不同应力路径下贵阳红黏土固结不排水试验及微观机理研究

Consolidation undrained test and microscopic mechanism of Guiyang red clay under different stress paths

为揭示贵阳红黏土不同应力路径、固结不排水试验条件下宏观力学特性及微观作用机理,通过分别施加300 kPa、400 kPa、500 kPa不同围压,在增 P、减P、等P 加载路径下,研究其应力-应变关系。结合SEM电镜扫描测试结果,分析了贵阳红黏土颗粒形态和孔隙结构等对宏观力学特性的影响规律。研究结果表明:三种应力路径下贵阳红黏土的应力-应变关系不同,应变速率也具有较大差异,但均表现出不同程度的应变软化现象。不同围压下,红黏土发生剪切破坏的峰值应力与围压呈正相关关系。SEM扫描电镜下,贵阳红黏土内部为片状黏土矿物、少量针状分散矿物及微小不定形物质,按一定的分布规律,进行接触、联结与排列组合形成特殊的微观结构,直接影响着宏观力学特性。

In order to reveal the macroscopic mechanical properties and microscopic mechanism of Guiyang red clay under different stress paths,consolidation undrained tests were carried out.Under “+P”,“-P” and “=P” loading paths,the stress-strain relationship was studied by applying 300 kPa,400 kPa and 500 kPa confining pressure to Guiyang red clay.The influence laws of particle morphology and pore structure on its macroscopic mechanical properties were analyzed by SEM electron microscopy.The results showed that the stress-strain relationship of Guiyang red clay was different under the three stress paths,and the strain rate was also different,but they all showed different degrees of strain softening.At the same time,shear failure of red clay occurred under different confining pressures,and the peak failure stress was positively correlated with the confining pressure.Under the SEM,the flaky clay minerals,a small amount of dispersed acicular minerals and tiny amorphous materials in Guiyang red clay were contacted,connected and arranged following a certain distribution law,forming a special microstructure,which had a great impact on the macroscopic mechanical properties of Guiyang red clay.