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贵广高铁尖山营特大桥桥区全风化膨胀岩膨胀特性试验研究

发布时间:2018-04-10 05:22

  本文选题:全风化膨胀岩 切入点:SEM 出处:《西南交通大学》2017年硕士论文


【摘要】:尖山营特大桥位于南北向川黔经向构造体系内的一条紧密状向斜构造——昌明向斜——近核部地区,随当地早、雨季的气候变化而异常升降。本文以此为研究背景,研究尖山营地区地表裸露的全风化灰白色泥页岩在荷载作用下的膨胀特性。本文选取初始含水率、干密度、初始加压荷载值三个主要因素,分析研究区岩土体膨胀率、膨胀力在以上三个因素作用下的变化规律,建立膨胀力与初始含水率、干密度、初始加压荷载间的关系。本文主要研究成果入下:通过微观组构分析,得到全风化膨胀岩的镜下主要呈片状结构,矿物成分主要为伊利石,含量为90.4%,其次是石英,含量为9.6%。通过室内基本土工试验,得到全风化扰动膨胀岩的无荷载膨胀率试验,当试样的干密度较大时,土体的膨胀变形可明显划分为:初始缓慢膨胀、加速膨胀、后期稳定膨胀阶段三个阶段;当干密度较小时,初始缓慢膨胀阶段与加速膨胀阶段会合二为一。同时,干密度越大,试样达到膨胀稳定阶段需要的时间越长。无论在任何含水率状态下,试样的变形量随干密度的增大而显著增大。初始含水率对无荷载状态的一维膨胀速率的影响较干密度大。干密度对无荷载膨胀率大小的影响较含水率大。土体平衡膨胀力与干密度之间满足指数关系,膨胀应变与竖向应力呈logistic函数关系。经过7个判别指标的评判结果,得出尖山营特大桥地表出露的全风化膨胀岩属于强膨胀岩。同时,自由膨胀率是对膨胀岩的分类与判别最为准确与高效的一个指标。结合针对全风化膨胀岩的室内宏、微观试验结果,经过理论分析得出:全风化膨胀岩的胀缩机理以扩散双电层理论为主,晶格扩张理论为辅;原状膨胀岩的膨胀机理考虑主要以晶格扩张为主。
[Abstract]:The Jianshanying Bridge is located in a tight syncline-Changming syncline-near-core area in the south- north Sichuan-Guizhou meridional structural system, which rises and falls abnormally with the local climate change in the early and rainy seasons.In this paper, the expansion characteristics of fully weathered gray-white shale exposed on the surface of Jianshanying area under load are studied.In this paper, three main factors of initial moisture content, dry density and initial compressive load are selected to analyze the variation law of expansion rate and expansion force of rock and soil in the study area, and to establish the expansion force, initial moisture content and dry density.The relationship between initial compressive loads.The main results of this paper are as follows: through microscopic fabric analysis, it is found that the weathered expansive rock is mainly flake structure under microscope, the mineral composition is mainly Illite, the content is 90.4 and the next is quartz, the content is 9.6.Through the basic geotechnical test in laboratory, the load-free expansion test of the total weathered disturbed expansive rock is obtained. When the dry density of the sample is high, the swelling deformation of the soil can be obviously divided into: initial slow expansion, accelerated expansion,When the dry density is small, the initial slow expansion stage and the accelerated expansion stage will be combined.At the same time, the larger the dry density, the longer it takes for the specimen to reach the stage of expansion and stability.Under any moisture content, the deformation of the specimen increases significantly with the increase of dry density.The effect of initial moisture content on the one dimensional expansion rate is greater than that of dry density.The effect of dry density on load-free expansion ratio is greater than that of moisture content.The relationship between the equilibrium expansion force and the dry density of the soil is exponential, and the expansion strain and the vertical stress are related to the logistic function.Based on the results of seven discriminant indexes, it is concluded that the fully weathered expansive rocks exposed on the surface of Jianshanying Bridge belong to strong expansive rocks.At the same time, the free expansion rate is the most accurate and efficient index for classification and discrimination of expansive rock.Based on the results of laboratory macro and micro tests, it is concluded that the expansion and shrinkage mechanism of fully weathered expansive rock is mainly based on diffusion double layer theory, supplemented by lattice expansion theory.The expansion mechanism of undisturbed expansive rocks is mainly considered by lattice expansion.
【学位授予单位】:西南交通大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:U442.2

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