石灰改良泾阳黄土平面应变试验研究

发布时间：2018-06-11 18:22

本文选题：石灰改良黄土 + 平面应变　；参考：《西北农林科技大学》2015年硕士论文

【摘要】：黄土作为一种特殊土体,广泛分布在我国中西部地区。随着经济的快速发展,不可避免的在黄土地区进行工程建设,因黄土具有高压缩性、湿陷性和遇水敏感性等天然缺陷,黄土填料很难满足现代工程对地基的强度、变形和耐久性等高标准要求。合理对黄土进行改良使其技术和经济上满足工程要求是很有必要的,为类似的工程设计提供有效的参数,对我国经济发展有重要的现实意义。本文在前人研究改良黄土的力学特性及测试手段的基础上,利用PY-10型平面应变仪来研究石灰改良黄土在不同影响因素下的变形、强度及局部化变形特性,即不同石灰掺入量、不同含水率、不同养护龄期、不同固结围压和不同固结应力比。整理、分析土体在不同影响因素其变形和强度的变化规律,进而得出影响石灰改良剪切强度原因,最后尝试探讨影响土体局部化变形的原因,主要的研究结论如下:(1)石灰改良泾阳黄土的击实特性泾阳黄土在不同石灰掺入量下击实试验均表现为干密度随着含水率增加先增大后显著减小;随着黄土中石灰掺入量的增加,石灰土的最优含水率增大,最大干密度减小,且掺入石灰后的黄土,击实曲线较素土为平缓;在实际工程中石灰与黄土拌和后应及时压实,否则会引起最大干密度的下降而影响压实效果。(2)石灰改良泾阳黄土的应力-应变关系石灰改良黄土在平面应变下应力-应变曲线随影响因素的不同有硬化型和软化型两种,在养护龄期较长时基本呈软化曲线,土体表现为脆性破坏;而在养护龄期较短时基本呈硬化曲线,土体表现为延性破坏。应力-应变曲线受围压、石灰掺入量、含水率、养护龄期、固结应力比影响明显,随着初始含水率减小、固结围压增大和石灰掺入量的增大其应力-应变曲线有不同程度的增高;养护龄期、固结应力比的不同,土体应力-应变曲线表现为不同的形态。(3)石灰改良泾阳黄土的抗剪强度在平面应变下固结应力比、石灰掺入量和含水率对土体抗剪强度有明显的影响;无论是等压固结或不等压固结,随着土体含水率的增大凝聚力呈明显降低,内摩擦角随着含水率的增大降低幅度较小。土体的凝聚力随掺灰量增加先增大后减小;等压固结下,土体的内摩擦角随掺灰量增大基本呈增大趋势;而在不等压固结下,当土体的初始含水率较小时内摩擦角随掺灰量增大而减小,当土体的初始含水率较大时内摩擦角随掺灰量增大而增大。(4)石灰改良泾阳黄土主应力之间的关系中主应力随着剪切的时间的变化大致分为三个阶段。剪切初期中主应力随轴向应变迅速增加,曲线初始斜率较大;剪切后期中主应力缓慢增长,曲线斜率也逐渐减小。在土体剪切过程中,剪切初期σ1、σ2随轴向应变的增大而增加;随着剪切的进一步增大,应力-应变曲线σ1~ε1和σ2~ε1出现较为明显的拐点,两条曲线的拐点基本同时出现,且拐点大概在轴向应变ε1=3%。(5)石灰改良泾阳黄土的剪切带特性平面应变下土体的剪切带性状主要有三种类型:“X”型剪切带形状、“V”型剪切带形状和单一型剪切带形状;采用Mohr-Columb理论计算土体剪切带的倾角值为64°~68°范围之内,而实际测量剪切的带倾角值为62°~70°范围之内,实测倾角值十分接近于理论计算倾角值。
[Abstract]:As a special soil, loess is widely distributed in the central and western regions of China. With the rapid development of the economy, it is inevitable to carry out engineering construction in the loess region. Because of the natural defects such as high pressure shrinkage, collapsibility and water sensitivity, the Loess filler is difficult to meet the high standard of the foundation, such as the strength, deformation and durability of the foundation. It is necessary to make rational improvement of the Loess so that it is necessary to meet the engineering requirements technically and economically. It is of great practical significance for the economic development of our country to provide effective parameters for similar engineering design. On the basis of previous studies on the mechanical properties of loess and the test hand section, the PY-10 plane strain gauge is used in this paper. The deformation, strength and local deformation characteristics of lime modified loess are studied under different influence factors, that is, different lime content, different water content, different curing age, different consolidation confining pressure and different consolidation stress ratio. The change law of deformation and strength of soil in different influence factors is analyzed, and then the influence of lime modified shear is obtained. The causes of shear strength are discussed at last. The main research results are as follows: (1) the main results are as follows: (1) the compaction characteristic of Jingyang loess with lime improvement, the dry density of Jingyang loess under different lime content shows that dry density increases significantly with the increase of water content; with the increase of lime content in the loess, The optimum water cut rate of lime soil increases and the maximum dry density decreases, and the compaction curve of loess after adding lime is more gentle than that of plain soil. In actual engineering, lime and loess should be compacted in time, otherwise the maximum dry density will be caused by the decrease of maximum dry density. (2) the stress strain of the lime modified Jingyang loess is related to the lime improvement yellow. The stress-strain curves of soil under plane strain are two kinds of hardened and softening types with different influence factors. When the curing age is long, the softening curve is basically presented, and the soil is brittle failure, while the soil is basically hardening curve when the curing age is short, and the soil is ductile. The stress strain curve is subjected to confining pressure, lime content and water content. Rate, curing age, consolidation stress ratio is obviously affected. With the decrease of initial water content, the stress strain curve of the consolidation confining pressure and the amount of lime content increase in different degrees; the curing age, the consolidation stress ratio is different, the soil stress strain curve is different form. (3) the shear strength of the lime improved Jingyang loess is in the shear strength. The consolidation stress ratio under plane strain, lime content and water content have an obvious influence on the shear strength of soil. No matter isobaric consolidation or unequal pressure consolidation, the cohesive force decreases with the increase of soil moisture content, and the internal friction angle decreases with the increase of water content. The cohesiveness of soil mass increases first and then decreases with the increase of the amount of cement. Under the constant pressure consolidation, the internal friction angle of the soil increases basically with the increase of the amount of cement. While under the unequal pressure, the friction angle of the soil decreases with the increase of the amount of cement. When the initial water content is larger, the internal friction angle increases with the increase of the amount of cement. (4) lime improved the main stress of Jingyang loess The main stress in the inter relationship is roughly divided into three stages with the change of the shear time. In the early shear, the main stress increases rapidly with the axial strain, the initial slope of the curve is larger, and the main stress increases slowly in the late shear, and the slope of the curve decreases gradually. During the shear process, the initial shear stress is increased with the increase of the axial strain. With the further increase of shearing, the stress strain curve Sigma 1~ epsilon 1 and sigma 2~ epsilon 1 appear more obvious inflection point, and the turning point of the two curves appears at the same time, and the turning point is about three types of shear zone of soil under the characteristic plane strain of the shear zone of the modified Jingyang loess with the axial strain of 1=3%. (5) lime: "X" shear zone Shape, the shape of "V" shear band and the shape of a single shear band, and the angle value of the shear zone of soil is within the range of 64 degrees ~68 degrees with the Mohr-Columb theory, while the actual measured shear zone angle is within the range of 62 ~70 degrees, and the measured dip value is very close to the theoretical calculation angle value.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411

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