盐岩单轴应变率效应与声发射特征试验研究

为了建立声发射参数与盐岩力学破坏机制的关系，进一步揭示盐岩在不同应变率条件下的损伤演化规律，利用声发射技术对加载应变率分别为2×10－3，2×10－4，2×10－5 s－1下的盐岩损伤演化及声发射参数特征进行试验研究。试验发现：(1) 3种应变率加载条件下盐岩的应力–应变曲线变化趋势接近。随着加载应变率的增加，盐岩弹性极限强度略有增加，峰值强度及其对应的应变值略有变化，达到峰值强度所需的时间呈线性减少。(2) 加载速率越慢，岩石破碎越松散，产生的裂纹越多，出现的累计声发射信号数越多。(3) 加载速率越快，声发射频率越高，脆性破坏特征越明显。声发射信号频率变化幅度反映了盐岩在不同应变率条件下裂纹的生成速度和损伤演化过程，而声发射信号累计振铃数则较好地反映盐岩达到峰值强度前应力–应变曲线关系。盐岩自身透光性的变化在一定程度上反映出损伤分布区域和损伤程度。建立基于声发射信号累计振铃数的盐岩损伤演化方程，较好地反映低应变率盐岩损伤演化过程。

EXPERIMENTAL STUDY OF STRAIN RATE EFFECT AND ACOUSTIC EMISSION CHARACTERISTICS OF SALT ROCK UNDER UNIAXIAL COMPRESSION

In order to understand the relationship between acoustic emission(AE) parameters and mechanical failure mechanism of salt rock,and to further reveal the damage evolution law under different loading strain rates,the damage evolution law and AE parameters of salt rock are studied under three kinds of loading strain rates of 2×10-3,2×10-4,2×10-5 s-1 by AE technique.The results show that:(1) The change laws of stress-strain curves of the three kinds of loading strain rates are similar.With the increase of loading rate,the elastic limit strength increases slightly,the peak strength and its corresponding strain value vary slightly,and the time of reaching the peak strength decreases linearly.(2) The slower the loading rate is,the more loosely the rock is crushed,which results in more cracks and more cumulative numbers of AE signal.(3) The faster the loading rate is,the larger the AE frequency is,and the brittle failure characteristic is more evident.The change range of AE signal frequency reflects the crack generation velocity and the damage evolution process of salt rock under different loading strain rates.The AE counts reflect rightly the stress-strain curve of salt rock before peak strength.The change of transmittance of salt rock can reflect the damage distribution regions and damage cumulative ranges to some extent under uniaxial compression.Based on the AE counts,the damage evolution equation is established,which can rightly reflect the evolution of salt rock under low loading strain rate.