摘要
对石灰岩进行实验室内单轴、三轴压缩试验,得到应力-应变时间序列及岩石损伤破坏实验断口;对不同围压条件下压缩破坏的实验断口进行扫描电镜取像实验,计算石灰岩断口细观尺度下的分数维,以定量追溯其损伤破坏特征。得到围压提高后(<20 MPa)的压缩破坏过程趋向复杂、岩石破坏断口分数维增大的一般规律;当围压增加到岩石单轴抗压强度约2/3时,高围压引发的径向新损伤主导了后期压缩过程,致使最终破坏原因趋于简单,岩石破坏断口分数维降至最低。在连续损伤力学的基本关系式中引入分数维约化指标,构建了描述石灰岩细观破坏特征的分形损伤统计模型。同应力-应变关系的实验结果比较,表明分形损伤理论模型符合实验关系曲线,能理想地反映石灰岩三轴压缩实验结果的应变软化特性,是对岩石细观损伤破坏特征的有益探讨。
The stress-strain time series and rock damage experimental fractures were obtained by laboratory uni-axial and triaxial compressing experiments on limestone. The experimental fractures with the compressive failure of different confining pressures were analyzed by scanning electron microscope imaging experiment. Fractal dimensions in mesoscale space of limestone fractures were calculated to trace the damage feature quantitatively. The general rule that when the confining pressure increases （〈 20 MPa）, the compressive failure process inclines to be complicated and the fractal dimensions of limestone factures increase was obtained. When the confining pressure increased to about 2/3 uni-axial compressive strength of rock, latter compressing process may be controlled by new radial damage caused by high surrounding pressure, which resulted in that the final failure cause tended to be simple and the fractal dimensions of rock damage factures tended to be the minimum. The fractal dimension reduction index was introduced into the basic relation of continuum damage mechanics, and a fractal damage statistical model describing mesoscale failure mechanism of limestone was established. Comparing with the stress-strain test results, it is indicated that the fractal damage theory model is fitted with the experimental relation curve and can ideally reflect the strain softening feature of limestone tri-axial compression test. The proposed model is a valuable discussion for mesoscale failure mechanism of the damaged rock.
出处
《重庆交通大学学报（自然科学版）》
CAS
北大核心
2017年第7期77-82,共6页
Journal of Chongqing Jiaotong University(Natural Science)
基金
国家自然科学基金项目(51004098
51574156)
山东省自然科学基金项目(ZR2014DM019)
关键词
岩土工程
石灰岩
损伤
分形几何学
细观尺度
geotechnical engineering
limestone
damage
fractal geometry
mesoscale
