Mineral Composition and Microstructure of Completely Decomposed Migmatitic Granite
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摘要: 运用扫描电镜研究不同含水率的风化混合花岗岩微观结构，通过X射线粉晶衍射获得其矿物成分分布，取得了以下新进展：岩样的矿物成分主要为石英、长石、蒙脱石、伊利石和高岭石，石英、长石的平均的含量分别为28.09%、44.26%，黏土矿物中亲水性较强的蒙脱石占比最高，为19.79%；试样显微结构以粗颗粒石英、长石为骨架，以叠片状和碎粒状黏土矿物为充填物形成较为密实的骨架–充填结构；通过对试样的颗粒形态和孔隙分布数据统计分析发现随着含水率升高，细砂粒含量不断增加且颗粒的排列趋于混乱无序，孔隙整体含量及贯通率呈上升趋势，中大孔含量显著增加；由于亲水性黏土矿物吸水诱发膨胀势，导致原始充填结构遭到破坏，密实程度大幅度降低。Abstract: The microstructure of completely decomposed migmatitic granite (CDMG) with different water contents was studied using scanning electron microscopy, and its mineral composition distribution was obtained through X-ray powder diffraction. The results show that the mineral compositions of CDMG are mainly quartz, feldspar, montmorillonite, illite and kaolinite, with the average content of quartz and feldspar being 28.09% and 44.26% respectively. In the clay minerals, montmorillonite with strong hydrophilicity accounts for the highest proportion of 19.79%. The microstructure of the sample is composed of coarse-grained quartz and feldspar as the skeleton, and laminated and crushed clay minerals as the filling material to form a dense skeleton-filling structure. Through the statistical analysis of the particle morphology and pore distribution data of the sample, it is found that with the increase of moisture content, the content of fine sand keeps increasing and the arrangement of particles tends to be chaotic. The pore content and transfixion rate increased, and the content of the macropore increased significantly. The original filling structure was destroyed and the degree of compactness was greatly reduced due to the expansion potential induced by water absorption of hydrophilic clay minerals.
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Key words:
- completely decomposed migmatitic granite /
- mineral composition /
- microstructure /
- particles /
- pore
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表 1 全风化混合花岗岩基本物理性质统计表
天然密度
ρ/(g·cm
−3)最大干密度
ρdmax/(g·cm
−3)含水率
w/%最优含水率
wopt/%相对密度
Gs塑限
wP/%液限
wL/%塑性指数
IP/%渗透系数
k/(cm·s−1)1.89 1.86 19.5 12.3 2.72 20.9 41.3 20.4 6.02×10−5 
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表 2 不同含水率下SEM图像颗粒参数提取结果
含水率/
%颗粒
数量颗粒等效
直径/μm颗粒周长/
μm颗粒总
面积/μm2颗粒面积
占比/%6 582 81.53 80.35 164211.56 73.46 8 535 83.60 82.63 157563.24 70.26 10 463 97.33 90.96 150254.93 65.32 12 455 101.87 107.67 145321.75 62.97 14 412 109.21 118.18 138723.52 57.85
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