黄土高原马兰黄土微结构特征及湿陷机理  

Characteristics of Microstructure and Collapsible Mechanism of Malan Loess in Loess Plateau,China

作　　者：魏亚妮 范文[1,2] 麻广林 WEI Ya-ni;FAN Wen;MA Guang-lin(School of Geological Engineering and Geomatics,Chang'an University,Xi'an 710054,Shaanxi,China;China Electronic Research Institute of Engineering Investigations and Design,Xi'an 710054,Shaanxi,China)

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054 [2]信息产业部电子综合勘察研究院,陕西西安710054

出　　处：《地球科学与环境学报》2022年第4期581-592,共12页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(42002285,41630634)。

摘　　要：黄土微结构的认识和刻画在研究黄土宏观湿陷变形行为以及揭示其内在机理方面扮演不可或缺的角色。选取黄土高原甘肃兰州、庆阳以及陕西横山、洛川、泾阳等5个地区马兰黄土试样,通过开展室内湿陷试验、微米级CT扫描以及压汞测试,厘清不同地区马兰黄土的微结构特征,分析对比湿陷过程中孔隙分布的变化规律,以此探讨马兰黄土的湿陷机理。结果表明:5个地区马兰黄土湿陷性在区域上整体表现为从西北向东南逐渐减弱的趋势;兰州和横山地区马兰黄土的微结构以单粒架空/镶嵌为主,前者颗粒排列疏松,后者排列相对密实;庆阳、洛川和泾阳地区马兰黄土中黏粒支托结构相对明显;黄土湿陷过程中,孔径在3~60μm区间的粒间孔隙体积减小幅度最大,为湿陷提供主要空间。5组黄土微结构特征及湿陷前后孔隙分布变化表明,黄土湿陷与否取决于两方面因素:一是黄土内部需有发生湿陷的空间,孔隙分布特征对湿陷性强弱有重要影响,集中分布的粒间孔隙有利于湿陷发生;二是需有能够引起湿陷的动力因素,桥接形式的黏粒发生水化膨胀是引起颗粒滑移进而发生湿陷的重要动力之一。Characterization of loess microstructure plays an important role in the research of collapse behavior and mechanism.Laboratory collapse tests,micro X-ray CT scanning and mercury intrusion porosimetry were conducted on Malan loess located in Lanzhou and Qingyang areas of Gansu,and Hengshan,Luochuan and Jingyang areas of Shaanxi,to characterize their microstructure,analyze the collapse differences and variations,and finally discuss collapse mechanism.The results show that Malan loess collapsibility decreases from northwest to southeast in Loess Plateau.Malan loess in Lanzhou and Hengshan areas both show interlocking and overhead structures with inter-particle pores,while the particles packing is loose in the former and dense in the latter.Clays buttress of loess is apparent in Qingyang,Luochuan and Jingyang areas,which determines the distribution of intra-particle pores.In the process of collapse,the pores in the diameters of 3 to 60μm present significant decrease in volume,which provide main space for loess collapse.Microstructures and pore size distribution variations of five samples of loess collected from Lanzhou,Qingyang,Hengshan,Luochuan and Jingyang areas,indicate that two factors determine loess collapse.One is that there is sufficient space in loess provided for collapse,pore size distribution has important influence on the collapsible degree,the loess with intensive inter-particle pores is most likely to collapse;the another is that there are forces in loess which can induce collapse,hydration swelling of clay bridge between particles can be considered as an important inducement for collapse.

关 键 词：马兰黄土 湿陷性 微结构 孔隙分布 黏粒 湿陷机理 CT扫描 黄土高原 

分 类 号：P642.13[天文地球—工程地质学]