高温后花岗岩冲击破坏行为及波动特性研究

 采用SRM–5N超声检测分析仪和高温分离式霍普森压杆(SHPB)系统装置，分别对不同高温后花岗岩的波动特性和动态力学特性进行试验研究，分析不同温度条件对花岗岩纵波波速、波形频谱的影响，研究高温后花岗岩的动态抗压强度、峰值应变以及冲击破碎形态的变化情况。试验升温等级设为25 ℃，100 ℃，200 ℃，400 ℃，600 ℃，800℃，1 000 ℃七个等级，升温速度为10 ℃/min。试验结果表明：(1) 随着温度的增高，花岗岩试样的热损伤总体上呈逐渐增大趋势。但是100 ℃之前热损伤有所降低，出现负的热损伤，随后热损伤不断增加，直到600 ℃以后热损伤增幅开始变缓。(2) 随着温度的升高，试样的动态抗压强度总体减小，峰值应变总体增大；但是在110 ℃左右，抗压强度有所增强，峰值应变有所减小；600 ℃之后抗压强度和峰值应变分别显著减小和增大。(3) 推断110 ℃左右为花岗岩一个阈值温度，在这个温度之前，温度的对花岗岩产生负损伤，花岗岩强度增强；推断600 ℃～800 ℃范围内存在为花岗岩另一个阈值温度，超过这个温度花岗岩的力学性能发生显著变化。该方法和成果可为岩体工程施工、防火设计以及火灾后评估修复提供一定参考价值。

RESEARCH ON IMPACTING FAILURE BEHAVIOR AND FLUCTUATION CHARACTERISTICS OF GRANITE EXPOSED TO HIGH TEMPERATURE

The behavior impacting failure and dynamic mechanical properties of granite exposed to high temperature have been researched with high-temperature split Hopskinson pressure bar(SHPB) system and ultrasonic detector SRM–5N. The scope of this research includes the variation of longitudinal wave velocity，waveform，dynamic compressive strength and peak stress with the temperature. The temperature varies in the range of 25 ℃，100 ℃，200 ℃，400 ℃，600 ℃，800 ℃，1 000 ℃，and the heating velocity is 10 ℃/min. The results are as follow：(1) Generally speaking，the thermal damage of granite gradually raises with the temperature increasing. But it decreases before 100 ℃，Then enhancement of thermal damage is not drop slowly until exposed to 600 ℃. (2) As a whole，the dynamic compressive strength of granite is diminution and peak strain is enlarge when the temperature is enhanced，but it is opposition with them before 110 ℃. And dynamic compressive strength is obviously reductive and peak strain is obviously enhancive after 600 ℃. (3) It is suggested that 110 ℃ is a temperature threshold of granite，before this temperature，the thermal damage of granite is minus，the dynamic compressive strength decreases. And suggested another temperature threshold is 600 ℃– 800 ℃，the dynamic mechanical properties of granite changed obviously beyond this temperature. The research method and conclusions can provide references for rock project construction and fireproofing designs.