红黏土竖向压缩性能对侧限条件的响应机理试验研究

发布时间：2018-05-11 23:40

本文选题：红黏土 + 侧限条件　；参考：《东华理工大学》2017年硕士论文

【摘要】：土是非连续、非均匀、各向异性体,它是在各种复杂地质环境中经过漫长的地质作用而孕育形成的,外界环境的变迁会使其物理力学性质发生质的变化。对于工程建设而言,土的承载力是最普遍、最重要的力学参数,实验室内通常借助压缩试验来研究土体强度及变形特性。在自然界中,埋藏在地表深部的岩土体通常处于全围压受力状态,从侧限角度上讲即处于全侧限受压状态。除此之外,自然界中以及工程建设中还分布着处于各种不同的侧限受压条件下的岩土体,参照临空面的数量和相对位置关系可将侧限受压工况划分为:(1)无侧限受压工况;(2)单面侧限受压工况;(3)邻面侧限受压工况;(4)对面侧限受压工况;(5)三面侧限受压工况;(6)完全(四面)侧限6种受压工况。然而,现有的试验条件只能模拟无侧限受压和完全侧限受压工况下岩土体强度、变形特征,而无法适用于其他侧限工况下岩土体的试验测试需求。基于此,本文以国家自然科学基金项目“极端降雨作用下红壤土坡响应试验与灾变机理研究”(项目编号:41462011)为依托,以江西省南昌市典型的第四系红黏土为研究对象,通过自主研发一种侧限可调节式岩土体竖向压缩辅助试验装置,将其与液压伺服压力机相结合,分别开展不同基本物理力学性质、不同侧限条件下红黏土的竖向压缩试验。着重研究了重塑红黏土试样对部分侧限条件的力学响应特征,并借助先进的数值模拟试验手段构建计算模型,以期从竖向应力与应变、及剪切应变率的发展演化等角度全面分析不同侧限工况下岩土体受压过程中所表现出的差异性。通过室内侧限竖向压缩试验和FLAC3D数值模拟试验相结合,经对比分析,较为准确地分析了红黏土在各种复杂工况下的变形及强度特征。该研究将为进一步丰富岩土工程地下空间的利用开发理论提供有益的借鉴。本文的主要工作与研究成果如下:(1)在江西省南昌市经济开发区某段公路施工处采集到大量红黏土试样,对红黏土进行室内基本物理力学性质试验,从而获取红黏土的颗粒级配、塑限WP、液限WL、黏聚力c、内摩擦角φ等基本物理力学参数。(2)通过对不同初始含水率、不同最终含水率和不同干密度的红黏土开展六种侧限工况下的竖向压缩试验,并对各类侧限条件下的红黏土应力-应变关系发展演化特征进行了阶段性划分,剖析了其变化机理。(3)随着最终含水率的增加,无侧限、单面、对面和四面侧限红黏土峰值强度均呈现出先升高后降低的规律。当最终含水率一定时,红黏土残余强度在各侧限条件的大小关系为:无侧限单面侧限对面侧限邻面侧限三面侧限。红黏土的峰值强度、残余强度、峰值应变和压缩模量总体上均随干密度的增大而增大。(4)对室内红黏土侧限竖向压缩试验进行FLAC3D数值模拟试验,针对红黏土立方体试样及试验条件的实际受压工况,采用正六面体模型,实现模拟立方体在无、单面、邻面、对面、三面以及四面侧限状态下的响应机理试验研究,通过对数值模拟和室内试验的试验结果进行对比分析,发现数值模拟和室内试验的结果一致性较好,证明了数值模拟方法的可靠性和有效性,也较好例证了当室内外试验条件难以达到时借助FLAC3D数值模拟手段来完成试验分析的可行性。
[Abstract]:Soil is a non continuous, nonuniform, anisotropic body, which is conceived by a long geological process in various complex geological environments. The changes in the external environment will make the physical and mechanical properties change qualitatively. For engineering construction, the soil bearing capacity is the most common and most important mechanical parameter, usually in the laboratory with the aid of compression. The soil strength and deformation characteristics are studied in the experiment. In nature, the rock and soil buried in the deep surface of the earth are usually in the state of full confining pressure. From the lateral point of view, the rock and soil are in the state of the full lateral pressure. In addition, in nature and in the construction, the rock and soil under the different lateral confinement conditions are also distributed in the engineering construction. The relationship between the number and relative position of the plane can be divided into: (1) unconfined compression conditions; (2) unilateral side limited compression conditions; (3) side limited compression working conditions of adjacent surface; (4) face side limited pressure condition; (5) three side side limit compression conditions; (6) completely (four sides) side limit 6 compression conditions. However, the existing test conditions can only simulate the unconfined limit. The strength and deformation characteristics of rock and soil soil under compression and full lateral confinement can not be applied to the test and test requirements of rock and soil under other conditions. Based on this, this paper is based on the National Natural Science Foundation Project "response test and catastrophe mechanism study of red soil slope under extreme rainfall" (project number: 41462011), and Jiangxi The typical Quaternary red clay in Nanchang province is the research object. By independently developing a side limited adjustable rock soil vertical compression auxiliary test device, it is combined with the hydraulic servo press to carry out the vertical compression test of red clay under different basic physical and mechanical properties and different side limits. The emphasis is on the study of remolding red viscosity. The mechanical response characteristics of the soil specimen to some side limit conditions and the advanced numerical simulation test method are used to construct the calculation model in order to analyze the difference in the rock and soil compression process under the different side limit conditions from the angle of vertical stress and strain and the development and evolution of shear strain rate. The deformation and strength characteristics of red clay under various complex conditions are analyzed accurately by the combination of test and FLAC3D numerical simulation test. This study will provide useful reference for further enriching the theory of underground space utilization and development of geotechnical engineering. The main work and research results of this paper are as follows: (1) in the south of Jiangxi Province A large number of red clay samples were collected at a section of highway construction in Changshi Economic Development Zone, and the basic physical and mechanical properties of red clay were tested, and the basic physical and mechanical parameters, such as particle size distribution of red clay, plastic limit WP, liquid limit WL, cohesive C, internal friction angle, etc. were obtained. (2) different water cut rates and no final water content were obtained by different initial water content. The vertical compression test of the red clay with the same dry density was carried out under six side limit conditions, and the evolution characteristics of the stress strain relationship of red clay under different side conditions were divided and the change mechanism was analyzed. (3) with the increase of the final water content, the peak strength of the unconfined, single side, opposite and four sides of the red clay was all present. When the final water content is certain, the relationship between the residual strength of the red clay at all side limits is that the side limit of the unconfined single side side limits the side limit of the side limit of the opposite side of the three side side limits. The peak strength, the residual strength, the peak strain and the compressive modulus of the red clay increase with the increase of the dry density. (4) to the room The vertical compression test of red clay side limit is carried out by FLAC3D numerical simulation test. In view of the actual compression conditions of red clay cubes and test conditions, the positive hexahedron model is adopted to study the response mechanism of the simulated cube under the condition of no, single, adjacent, opposite, three and four sides, through the numerical simulation and the indoor test. The experimental results are compared and analyzed. It is found that the results of the numerical simulation and the laboratory test are in good agreement, which proves the reliability and effectiveness of the numerical simulation method. It also exemplifies the feasibility of completing the test analysis with the help of FLAC3D numerical simulation when the test conditions are difficult to reach in the room.

【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU446

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