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题名	泥石流源区砾石土粒度分形特征对物理力学性质的影响
作者	黄祺
学位类别	硕士
答辩日期	2013
授予单位	中国科学院研究生院
授予地点	北京
导师	陈宁生
关键词	泥石流 砾石土 颗粒组成 粒度分形 力学性质
其他题名	Particle Size Fractal Characteristics of Gravel Soil in Debris Flow Original Area Impact on Mechanical Properties
学位专业	建筑与土木工程
中文摘要	我国泥石流主要物质来源于一种宽级配的砾石土，土体颗粒组成是土体的自然属性，颗粒组成对泥石流启动和易发性有重要影响，因此，研究砾石土颗粒组成特征及对其力学性质的影响有重要意义。本文以勘查过的19条泥石流沟源区砾石土体的颗分数据为基础，引入分形理论研究砾石土颗粒组成特征。利用三轴试验、渗透试验、湿陷试验研究了不同粒度分维值砾石土体的力学性质，运用土力学理论、分形理论解释试验现象。依据试验结果对泥石流土体进行了简单地分类。取得了以下几点成果： （1）泥石流源区砾石土体具有一重、二重和三重分形特征，以一重分形特征为主；一重分形特征的砾石土各粒组含量连续性较好，二重分形表明某一粒组含量存在突变；研究的沟道砾石土的平均粒度分维值在2.45~2.78之间，粒度分维值随粘粒含量增加而增大。 （2）试样的湿陷性随粒度分维值的增大先增加后减小，在2.60~2.70的试样湿陷性较大。不同粒度分维值的试样都表现为剪缩型破坏，2.30~2.70的试样应力~应变曲线为应变软化型，在轴向应变ε<3%时就达到应力峰值；2.75~2.80的试样为应变硬化型，其孔隙水压力峰值对应的轴向应变ε<5%。破坏时对应的偏应力(σ1-σ3) 、剪应力τ，随粒度分维值增大先增加后减小再增加，2.60或2.65最低；而孔隙水压力为先增加后减少，大于2.55的试样孔隙水压力相差不大。粘聚力C(C＇)随粒度分维值增大先减小后增大，在2.6或2.65最小，内摩擦角φ(φ＇)总体上表现为随粒度分维值增大而减小的趋势。 （3）渗透系数随粒度分维值增大呈负指数形式减少；土体孔隙率随粒度分维值增大而增大；粒径对渗透系数的影响大于孔隙率的影响。 （4）综合不同粒度分维值砾石土体的力学特征，其分为三类：一是粒度分维值在2.55~2.70尤其2.6~2.65的砾石土体易失稳破坏；二是粒度分维值在2.50~2.55、2.70~2.75的砾石土体属于较易失稳破坏；三是粒度分维值大于2.50和大于2.75砾石土体不易失稳破坏。
英文摘要	The wide graded gravel soil is the main soil source for debris flows in China. The distribution of particle size is the native property for soil, which haves significant influence on debris flow initiation, leading to being meaningful for studying on the particle composition and its impact on the mechanics. Based on the particle composition from the investigated 19 debris flow gullies, the fractal theory is adopted to study on the particle composition of gravel soil in this thesis. Then, triaxial test, penetration test and collapse test, with gravel soil of different dimension values, are used to test the mechanical properties; and soil mechanics and fractal theory are applied to discuss the phenomenon in the tests. At last, the gravel soil source is classified into categories. The main results are as follows： (1) The gravel soil possesses the characteristic of fractal, and mainly in one dimension fractal; particles with one dimension fractal is fine graded, particles with two dimension fractal is weak graded with existing a particle abrupt; the average value of particle size fractal is between 2.45 and 2.78 in the 19 debris flow gullies, and it goes up with the increasing of clay content. (2) The sample collapsibility firstly goes up then decreases with increasing of particle size fractal values, the collapsibility of 2.6~2.7 samples are bigger. All samples presents contraction under shear. The stress-strain curves of 2.3~2.7 samples are softening, the axial strain is less than 3% when the soil reached the peak stress; that of 2.75and 2.8 samples are the hardened, the axial strain is less than 5% when the peak pore water pressure appears. The deviatoric stress, shear stress of soil failure primarily rises and decline and then increases again with the increasing of particle size fractal values, those of 2.6 or 2.65 samples reach minimums. Increasing of particle size fractal values, the pore water pressure firstly increases and then falls, those of samples (D>2.55) are a small difference. The cohesive force C (or effective cohesive force C＇) firstly decreases then increase, the minimums appear in 2.6 or 2.65 samples, the whole trend of internal friction angle decreases with increasing of particle size fractal value. (3) The relationship between the permeability coefficient and particle size fractal value shows a negative exponent relation. The soil porosity increases along with increasing of particle fractal values. The influence of particle size on the permeability coefficient is greater than that of the porosity. (4) According to the mechanical characteristics of different particle size fractal value gravel soil, the gravel soil is divided into three categories: the gravel soil of 2.55~2.70 especially 2.60~2.65 is more favorable to instability and failure, that of 2.50~2.55 and 2.70~2.75 is favorable, the rest of gravel soil is difficult.
语种	中文
公开日期	2014-08-26
内容类型	学位论文
源URL	[http://ir.imde.ac.cn/handle/131551/7138]
专题	成都山地灾害与环境研究所_山地灾害与地表过程重点实验室
推荐引用方式 GB/T 7714	黄祺. 泥石流源区砾石土粒度分形特征对物理力学性质的影响[D]. 北京. 中国科学院研究生院. 2013.

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