黄土湿陷微观机理研究现状及发展趋势

Research progress and prospect of loess collapsible mechanism in micro-level

黄土特有的湿陷性使其具有遇水软化和工程扰动的强致灾特性,从根本上认清黄土的湿陷机理,是解决黄土地区地质灾害及工程地质问题的迫切需求。文章搜集整理黄土湿陷机理方面的研究成果,从黄土的胶结物组成、性质及胶结方式,微结构特征和颗粒间作用力等三个方面归纳总结黄土湿陷微观机理的研究现状。通过实例分析初步探讨了延安新区马兰黄土的湿陷机理。结果表明:(1)黄土的微结构特征回答了黄土“如何湿陷”的问题,颗粒间胶结物组成、性质及胶结方式以及颗粒间作用力直接回答了黄土“为何湿陷”的问题;(2)延安新区马兰黄土中大于23μm的镶嵌孔隙为湿陷提供主要空间,黏土胶结的水化膨胀是引起颗粒间强度降低、发生湿陷的主要原因之一;(3)目前黄土湿陷机理研究仍不够系统、深入,一些湿陷现象仍缺乏合理的解释,由此认为高精度的三维表征是黄土微结构研究的基础,水、力作用下微结构的高精度动态演化观测,以及黄土中胶结物的组成、性质及胶结方式的精细化研究,是理解黄土“如何湿陷”和“为何湿陷”的重要途径;(4)在此基础上,建立不同类型黄土的微观信息数据库,通过数理分析及人工智能等方法,明确单一要素对宏观湿陷行为的控制作用,同时构建考虑主要微观要素的理论模型,预测不同条件下的宏观湿陷行为。以上研究将对深入理解黄土湿陷机理、建立黄土湿陷微观要素与宏观行为的定量联系具有重要理论意义和实际应用价值。

Loess is a typical soil with collapsibility featured with strength reduction under wetting and disasters induced by disturbance.Recognizing the mechanism of loess collapse is urgent demand for solving geological disasters and engineering problems.This paper reviews the achievements related to collapsible mechanism in micro-level,and summarizes the research progress.The Malan loess in Yan’an New District is taken as an example,and the collapsible mechanism is analyzed and discussed.The results show that(1)loess microstructure feature can answer the question of“how loess collapse”,while components,properties and bonding modes of cementations as well as forces among particles can explain“why loess collapse”.(2)The pores larger than 23μm provide main space for collapse of the Malan loess in Yan’an New District,and the hydration swelling of clay cementation is one of the main causes for particle movement and collapse.(3)However,research on collapse mechanism is still unclear,some collapse behavior cannot be fully explained.The research interests related to collapsible mechanism are also suggested in this study.It is considered that microstructure characterization in 3D space is the basis of loess microstructure research.Dynamic observation of microstructure with high resolution under loading and wetting,and detail investigation of the components and properties of cementations as well as the bonding modes,are effective ways to interpret“how loess collapse”and“why loess collapse”.(4)The database of various types of loess containing all micro information should be established to definite the influence of single factor on collapse behavior,via mathematical analysis and artificial intelligence.The theoretical model involving major factors should be simultaneously established to predict collapse behavior under different conditions.This work will be of great theoretical and practical significance to interpret loess collapse mechanism and establish quantitative relationship between micro factors and macro behaviors.