泾阳南塬黄土斜坡结构面发育特征及其影响效应

DEVELOPMENTAL CHARACTERISTICS AND EFFECTS OF STRUCTURAL SURFACES OF LOESS SLOPES IN SOUTHERN JING-YANG LOESS PLATEAU

黄土斜坡中常发育有大量的结构面,这些结构面不仅破坏土体的连续性,同时对斜坡的渗流场、变形场甚至稳定性产生显著的影响。本文以泾阳南塬为研究区,通过现场调查和室内试验及数值模拟等方法,对结构面的发育特征和影响效应进行了系统研究。取得主要结果包括:(1)考虑结构面的形成原因及其对坡体的影响效应等,从宏观、细观及微观3个尺度提出了黄土结构面的分级分类方法,将黄土结构面分为5级,两个大类和25个小类。(2)根据现场实测结果,研究区结构面多分布在距坡肩较近位置,且其走向与坡面走向基本一致,结构面的延伸长度、张开度及错动高差等随其距坡肩距离的增加而增大。(3)由数值模拟结果可见,距坡肩不同距离和不同深度的结构面扩展特性及其对坡体变形破坏的影响差异较大。距坡肩较近和较深的结构面在重力作用下更容易扩展。随着结构面与坡面距离的增加,坡体稳定系数先减小后增大并逐渐趋于一个稳定值。随着结构面深度的增加,坡体稳定系数逐渐减小,最终趋于一个稳定值。研究结果可为黄土边坡的稳定性评价提供一定的地质依据。

Structural surfaces are generally developed widely in the loess slope, can not only alter the continuity of the soil, but also present a significant influence on the seepage, deformation, and stress fields, as well as the stability of the loess slope. In this study, the developmental characteristics and effects of structure surface of loess slope in southern Jing-Yang loess plateau were researched systematically through field investigations, experiments, and numerical simulations. The main results are presented as follows:(1)Considering the difference of formation and influence, the structural surface of the loess slope is classified from the perspective of macro, micro and micro multi-scales into 5 classes and 2 groups and 25 categories.(2)According to the results of the field investigation, the structural surfaces are mostly distributed near the slope shoulder, the orientation of the structural surface is generally in accordance with that of the loess slope. And the length, width, and displacement of the structural surface generally increase with the increase of distance from the slope shoulder.(3)The numerical simulation results show that the development characteristics and influence of the structural surface are various with the change of depth and location. The surface that is near the shoulder and shows large depth is easy to develop. The FOS of the loess slope decreases first and then increases to reach a stable value, with the increase of the distance of the surface from the shoulder. In addition, the FOS gradually decreases to reach a certain value with the increase of surface depth. The results of the paper can provide some basis for the stability evaluation of loess slopes.