不同加载速率下含交叉裂隙类岩石力学特性研究

Study on Mechanical Properties of Rocks with Cross Cracks Under Different Loading Rates

对含交叉裂隙类岩石试件开展不同加载速率的单轴压缩试验,研究并分析加载速率对试件力学特性的影响机理,并借助声发射系统分析了其破坏过程。结果表明,试件的峰值应力强度与加载速率呈现正相关性,峰值应力变化幅度随着加载速率的增大表现出先增大后降低的倒“V”形变化;在达到应力峰值前会存在0.15~4.8 min的振铃计数平静期,平静期随加载速率增加逐渐减小,声发射活跃区间由60 min压缩至12 min;试件在低加载速率(δ≤0.2 mm/min)时,声发射振铃计数呈现高频高幅的特点,在高加载速率(δ>0.2 mm/min)时,声发射振铃计数则表现出低频高幅的特点;试件破坏模式为拉-剪混合型破坏,试件处于低加载速率时,以拉伸裂纹破坏为主,在高加载速率时,以剪切裂纹破坏为主。

Uniaxial compression tests with different loading rates were carried out on rock specimens with cross cracks.The influence mechanism of loading rate on the mechanical properties of specimens was studied and analyzed,and the failure process was analyzed by means of acoustic emission system.The results show that the peak stress intensity of the specimen is positively correlated with the loading rate,and the variation range of the peak stress increases first and then decreases with the increase of the loading rate.Before reaching the peak stress,there will be a quiet period of 0.15-4.8min of ringing count,which will gradually decrease with the increase of loading rate,and the active range of acoustic emission will be compressed from 60min to 12min.When the loading rate is low(δ≤0.2mm/min),the acoustic emission ringing count shows the characteristics of high frequency and high amplitude,when the loading rate is high(δ>0.2mm/min),the acoustic emission ringing count shows the characteristics of low frequency and high amplitude.The failure mode of the specimen is tensile-shear mixed failure.When the specimen is at a low loading rate,it is dominated by tensile crack failure,and when the specimen is at a high loading rate,it is dominated by shear crack failure.