基于轴-径环状分层CT扫描的岩石冻融损伤分析

Freeze-thaw Damage Analysis of Sandstone Based on Fixed-layer Annular Layered and Precise CT Scanning

为研究岩石在冻融循环作用下的破坏损伤机理,结合CT扫描分析法,提出了一种基于轴-径环状分层精确CT扫描的岩石冻融损伤分析方法,将该方法运用于三峡库区砂岩的冻融循环损伤分析,并对各阶段损伤砂岩进行三轴加载试验。结果表明,同一冻融循环次数下,砂岩体积CT值由外向内不断增大,且越靠近外圈层体积CT值减幅越大;随着循环次数增加,损伤变化表现为由外向内的渐进式损伤破坏,在初始损伤阶段,损伤集中于砂岩外层,体积CT值、三轴峰值应力及破坏应变变幅较小;深层损伤阶段,砂岩外部外圈剥落,冻融损伤侵入内部,此时体积CT值、三轴峰值抗压强度及破坏应变变幅明显增大。该方法对岩石冻融损伤分析及冻融灾害防治具有重要的现实意义。

In order to study the failure and damage mechanism of sandstone under the action of freeze-thaw cycle,freeze-thaw cycle tests of sandstone with different cycles in the Three Gorges Reservoir area were carried out,and triaxial loading tests of sandstone were carried out after accurate scanning of the circular stratification of the damaged sandstone at a fixed layer at each stage.The study found that the CT value of sandstone decreases continuously from the outside to the inside under the same number of freeze-thaw cycles,and the smaller the CT value of sandstone is,the larger the decrease amplitude is.As the number of cycles increases,the damage of sandstone under the long-term freezing-thawing cycle can be divided into two stages:the deepening stage of freezing-thawing cycle damage and the stage of surface spalling damage.In the stage of deepening freeze-thaw cycle damage,the sandstone shows that the freeze-thaw damage is concentrated in the outer layer of sandstone,and there is little damage in the interior.The CT value,triaxial peak stress and failure strain vary slightly.In the post-spalling damage stage,the external surface layer of sandstone is spalling and the freeze-thaw damage invades the internal sandstone,while the CT value,the compressive strength of the triaxial peak and the variation of the failure strain are significantly increased.The proposed method has an important realistic significance for analysis of rock freeze-thaw damage and disaster treatment.