【作者】 李守存；

【导师】 党进谦；

【作者基本信息】 西北农林科技大学 ， 岩土工程， 2005， 硕士

【摘要】 黄土是我国北部广泛分布的一种特殊土,是一种常见的工程用土,广泛应用于公路、高土石坝等工程的建设。近几年来,随着公路﹑机场﹑高土石坝修建的蓬勃兴起,使得对非饱和黄土的抗拉性状的研究更具有现实意义。本文以非饱和黄土为研究对象,以直剪、基质吸力和单轴拉伸试验为手段,对非饱和黄土的抗拉强度、拉伸变形以及试样含水率、干密度对抗拉强度和拉伸变形的影响进行了系统的试验研究和深入的理论分析,并在此基础之上分析讨论了黄土抗拉强度与基质吸力、凝聚力c 的关系并提出了建议性的公式。取得的主要试验研究成果如下: 1. 试样含水率、干密度是影响非饱和黄土抗拉强度的主要因素。试样含水率对抗拉强度的影响:随着含水率的增大,原状黄土抗拉强度减小,重塑黄土抗拉强度先增大而后减小,相同情况下,原状黄土抗拉强度要高于重塑黄土抗拉强度。试样干密度对重塑黄土抗拉强度的影响:含水率相同抗拉强度随干密度的增大而增大。2. 试样含水率、干密度对非饱和黄土拉伸变形有重要影响。试样含水率对拉伸变形的影响:在试验含水率范围内试样拉伸变形均是先减小后增大,低含水区原状黄土的拉伸变形比重塑黄土的大,高含水区重塑黄土的比原状黄土的大。试样干密度对重塑黄土拉伸变形的影响:试样含水率相同干密度越大,试样拉伸变形越大。3. 在黄土拉伸变形分析中提出临界孔隙比概念,其大小与土的类别、含水率和试验条件有关。在施加荷载过程中孔隙比增大,到临界孔隙比试样破坏。4. 非饱和黄土抗拉强度与凝聚力的关系。从试验数据的分析结果看,原状、重塑黄土的抗拉强度值均小于对应的凝聚力c 值,呈线性关系,并给出了相关关系式。5. 非饱和黄土抗拉强度与土体内部基质吸力的关系。从试验数据的分析结果看,原状、重塑黄土的抗拉强度均小于土体内的基质吸力,二者呈线性关系,但是随着基质吸力的增大,直线段出现偏折,文中给出了试验范围内各阶段的关系表达式。6. 非饱和黄土的抗拉结构强度主要来源于胶体结构的联结强度,其值可由原状黄土抗拉强度值减去重塑黄土抗拉强度值。非饱和黄土的抗拉结构强度与试样含水率呈幂函数关系,是原状黄土抗拉强度的主要组成部分,与凝聚力c 呈线性关系。更多还原

【Abstract】 Loess is a kind of special soils, which is widely spread in Northern China. In the construction of some projects, such as roads and high earth dams, loess is often used as the building material. Recent years, building constructions, such as roads, airdromes and high earth dams are rising, which made that the study on tensile characteristics of loess is very significant. Focused on the unsaturated loess, the characteristics of the unsaturated loess such as tensile strength, tensile deformation and effect of sample water content, dry density were scheduled systematic experimental study and deep theory analysis in this paper by means of direct shear, suction and monaxial tension tests. According to the above test results, connections between tensile strength and suction are analyzed, connections between tensile strength and direct shear cohesion are discussed, and formulas expressed these connections are given. Main test research results can be gained as follows: 1.Sample water content and dry density are main affecting factors on tensile strength of loess. With the increasing of water content,tensile strength of undisturbered loess decrease, that of remolded loess increase firstly, and then decrease. In the same condition, tensile strength of undisturbered loess is higher than that of remolded loess. Tensile strength of remolded loess increases with dry density increasing under same water condition. 2.Sample water content and dry density are main affecting factors on tensile deformation of loess. Within test water content, sample tensile deformation decrease first, and second increase. In lower water content section, tensile deformation of undisturbered loess is more than that of remolded loess; In higher water content section, tensile deformation of undisturbered loess is less than that of remolded loess. Tensile deformation of remolded loess increases with dry density increasing under same water condition. 3. The concept of critical void ratio is put forward in analysis on tensile deformation, the value of which is affected by soil kinds, water content and experimentation conditions. Void ratio is increasing during adding loads until critical void ratio or sample destroyed. 4.Connection between tensile strength and direct shear cohesion is linear; Tensile strength is lower than direct shear cohesion. 5.connections between tensile strength and suction is also linear, Suction is much higher than tensile strength. 6.Tensile structural strength bring from connection of cementing material, which can be gotten by tensile strength of undisturbered loess subtracting that of remolded loess. Connections between tensile structural strength and tensile strength of undisturbered loess, direct shear cohesion are discussed, and formulas be given in the paper.更多还原