基于CT扫描的饱和破碎灰岩侧限压缩下微观结构演化特征

Microstructure evolution of saturated crushed limestone under lateral confined compression based on CT test

为探求破碎岩体在压实过程中微观结构的演化规律,对饱和破碎灰岩进行侧向受限压缩试验,进行了试样内部微观结构形态的显微CT扫描;定量描述了压实过程中灰岩颗粒的破碎程度,分析了孔隙度与颗粒平均粒径之间的关系;基于图像处理技术,定量分析了颗粒表面形貌的演化规律。试验结果表明:在饱和破碎灰岩压实过程中,颗粒破碎现象普遍存在,试样内部孔隙被压缩或充填,孔隙间连通性变弱。颗粒的初始配比影响试样孔隙度,相同轴向应力下,随着Talbot指数的增大,试样孔隙度单调增大。孔隙度与颗粒平均粒径之间满足线性关系,孔隙度的变化可以作为描述颗粒破碎程度的一个有效参量。随着轴向应力的增大,颗粒的圆形度单调减小,颗粒表面形貌越来越规则,圆形度与轴向应力之间满足指数关系。该研究有助于深入了解破碎岩体的变形机制。

Lateral confined compression tests for saturated crushed limestone were conducted to study the evolution of the microstructure in crushed rock masses. Micro-CT system was used to observe the microstructure of the samples.Based on the average particle size,the particle crushing state of the saturated crushed limestone under compaction was obtained quantitatively,and the relationship between porosity and average particle size was analyzed. Using image technology,the evolution of the particle shapes was studied quantitatively. The experimental results indicate that during compaction,particle crushing is pervasive,the pores in samples are compressed and filled with fine particles,and the connectivity between pores become worse. The initial gradation influences the porosity of samples. Under same axial stress,the porosity increases with an increase in Talbot exponent. The relationship between the porosity and the average particle size is linear,and the porosity can be used to describe the crushing state of the samples quantitatively. With the increase of axial stress,the circularity of the particles decreases monotonously,the shapes of the particles are moreregular,the relationship between circularity and axial stress can be fitted by an exponential function. The study is helpful for a better understanding of deformation mechanism of crushed rock mass.