高温作用后花岗岩单轴压缩下变形破坏特征研究

本文采用TAW 2000伺服三轴试验机及声发射检测设备,对高温作用后的花岗岩在25~650℃单轴压缩下的声发射特征进行试验研究,分别分析了高温作用后的花岗岩纵波波速、最大强度及振铃计数随时间的变化规律。研究结果表明:花岗岩的纵波波速和最大强度随着温度的升高而下降,当温度超过500℃时,纵波波速和最大强度下降幅度最大,可见花岗岩的阈值温度为500℃左右。高温作用后的花岗岩在加载过程中始终伴随声发射信号,并且与应力-时间曲线具有较好的对应关系,不同温度作用后的花岗岩声发射活动程度不同,温度越高,声发射活动愈强烈。500℃前花岗岩试样主要以劈裂破坏为主,温度达到500℃,花岗岩试样以剪切破坏为主,高温导致花岗岩试样内部结构发生改变,试样内部的裂纹逐渐发生扩展、贯通,最终发生破坏。

DEFORMATION AND FAILURE CHARACTERISTICS OF GRANITE UNDER UNIAXIAL COMPRESSION AFTER HIGH TEMPERATURE

In this paper,the TAW-2000 servo triaxial testing machine and acoustic emission testing equipment are used to analyze the characteristics of granite under uniaxial compression at 25~650℃ after high temperature. The variation rules of longitudinal wave velocity,maximum strength and AE counts with time are analyzed respectively. The results show that the P-wave velocity and the maximum strength of granite decrease with the increase of temperature. When the temperature exceeds 500℃,the P-wave velocity and the maximum strength begin to decrease greatly. It can be observed that the threshold temperature of granite is about 500℃. The acoustic emission signal is always accompanied by the loading process of granite after high temperature action,and has a good corresponding relationship with the stress versus time curve. The acoustic emission activity of granite after different temperature actions is different. The higher the temperature is,the stronger the acoustic emission activity is. Before 500℃,the granite samples show splitting failure,and the temperature reaches 500℃,the granite samples show shear failure. The high temperature causes the internal structure of granite samples to change and the cracks in the samples gradually expand,penetrate,and finally destroy.