温度影响下花岗岩冲击倾向及其微细观机制研究

RESEARCH ON ROCKBURST PRONENESS AND ITS MICROCOSMIC MECHANISM OF GRANITE CONSIDERING TEMPERATURE EFFECT

为考察温度对岩石冲击倾向性的影响,在实时高温(25℃～850℃)和高温热处理后(25℃～1200℃)2种情况下对花岗岩岩样进行单轴压缩和断口电镜扫描试验,结果表明:(1)实时高温下,岩石冲击倾向性随温度的升高存在2个阈值温度,第一阈值温度范围为150℃～250℃,第二阈值温度范围为500℃～600℃。从25℃到第一阈值温度,冲击倾向性指标大幅增大,从强冲击倾向演化为极强冲击倾向;从第一阈值温度到第二阈值温度,冲击倾向性指标略微下降,表现为极强冲击倾向;从第二阈值温度到试验终温,冲击倾向性指标大幅急剧下降,表现为弱冲击倾向或无冲击倾向。(2)高温后冷却情况下,随温度的升高岩样冲击倾向性总体呈逐渐下降趋势,25℃～200℃表现为较强冲击倾向,200℃～800℃表现为中等冲击倾向,800℃后表现为无冲击倾向。(3)5种冲击倾向性指标相比,有效冲击能指数和剩余能量指数较能反映真实的冲击倾向性,其余3种指标因为考虑不全面而产生误差。(4)得到4种典型的应力-应变曲线形态,并分析不同加温方式和温度段与各形态的对应关系。(5)对宏微观破坏形态进行分析,高温后岩样随冲击倾向性的减弱,破坏机制依次为张拉破坏、张剪破坏和剪切破坏,呈现脆性机制向延性机制转变的趋势。

Experiments on granite under uniaxial compression at high temperatures of 25 ℃-850 ℃ and after high temperature 25 ℃-1 200 ℃ were conducted;and the fracture surfaces were observed by scanning electron microscope（SEM） to study the effect of temperature on rockburst proneness.The results show that：（1） Two critical temperatures are found when the rockburst proneness index of samples changes with temperature from 25 ℃ to 850 ℃.The first is from 150 ℃ to 250 ℃;and the second is between 500 ℃ and 600 ℃.The rockburst proneness index increases substantially from the room temperature to the first critical temperature,and it decreases little between the first and the second critical temperatures;above the second critical temperature,it decreases largely.（2） While the samples are refrigerated after high temperature,the rockburst proneness index decreases generally with the temperature increases.The rockburst proneness is strong from 25 ℃ to 200 ℃;it is moderate between 200 ℃ and 800 ℃;above 800℃,it becomes weak.（3） Effective impact energy index and residual energy index are reasonable while the other three indices are unsuitable for incomprehensive information.（4） Four typical stress-strain curves were analyzed to get the relation with the rockburst proneness,and the corresponding relation among the heating mode,the temperature stage and these curves.（5） Based on the macroscopic and microcosmic characteristics of failure samples,it is indicated that the failure mechanism in turn is tension failure,tension-shear failure and shear failure as the rockburst proneness lowers,and it has the tendency that transforms from brittle fracture mechanism at low temperature to ductile fracture mechanism at high temperature.