中生代砂岩细观结构对强度和能量耗散的影响

Effect of mesozoic sandstone meso structure on strength and energy dissipation characteristic

对取自东北部和西部侏罗白垩系煤矿中粒砂岩进行镜下观察,对比其矿物颗粒,胶结成分和结晶程度上的异同点,进行了三轴压缩试验和循环加载声发射试验,分析东北部和西部砂岩的强度和能量耗散特征,并用Kaiser效应和加卸载响应比理论研究了循环加载中的声发射规律。试验表明:以钙质胶结为主的东北部砂岩在Mohr-Coulomb准则下承载能力高于以钙泥质胶结为主的西部砂岩,随着压力的增大,耗散能所占比例呈现迅速降低、稳定、缓慢升高的趋势,且同等应力水平下东北部砂岩耗散能低于西部砂岩,Kaiser效应往往出现在低应力的弹性阶段,且在东北部砂岩中出现的频率和持续阶段要高于西部砂岩,加卸载响应比则出现急剧降低、缓慢平稳下降的趋势,在强度峰值点达到最小值,且东北部砂岩的加卸载响应比低于西部砂岩。东北部和西部砂岩的胶结物中泥质含量和重结晶成岩程度是产生上述力学性质和能量耗散特征差异的根本原因。

The mesozoic medium particle sandstone slices of northeastern and western coal mines were observed under microscope,and the mineral particles,cementing composition and crystallization degree were analyzed for the following triaxial cell loading and cyclic loading acoustic emission（ AE） experiments. The variation laws of strength criterion,dissipated energy,Kaiser effect and load/unload response ratio（ LURR） were discussed. The results show that the northeastern calcareous cemented sandstones show a higher strength than that of the western calcareous argillaceous cemented specimens by the Mohr-Coulomb criterion. At the equal stress level the northeastern sandstone elastic energy is higher and the dissipated energy is lower comparing with western sandstone. During the cyclic loading,the Kaiser effect usually occurs at the elastic stage within low stress level,and the northeastern specimens contains more Kaiser points than that of western specimens. As the stress increases,the LURR decreases sharply at low stress stage,then declines steadily,and reaches minimum at the peak strength,moreover the northeastern sandstone LURR is lower thanthat of the western specimens. The differences of the mechanics and energy dissipation can be ascribed to the diversity of cementing composition and crystallization lithogenesis degree.