原状马兰黄土抗剪强度的各向异性

发布时间：2018-06-04 17:01

本文选题：马兰黄土 + 直剪试验　；参考：《太原理工大学》2017年硕士论文

【摘要】：黄土是一种特殊的结构性土,受生成环境以及应力历史环境的影响,存在明显的孔隙型结构和竖向节理。黄土沉积过程中形成的水平成层性特征以及孔隙和竖向节理的存在,使黄土的力学性质存在明显的差异。不同区域内的黄土,不同影响因素对其力学性质的影响也不尽相同。地球上黄土和黄土状土的面积约为1300万km2,占到全球大陆总面积的9%以上,分布十分广泛。尤其是在中国的中西部以及北部地区有广泛的黄土覆盖区。随着国家“西部大开发”战略以及“一带一路”战略的实施,黄土地区工程数量日趋增加且规模逐步扩大。同时在公路、铁路、桥梁、隧道等多种交通基础设施的建设中,也都面临着各种黄土问题。因此,对于黄土力学特性的研究变得日臻重要。本文基于前人关于黄土抗剪强度以及各向异性方面的研究,通过人工开挖探井,取原状马兰黄土试样,密封后用被子包好,运回实验室。通过干密度、孔隙比、颗粒重度、液塑限、粒径分析等物理实验和室内直剪试验,寻找其间差距并究其原因。直剪试验所用试样,为烘干的含水率为0的原状马兰黄土,用线切割机将烘干的黄土切割成圆柱状,然后用细砂纸打磨成标准样。分别对取自7个探井的试样,从竖直向(剪切面平行于水平向)、东西向(剪切面平行于坡向)和南北向(剪切面平行于走向)三个方向做直剪试验,每个方向剪3个试样,共63组直剪试样,分别测其抗剪强度和剪切过程中的竖向位移量。结果表明:该区域内的马兰黄土,存在明显的各向异性;该区域内的原状马兰黄土在含水率为0时,从不同方向剪切试样,试样在剪切过程中的竖向位移量无明显规律;该区域内的原状马兰黄土,竖直向的密实度和抗剪强度明显大于水平向,竖直向的抗剪强度约为水平向的1.15倍;东西和南北向的抗剪强度差异不大,较为接近,南北向略大于东西向。可初步认为:该区域内的马兰黄土,竖向节理和孔隙性结构特征,对其力学性质的影响更为明显。
[Abstract]:Loess is a special structural soil, which is influenced by the generated environment and the historical environment of stress. There are obvious pore structure and vertical joint. The horizontal stratification characteristics and the existence of pore and vertical joints in the process of loess deposition make the mechanical properties of the Loess distinct difference. The Loess in different regions is different. The influence factors have different effects on the mechanical properties of the earth. The earth's loess and loessial soil area is about 13 million km2, accounting for more than 9% of the total area of the global continent and widely distributed, especially in the central and western regions of China and in the northern region. With the implementation of the "road" strategy, the number of projects in the loess region is increasing and the scale is gradually expanding. At the same time, all kinds of loess problems are faced in the construction of road, railway, bridge, tunnel and other transportation infrastructure. Therefore, it is becoming more and more important to study the mechanical properties of loess. And the study of anisotropy, through the artificial excavation of the well, take the original Ma Lan loess sample, sealed with the quilt wrapped, transported back to the laboratory. Through the dry density, the pore ratio, the grain weight, the liquid plastic limit, the particle size analysis and other physical experiments and the indoor direct shear test, looking for the gap between them and the reasons. The original Ma Lan loess, which has a water rate of 0, cuts the dried loess into a cylindrical shape with a wire cutting machine and then grinded into a standard sample with fine sand paper. The specimens from 7 exploratory wells, respectively, are vertical shear tests from the vertical direction (the shear plane parallel to the horizontal direction), the east-west direction (the shear plane parallel to the slope) and the south north direction (parallel to the direction of the shear plane), respectively. The shear strength and the vertical displacement in the shear process were measured in 63 groups of 3 samples in each direction. The results showed that the Ma Lan loess in the region had obvious anisotropy, and the vertical displacement of the original Ma Lan loess in the region was in the shear process when the water content was 0. The original Ma Lan loess in this area has a vertical direction of compactness and shear strength that is obviously greater than the horizontal direction, and the vertical shear strength is about 1.15 times that of the horizontal direction; the shear strength of the East and the west is little different, and the north and south direction is slightly larger than the east west direction. It can be preliminarily considered that the Ma Lan loess in this area is vertical. The mechanical properties of joints and porous structures are more obvious.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU444

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