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华北上第三系泥灰岩和粘土岩都具有粘粒含量高及“半土半岩”的性质,具有遇水易崩解、膨胀的特性,呈弱~强膨胀潜势。以该区代表性膨胀岩为研究对象,通过X射线衍射实验(XRD)及电镜扫描(SEM)实验和能量光谱测试试验,分析膨胀岩土的造岩矿物的物质组成和微观结构特征。试验结果表明:泥灰岩含有非膨胀矿物方解石、石英、长石以及含有膨胀矿物蒙脱石、高岭土、伊利石等,矿物成分以方解石含量最高在38%~42%之间,其次为蒙脱石,含量在31%~35%之间。粘土岩同样含有以上矿物,但含量与泥灰岩有很大不同,粘土岩中蒙脱石含量35%~40%之间,而方解石的含量只有10%,远低于30%石英的含量。微观结构观察显示,泥灰岩中有少量方解石结晶体,局部富集半结晶的方解石,岩石中的粘土矿物呈层状局部褶曲,有溶蚀边,微细裂缝及孔洞少,而粘土岩中在电镜下未见方解石晶体,粘土矿物有大量褶曲,含大量微细裂缝及孔洞。
The Upper Tertiary marl and clay rocks in North China have the properties of high clay content and semi-earth semi-rock, which have the characteristics of easy disintegration and expansion when water is wet, weak weak strong swelling potential. Taking the representative expansive rock in the area as the research object, the material composition and microstructure characteristics of rock-forming minerals in expansive rock and soil were analyzed by X-ray diffraction (XRD), electron microscopy (SEM) and energy spectrum test. The results show that the marlite contains non-expanded minerals such as calcite, quartz, feldspar, and expansive minerals such as montmorillonite, kaolin and illite. The highest calcite content is between 38% and 42%, followed by montmorillonite Stone, content between 31% ~ 35%. Clay rocks also contain the above minerals, but the content is very different from that of marl, the content of montmorillonite in clay rocks is between 35% and 40%, while the content of calcite is only 10%, well below the content of 30% quartz. The microstructure observation shows that a small amount of calcite crystals are present in the marl and locally enriched semi-crystalline calcites. The clay minerals in the rocks are locally stratified with layers of erosion, fine cracks and fewer holes, while clay rocks are observed under electron microscope No calcite crystals, clay minerals have a large number of folds, with a large number of fine cracks and holes.