温度作用后花岗岩强度特性及矿物成分变化特征

Strength characteristics and mineral component variations of heat-treated granite

文章基于传统三轴压缩试验,对温度作用后的花岗岩强度特性与破坏形式开展研究,借助X射线衍射仪,从微观角度上分析了强度劣化的相关机理。结果表明:在20~900℃范围内,随温度升高,试样色调变暖;单轴压缩下热处理岩样为对锥形或柱状劈裂破坏,三轴下均为剪切滑移破坏;除了300℃下抗压强度出现增强外,高温作用后花岗岩单轴抗压强度整体呈下降趋势;随温度升高,围压对强度的增强作用变得明显,但这种增强作用难以抵消高温对岩石的损伤劣化效果;在500℃及以下时,岩样主要成分的衍射信息未见明显变化;达到500℃后,在26.5°~27.0°衍射角内石英的衍射峰明显减小,27.5°~28.0°范围内斜长石的衍射峰完全消失。岩样矿物成分改变以及结晶态相变是导致高温作用后岩石力学性质与强度降低的重要原因。

Based on the traditional triaxial compression test,the strength characteristics and failure mode of granite after temperature treatment are studied,and the relevant mechanism of strength degradation is microscopically analyzed with the X-ray diffractometer.The results show that in the range of 20℃900℃,the color of granite specimen becomes warm with the increase of temperature;under the uniaxial compression,the failure mode of heat-treated specimen is conical or splitting failure,while it exhibits shear failure subjected to the triaxial compression.Overall,the uniaxial compressive strength of granite shows a downward trend with increasing temperature except for an accretion at 300℃.As the temperature rises,the effect of confining pressure on the strength enhancement is more obvious.However,this action from confining pressure is difficult to offset the effect of high temperature on rock damage.At temperatures of 500℃and below,there are not significant differences in the diffraction information of the specimen’s main composition.For temperatures above 500℃,the diffraction peak of quartz obviously reduces when the diffraction angle is in the range of 26.5°27.0°,and the diffraction peak of plagioclase completely disappears with the angle ranging from 27.5°to 28.0°.The variations of rock mineral components and crystalline phase-transition are the important cause for the deterioration of mechanical properties and compressive strength of rock after high temperature.