黄土垂直节理形成机理的试验模拟

李同录+王红+付昱凯+梁燕

基金项目：国家自然科学基金项目(41372329)；国家重点基础研究发展计划(“九七三”计划)项目(2014CB744701)

摘要：通过室内试验模拟自然沉积作用下黄土中水的渗透性，发现黄土垂直节理是地表水入渗过程中形成的。根据室内模型试验，建立一理想颗粒排列模型，利用TEN15型张力计实测的土水特征曲线，计算从饱和到非饱和状态的变化过程中土颗粒的相互作用力的变化。结果表明：地表水在下渗过程中，初始沉积的黄土含水量发生变化，基质吸力和表面张力产生的粒间引力也发生变化；粒间引力会随着粒间距的减小而急剧增大，而且其随含水量的变化规律与粒间距的大小有很大关系；由于初始沉积的黄土粉粒结构疏松，粒间有极弱的支撑，改变含水量状态产生的粒间引力在较小的量级便会使土颗粒相互靠近，而颗粒间距减小，则粒间引力急剧增大，土体整体收缩导致局部拉裂形成垂向裂隙，即垂直节理。

关键词：黄土；垂直节理；形成机理；模型试验；渗透；表面张力；基质吸力；粒间引力

中图分类号：P642.13+1文献标志码：A

Test Simulation on the Forming Mechanism of Loess Vertical Joints

LI Tonglu1, WANG Hong1, FU Yukai1, LIANG Yan2,3

(1. School of Geology Engineering and Geomatics, Changan University, Xian 710054, Shaanxi, China;

2.School of Highway, Changan University, Xian 710064, Shaanxi, China; 3. Key Laboratory for Special

Area Highway Engineering of Ministry of Education, Changan University, Xian 710064, Shaanxi, China)

Abstract: It is observed that the loess vertical joints form in the process of rainfall penetration by the model test for simulating loess penetration under the sedimentation. According to the model test, an ideal model of soil particle arrangement was built; based on the soilwater characteristic curve of loess sample measured by TEN15 tension meter, the interaction force between soil particles under different moisture contents was induced by the relationship between matric suction and curvature radius of water shrink film. The results show that the vertical joint is caused by the change of interparticle force because of the matric suction and surface tension in the process of rainfall penetration; the interparticle force increases sharply with the decrease of the interparticle distance, and the relationship between the interparticle force and water content is significantly influenced by the interparticle distance; the structure of initial sediment loess is loose and the support of interparticle is weak, so that the particles will be close to each other because of the interparticle force at small order caused by the change of water content, and the interparticle force increases sharply with the decrease of the interparticle distance, and then the shrinkage of soil leads to local cracks and forms vertical joints.

Key words: loess; vertical joint; forming mechanism; model test; penetration; surface tension; matric suction; interparticle force

0引言

垂直节理是黄土中普遍发育的一种独特构造，是非构造成因的一种破裂。垂直节理一般是地表水或地下水的运移通道，地表水灌入地下后，常沿节理发生潜蚀，使其导水性增强，加剧黄土的侵蚀，常对各类工程造成危害，因此，学者们对黄土区的渗透性进行了大量研究［19］。

黄土中垂直节理的存在是被广泛公认的现象，关于其形成机理的研究较少，认识尚不统一［10］。……