煤岩单轴压缩损伤的松弛特性研究

Study on Relaxation Characteristics of Uniaxial Compression Damage of Coal Rock

在较高应力水平下的煤岩流变效应与其损伤状态有关,进而对地下工程的长期稳定产生不利影响。基于Riemann-Lioucille分数阶微积分理论,在整数阶Poynting-Thomson(PTh)流变模型和西原体的基础上引入损伤变量d,通过进行对比构建一个能更好描述煤系软岩的应力松弛模型。通过对煤样分别进行单轴0.27%、0.38%和0.43%轴向应变,应变达到固定应变记录应力松弛曲线,并且对应力松弛后煤样进行CT扫描,通过对CT图像分析得出损伤变量d代入到松弛模型中,对加入损伤前后的西原体模型和整数阶PTh流变模型的松弛曲线和引入损伤西原体松弛曲线与实验曲线进行对比,结果表明整数阶PTh流变模型能更好地描述煤的应力松弛曲线,并且加入损伤变量后提高了描述煤系软岩应力松弛曲线的精度。

The rheological effect of coal rock at higher stress levels is related to its damage state,which in turn adversely affects the long-term stability of underground engineering.Based on the Riemann-Lioucille fractional calculus theory,the damage variable d is introduced on the basis of the integer-order Poynting-Thomson(PTh)rheological model and the western protoplasma,and a stress relaxation model that can better describe the coal soft rock is constructed by comparison.By performing uniaxial 0.27%,0.38%and 0.43%axial strains on the coal samples,respectively,the strain reached the fixed strain recording stress relaxation curve,and the coal samples after stress relaxation were CT scanned,and the damage variable d was substituted into the relaxation model by analyzing the CT image,and the relaxation curves of the Nishihara model and the integer-order PTh rheological model before and after the addition of damage were compared with the experimental curves.The results show that the integer order PTh rheological model can better describe the stress relaxation curve of coal,and the accuracy of describing the stress relaxation curve of soft rock in coal system is improved after adding damage.