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泥石流源区松散土级配对抗剪强度的影响
Alternative TitleAffect of Grain Composition on the Shear Strength of Wide-grading Loose Soil in Trigging Area of Debris Flow
Language中文
孔应德
Thesis Advisor崔鹏
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name硕士
Degree Discipline建筑与土木工程
Keyword宽级配弱固结土 三轴剪切实验 颗粒级配 细颗粒分界 抗剪强度
Abstract泥石流源区松散土大多是一种宽级配弱固结土,土体抗剪强度是泥石流起动机理研究的重要组成部分。泥石流起动模型研究中发现土体颗粒级配,尤其是细颗粒对宽级配弱固结土失稳形成泥石流的影响很大。目前室内实验对泥石流物源土天然级配特征、细颗粒影响土体抗剪强度方面还有待进一步的研究。 考虑不同地质成因物源土在级配方面的差别,本研究选取不同地质成因的泥石流物源,通过粒度分析实验和三轴强度实验分析土体级配对土体抗剪强度的影响;另外,考虑自然界级配种类多样,典型的五类泥石流物源级配的研究不足以反映自然界物源土的级配特征。因此本研究探讨了一种新的细颗粒分界方法,在此基础上选取典型千枚岩母质和泥质灰岩母质的坡积物,进行细颗粒含量配比影响强度实验。通过研究,得出的初步结论如下: (1)泥石流源区松散土级配对土体抗剪强度c、φ值和孔隙水压力系数A有重要的影响。基于天然物源土体的级配特征,用分维值D表征其细粒部分(包含粘粒、粉粒、沙粒)特征,标度分布参数Dc表征土体粗粒部分特征。分析得到:泥石流源区松散土粘聚力c与细粒部分存在指数相关,土体内摩擦角φ与标度参数Dc符合线性相关,拟合实验数据得到粘聚力C值与分维值D之间满足:c=0.00137exp(3.686D),相关系数0.9518;φ值与反映粗颗粒标度分布参数Dc满足: φ=0.5038Dc+15.52,相关系数0.9738。相同围压下,孔压系数A随着细粒部分的增加,呈增长趋势。 (2)不同母岩产生的土体,级配特征不同,具有不同的细颗粒分界粒径。母岩岩性偏硬的土类,细颗粒分界粒径较小,如花岗岩质为0.25mm;母岩硬度稍低的土类分界粒径角大,大都为1mm。 (3)基于本研究的细颗粒分界方法,细颗粒含量(质量百分比)在一定的变化区间对土体抗剪强度影响较大,这主要取决于细颗粒对粗颗粒构成的孔隙的充填程度。细颗粒含量从12~32%时,粘聚力c值增长明显;细颗粒含量22~42%时,摩擦角 值快速降低;随着细颗粒含量的增加,孔隙水压力系数A,先增大后减小,转折点在32~42%之间。 (4)千枚岩质和泥质灰岩质泥石流物源,细颗粒(1mm以下)含量32~42%时,土体强度降低明显。自然界中在这种情况下,代表了土体容易失稳形成泥石流情况。
Other AbstractMost material source of debris flow is wide-grade-unconsolidated soil, whose soil shear strength is an important part of the researches in the initiation of debris flow. Researches on the model of the initiation of debris flow have discovered that the grain composition, especially the fine particle, has a big effect on the debris flow’s initiation from the wide-grade-unconsolidated soil. Now, more researches on the affect of grain composition, especially the fine particle on the soil shear strength of the wide-grade-unconsolidated soil by the laboratory experimentation are needed. This study chooses different geologic origin substance source of debris flow and researches the affect of the total grain composition on the soil shear strength by grading analysis experiment and triaxial strength experiment. And also different lithological substance source of debris flow are chosen to definite the fine particle size of the grain boundary, considering the mineral composition and content in the fine particle. At last, we study on the affect of the content of fine particle on the wide-grade-unconsolidated soil shear strength by choosing the Phyllite and Argillaceous limestone lithology slope wash soil as the typical slope wash. The main research work and its achievements involve several aspects as follows: (1) The grain composition of loose substance source soils of debris flow have an important effect on the parameter of soil shear strength (c、φ ) and the pore pressure parameter (A). According to the grain composition of natural substance source, the fractal dimension D is used standing for fine particle of the soil (including clay, silt, and sand), and the parameter of scaling distribution Dc is used standing for coarse sand. Through the analyzing of the slumped mass, the residual deposit, the gully bed material, the glacial till and the loess, the relation between cohesive force C and fractal dimension D meet:c=0.00137exp(3.686D), R2: 0.9518. The relation between frictional angle φand the parameter of scaling distribution for grain composition meet:φ=0.5038Dc+15.52, R2: 0.9738. Under the same confining pressure, the pore pressure parameter A increases with the increase of fine particle content. (2) Soil from different parent rock have different grain boundary of fine particle. For soil from hard parent rock, the grain boundary of fine particle is much smaller, for example, 0.25mm for granite soil. For soil from soft parent rock, they tend to have a uniform grain boundary of fine particle, 1 mm. (3) The change of the content of fine particle has a great effect on shear strength of the loose substance source soils of debris flow, which is mainly determined by the filling degree of fine particle to the pore formed by coarse particle. When the content of fine particle range from 12~32%, cohesive force C increases rapidly. When the content of fine particle range from 22~42%, frictional angle drops down. When the content of fine particle increase, the pore pressure parameter A firstly turn down, then turn up, the turning point of the content of fine particle appear at 32~42%. (4) For Phyllite and Argillaceous limestone lithology substance source of debris flow, Soil shear strength drop down when the content of fine particle between 32% and 42%. It is most likely to motivate a large-scale debris flow. Keywords: Wide-grade-unconsolidated soil, Triaxial strength experiment, Grain composition, Fine particle size of the grain boundary, soil shear strength.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7822
Collection山地灾害与地表过程重点实验室
Recommended Citation
GB/T 7714
孔应德. 泥石流源区松散土级配对抗剪强度的影响[D]. 北京. 中国科学院研究生院,2014.
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