全风化花岗岩剪切特性试验研究

发布时间：2018-05-19 05:33

本文选题：全风化花岗岩 + 三轴试验　；参考：《华南理工大学》2015年硕士论文

【摘要】：花岗岩在我国东南部的分布范围非常广泛,由其风化而来的全风化花岗岩,有着特殊的性质,且在工程上经常遇到,需要对全风化花岗岩各项物理力学性质有着充分的认识,才能避免工程事故的发生。本文针对深圳某基坑的全风化花岗岩进行了剪切特性方面的研究,对其原状土和重塑土进行不同围压下的固结排水和固结不排水试验,讨论其应力-应变关系、剪切破坏特征,基于“结构贡献率”分析受荷过程中结构性的变化规律,并结合本课题组对花岗岩残积土的研究成果,对比分析全风化花岗岩和花岗岩残积土物理力学性质的差异。主要的研究成果如下:1.本文研究的全风化岩孔隙比较大,天然含水率不高,粗颗粒含量较高,属于含砂的中液限粘质土(水电部SD128-84分类法)或粉粘土质砂土(吴能森综合分类法)。2.从固结排水和固结不排水三轴试验得到:(1)原状全风化花岗岩具有较强的结构性,但随着围压的增大,在固结压缩阶段结构性的作用逐渐被削弱。(2)结构性的存在使原状土的粘聚力高于重塑土,对内摩擦角影响不大。(3)原状样没有出现单一明显的剪切带,而是呈现出复杂的破坏形态,土样表面凹凸不平;而重塑土样均呈现出较明显的光顺鼓状破坏。3.基于“结构贡献率”得到原状土在固结作用和剪切过程中结构性的变化规律:(1)原状土的结构性将随固结压力增大而降低直至完全消失。(2)原状结构性在剪切过程中经历了从逐渐发挥到逐渐损伤的过程。以峰值结构贡献率来衡量土体的结构性大小。(3)以“结构贡献率”曲线下降起始点作为应变局部化开始产生的标志,围压越大,应变局部化越早发生。(4)不排水条件下土体结构的剪切破坏速率相对于排水条件下有一定的减缓,同时有效应力的减小也削弱了其结构性的发挥。4.对比全风化花岗岩和花岗岩残积土得到:(1)全风化岩的平均含水量、孔隙比及其细粒部分的液限和塑性指数都比残积土小,粗颗粒含量明显多于残积土。(2)基于“结构贡献率”的对比,可知全风化岩的结构性强于残积土。(3)同一围压下,原状全风化岩比残积土表现出更高的强度和剪切模量。对于重塑土,全风化岩排水强度高于残积土,但在不排水强度低于重塑残积土。(4)土体中粗细颗粒的含量、孔隙比、围压和排水条件对土体的破坏形态有较大影响。(5)掺砂对本身细颗粒含量较多的花岗岩残积土的破坏形态影响较大,而对于本身粗颗粒含量较多的全风化花岗岩,则影响较小。
[Abstract]:The granite is widely distributed in the southeast of China. The fully weathered granite from the weathered granite has special properties and is often encountered in engineering, so it is necessary to have a full understanding of the physical and mechanical properties of the weathered granite. In order to avoid the occurrence of engineering accidents. In this paper, the shear characteristics of fully weathered granite in a foundation pit in Shenzhen are studied. The consolidation and undrained tests of undisturbed soil and remolded soil under different confining pressures are carried out, and the stress-strain relationship and shear failure characteristics are discussed. Based on the "structural contribution rate" analysis of the structural changes in the process of loading, and combined with the research results of our group on granite residual soil, the physical and mechanical properties of fully weathered granite and granite residual soil are compared and analyzed. The main research results are as follows: 1: 1. The total weathered rock studied in this paper has relatively large porosity, low natural moisture content and high coarse particle content. It belongs to medium liquid limit clay soil containing sand (SD128-84 classification of Ministry of Water and electricity) or silty clay sandy soil (Wu Nenson comprehensive classification method). From the triaxial tests of consolidated drainage and consolidation undrained, it is found that the intact fully weathered granite has a strong structure, but with the increase of confining pressure, During the consolidation and compression stage, the effect of structural structure was gradually weakened. 2) the cohesive force of undisturbed soil was higher than that of remolded soil, but had little effect on the internal friction angle. The surface of the soil samples is uneven, while the reconstructed soil samples show obvious smooth and drum damage. 3. Based on the "contribution rate of structure", the structural changes of undisturbed soil during consolidation and shear process are obtained. (1) the structure of undisturbed soil decreases with the increase of consolidation pressure, and then disappears completely. 2) during shear process, the structure of undisturbed soil decreases. Has experienced the process from gradually exertion to gradually injures. The structural size of soil is measured by the peak structural contribution rate. (3) the decreasing starting point of the "structural contribution rate" curve is taken as the symbol of the beginning of strain localization, and the larger the confining pressure, the greater the confining pressure is. The earlier strain localization occurs. (4) the shear failure rate of soil structure under undrained condition is slower than that under drainage condition, and the decrease of effective stress also weakens its structural exertion. Comparing fully weathered granite and granite residual soil, the average water content, porosity ratio and the liquid limit and plastic index of the fine grain part of the weathered rock are smaller than those of the residual soil. Based on the comparison of "structural contribution rate", it can be concluded that the structure of total weathered rock is stronger than that of residual soil. 3) under the same confining pressure, the strength and shear modulus of undisturbed weathered rock are higher than that of residual soil. For remolded soil, the drainage strength of total weathered rock is higher than that of residual soil, but the undrained strength is lower than that of remolded residual soil. Confining pressure and drainage condition have great influence on the failure form of soil mass. (5) Sand admixture has a great influence on the failure form of granite residual soil with more fine grain content, while it has less effect on the total weathered granite with more coarse grain content.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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