不同黏粒含量对黄土渗透系数影响的试验研究

Experimental Study on Permeability Coefficient of Loess with Different Clay Content

[目的]开展不同黏粒含量对黄土渗透系数影响的试验研究,揭示黏粒含量对渗透系数的影响及其微观机理,为黄土及其渗透性相关的理论与工程实践提供科学依据。[方法]通过自制负压湿筛装置筛取不同黏粒含量的黄土试样,利用激光粒度仪对土样的黏粒含量进行跟踪测定,采用静压法将不同黏粒含量的黄土试样制成天然干密度水平下的不同含水率试样进行饱和渗透试验。[结果]黏粒含量对黄土渗透性能有较大影响,在同一含水率条件下,随黏粒含量的增多,黄土的渗透性逐渐降低,渗透系数与黏粒含量呈指数函数负相关关系;在黏粒含量一定时,渗透系数随着初始含水率的增加而减小,呈指数函数负相关关系;SEM分析结果表明,随着黏粒含量的增加,黄土试样微观结构由分散结构变为致密结构,部分颗粒的接触方式由支架接触变为镶嵌接触,颗粒连接由葱皮连接或桥接变为嵌埋连接,相应地孔隙则由支架大孔变为黏粒间微小孔隙,从而一定程度上降低了黄土的渗透性。[结论]黄土渗透系数受黏粒含量、含水率的影响规律相似,可通过微观结构对其影响机理进行解释。

[Objective]An experiment focused on the effect of different clay content on the permeability coefficient of loess was carried out,to reveal the influence of clay content on the permeability coefficient and its microscopic mechanism,and then to provide a scientific basis for the permeability of theory and engineering practice of loess.[Methods]Self-made wet sieve device under negative pressure was applied to screen loess samples with different clay content.Laser particle analyzer was carried out to track measurement clay content of the loess soil.Different clay content of the loess samples were made to the natural dry density,but with different moisture content using static pressure method,and then saturated by infiltration experiment.[Results]The clay content of the loess had a great influence on its permeability.For samples with the same moisture content,the permeability of loess reduced gradually as the clay content increased.In addition,permeability coefficient exhibited an exponential and negative relationship with the content of clay as independent variable.The permeability coefficient decreased with the increase of the initial water content forthose samples with same clay content.With the increase of clay content,the microstructure of loess samples changed from a dispersed structure to a dense structure.The contact of some particles changed from bracket contact to mosaic contact.The particle connections were connected or bridged into embedded connections.The pores changed from stent macroporous to small ones among clay particles,whereby the permeability of the loess was reduced to some extent.[Conclusion]The responses of the permeability coefficient of loess to clay content and moisture content were similar.Its impact mechanism can be explained by the microstructure.