlation(DIC),and the results showed that:1)With the heat treatment temperature increases,the degree of bending at the macroscopic fault after granite splitting failure intensifies,and the failure mode changes from tensile failure to tensile and shear mixed failure.2)Under different high-temperature splitting conditions,granite generally underwent the elastic-plastic-failure stage.At 25℃,the specimen undergoes brittle failure,plastic deformation and failure stage is extremely short;at 100–500℃,the main strain accumulates significantly in the plastic stage,and the failure stage is very short,and it is still brittle fracture;at 600–1000℃,the failure stage is obvious,and the failure mode changes to ductile failure.3)With the increase of temperature,the brittleness of granite weakens,the ductility of granite gradually enhances,the Y-shaped rupture disappears,the corresponding load level of PE-F at the elastoplastic tran-sition point decreases linearly.