IMHE OpenIR  > 山地灾害与地表过程重点实验室
都汶地区泥石流源地土物理力学性质研究
Alternative TitleRESEARCH ON PHYSICAL AND MECHANICAL PROPERTIES OF SOIL IN DEBRIS FLOW AT DU-WEN AREA
Language中文
陈星宇
Thesis Advisor苏立君
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name硕士
Degree Discipline岩土工程
Keyword泥石流源地土 剪切强度 渗透性 室内试验 原位测试
Other Abstract

泥石流源区广泛存在宽级配弱固结的碎石土,对泥石流启动机理的研究表明这种碎石土的物理力学性质在很大程度上决定了泥石流等灾害的易发性,其中剪切强度决定了泥石流爆发的临界值,而渗透性则决定了泥石流是否能够启动。因此本文通过选取都江堰-汶川地区典型的泥石流沟为研究区域,以室内试验和原位测试相结合的办法,得到源地土天然状态下的实际物理力学参数与相关性变化关系,为泥石流启动机理的研究与防灾减灾提供基础的参数支持。(1)对都江堰-汶川地区典型泥石流源地土进行原位水平推剪试验,得到试验区土石混合体的剪切破坏特征与抗剪强度值。试验结果表明含石量,天然密度,含水率以及试样尺寸对剪切破裂面的发展和强度值计算均有较大的影响,其中P5(颗粒粒径大于5mm含量)含量为试验关键性控制因素。原位推剪试验所得粘聚力相比室内直剪试验和三轴压缩实验所得参数值显著较小。(2)通过原位双环渗水试验,对汶川地区典型泥石流沟源地土进行了原位测试,得到了初渗率与稳渗率值。对张家坪沟源地土入渗过程分析表明试样颗粒粒径较大,块石含量较多,细颗粒含量较少,孔隙裂隙较为发育,土体结构较为松散,是该区域入渗过程中达到稳定渗流的时间较长,渗透率较大的主要原因。各区域渗透系数间的差异主要由土体结构,级配特征和物质来源不同所造成。国内外相关研究根据不同土体的入渗规律提出了Kostiakov模型,Horton模型和Philip模型,使用Kostiakov、Philip和Horton三种入渗模型对入渗过程进行拟合,结果表明Kostiakov模型相关性最好,能准确的反映源地土的渗透过程,同时Kostiakov模型参数计算表明,a值在26.62-65.94之间,表明入渗过程中渗透速率衰减较快。除张家坪沟外n值均大于0.4,表明入渗过程中土体结构变化较大,张家坪沟土体块石骨架作用较强,因此土体结构变化较小,较为稳定。(3)对试验区域源地土进行采样,分别测定其室内试验强度参数值,同时选取桃关沟为震后典型泥石流沟,采集源地土为实验对象,通过分析源地土的结构破坏模式,进行室内直剪试验和三轴剪切试验。直剪试验以含水率和干密度为变量,取源地土的粘聚力C和内摩擦角φ作为土体强度衡量指标进行实验。直剪实验结果表明,桃关沟源地土体的C值随干密度的增大而增大,随含水率的增大而减小,并且当含水率超过13%时,C值急剧降低;φ值则基本保持在31°左右,变化幅度不大。(4)通过开展不固结不排水三轴剪切试验,用实测的办法在不同轴向应变时对试样直径的增量进行量测。试验结果表明,剪切过程主要由体压缩阶段,鼓状变形阶段和剪切破坏面发展阶段组成,其中鼓状变形阶段是试验剪切过程的主要变形阶段。干密度的增加表现出试样的鼓状变形与剪切破坏阶段较为明显;含水率的增加提高了试样的塑性,增加了实测直径增量值;围压与端部效应共同作用,围压越大,鼓状变形越明显,实测直径增量就越大。通过形变特征计算剪切强度,分别以试样直径最大增量值和中部1/3部分平均直径值计算剪切强度,结果表明两者应力应变特征基本一致,但最大直径所得剪切强度值相对较小。

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Source region of mudslides widespread gravelly soil with poorly consolidated and wide grading.Research on the mechanism of debris flow indicates that physical and mechanical properties of this gravel soil largely determine the susceptibility of landslides and other disasters.Which shear strength determines the threshold of the outbreak of debris flow,and permeability determines whether debris flows can start.Therefore,this article selected typical debris flow in Dujiangyan-Wenchuan area as study area,getting the actual physical and mechanical parameters and correlation relationship between changes in laboratory and in-situ testing combined approach.So that we can provide fundamental parameters to support research on mudslide starting mechanism and disaster prevention and mitigationGetting the soil-rock mixture’s shear failure characteristics and shear strength values in Dujiangyan-Wenchuan test area by doing in-situ horizontal push-shear test.The results showed that the amount of rock containing,natural density,moisture content,and the sample size have a greater impact on the development of shear fracture surfaces and strength values calculated.Which P5 content are critical control factor.The results of in-situ push test indicate that cohesion are significantly smaller than direct shear test and triaxial compression resulting parameter values. doing in-situ test on typical debris flow source region soil by in-situ double ring infiltration test and getting the initial infiltration rate and the steady infiltration rate value.Zhangjiaping ditch source of soil infiltration process analysis show that large particle size of sample,big content of stone,small content of fine particle,developed porosity and fracture and loose soil structure is the main reason of large permeability and long time to achieve steady seepage.The main difference between the permeability coefficient is because of the soil structure,gradation characteristics and sources caused by different substances.Infiltration law studies at home and abroad proposed Kostiakov model,Horton model and Philip model according to different soil.Using three infiltration model to fit infiltration process,the results show that the process are best correlation with Kostiakov model which can accurately reflect the infiltration process itself.Meanwhile Kostiakov model parameters calculations indicate that a value between 26.62 to 65.94,which reflect the permeation rate decrease rapidly in the infiltration process,n value are greater than 0.4 without Zhangjiaping ditch,show that soil structure changes in the infiltration process.Zhangjiaping ditch soil’s effect of stone skeleton is stronger,so it’s soil structure is more stable than others.Sampling the sources soil to measured strength parameter values by laboratory tests.Selecting Taoguan ditch as the typical post-earthquake debris flow and collecting the source soil as experimental subjects.Doing indoor direct shear tests and triaxial shear test by analysing source of soil’s failure mode.Direct shear experiment varied by water content and dry density and take cohesion and internal friction angel as a measure of soil strength.The test results show that C value of Taoguan ditch source of soil with dry density increases and with the water content decreases.And when the moisture content exceeds 13%,C value drastically reduced;φ value is substantially maintained at about 31° with changed slightly.unconsolidated and undrained triaxial shear test was conducted with measured approach on the incremental sample diameter in different axial strain.The results showed that the shearing process mainly consists of body compression stage,drum-shaped deformation stage and shear failure surface development stage,of which the drum-shaped deformation stage is the main deformation stage of the shear process.Dry density increases showed the drum-shaped deformation and the shear failure stage are more obvious;The moisture content improve the plasticity of the sample,increasing the measured diameter increment value;The end-effect and the confining pressures are working together,the larger the confining pressure,the drum-shaped deformation are more obvious,and the measured diameter increment are bigger.Calculating the shear strength by deformation characteristics, respectively,with the sample diameter maximum incremental value and the central third of sample’s the average diameter.The results show that the stress-strain characteristics of both are basically the same,but the shear strength values obtained by the maximum diameter are relatively small.Key words:Source soil of debris flow;shear strength;permeability;laboratory test;situ testing. 

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18892
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
陈星宇. 都汶地区泥石流源地土物理力学性质研究[D]. 北京. 中国科学院大学,2016.
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