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砾石土级配特征对坡面泥石流启动的临界雨量影响研究
Alternative TitleExperimental Research on the Relationship between Gravel Soil Grade and Critical Rainfall of Debris Flow Initation
Language中文
贺拿
Thesis Advisor陈宁生
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline岩土工程
Keyword坡面泥石流 砾石土 分维值 渗透系数 人工降雨试验 临界雨量
Abstract坡面泥石流占泥石流总数的90%以上,坡面泥石流造成的损失居高不下。坡面泥石流具有点多、面广、暴发突然等诸多特点,采取工程措施进行综合防治在短期内难以实现。结合各区域泥石流的形成特点,探讨泥石流形成的模式及机理,在此基础上通过数据分析,探讨各区域泥石流源区砾石土在不同的工况(不同的降雨强度)下泥石流启动的临界雨量,不仅有助于防灾减灾,又可以为泥石流的预测预报提供重要参考。 本文以四川宁南与云南巧家交界的区域作为研究区,通过对中国18个大型泥石流灾害重点规划和治理区内的116条泥石流沟进行野外调查,获取区域的基础资料及各区域土体的物理特征(密度及含水率等)。通过野外取样、室内颗分试验,分析各区域砾石土的物质组成特征,建立粒度特征数据库;在此基础上引入分形理论计算各土样的分维值,以分维值表征砾石土的级配特征,比较不同区域泥石流源区砾石土级配特征的共性及差异,建立分维值数据库;基于泥石流源区砾石土的分维值特征,通过直剪试验、常水头渗透试验及野外人工降雨试验,分析砾石土强度、渗透系数及临界雨量与其分维值之间的关系,综合分析后得到以下成果: (1)通过野外取样、室内颗分试验及分形理论计算后发现,泥石流源区砾石土以一重分形特征为主,一重分形土样占样本总数的88.46%,一重分形土样分维值介于2.25~2.798,分维值最大的为蒋家沟土样,最小的为干溪沟土样,分维值介于2.4-2.7之间的土样130个,占一重分形总数的80.75%。 (2)对直剪试验的结果分析后发现:强度随着分维值的增大而减小。 (3)以自制的常水头渗透试验装置进行渗透试验,对试验数据分析发现:砾石土分维值与渗透系数具有较好的相关性,经多元回归分析建立渗透系数与干密度及分维值之间的函数关系: 渗透系数与分维值及干密度之间具有较好的幂函数关系;分维值相同时,渗透系数随干密度的增大而减小。 (4)选择典型区域开展野外人工降雨泥石流启动试验,对比各分维值条件下泥石流启动的难易程度、启动的特点、启动时间及规模,对比可知:分维值较小的砾石土在降雨过程中不易形成泥石流。在相同的降雨条件下,随之分维值的增加砾石土形成泥石流所需的时间逐渐减小,分维值小于2.4时砾石土形成泥石流的临界雨量值更高。对启动形成泥石流的各组试验推算其10分钟及1小时临界雨量,并分析10分钟及1小时临界雨量与分维值之间的相关性,分析发现:分维值与10分钟临界雨量及1小时临界雨量相关性较显著,分维值与10分钟及1小时临界雨量之间有较好的指数关系,相关公式分别为: (10分钟临界雨量公式); (1小时临界雨量公式),式中: 及 为泥石流启动的10分钟及1小时临界雨量, 为砾石土分维值。
Other AbstractSlope debris flow account for 95% of the total debris flow events and caused heavy casualties and a great number of economic losses. Slope debris flow distributed widely not only in our country but also worldwide, due to the current economic situation, comprehensive engineering measures to cope with slope debris flow disasters is impossible. Combined with the characteristics of the valley such as solid materials, geographic and geomorphic conditions and meteorological conditions to discuss the mode and mechanism of debris flow, on the basis of the aforementioned research further discusses the critical rainfall of debris flow under different rainfall conditions, thus in turn will be conductive to both disaster prevention and mitigation and provides valuable reference for debris flow prediction. This research takes one typical area (border area between Sichuan province and Yunnan province) from 18 large debris flow planning and management areas as study area and obtained the basic data and the physical characteristics of the soil through vast field investigations. Through sampling and screening of the soil samples we analyze the particle size distribution of the gravel soil, and establish granularity characteristic database. Then use fractal theory to calculate the fractal dimension of the gravel soil, and adopt fractal dimension to represent particle size distribution of the gravel soil, based on the data of fractal dimension compare the similarity and discrepancy of gravel soil in different gullies. On the basis of these data we conducted direct shear test, constant head permeability test and field artificial rainfall experiment to probe into the relationship between fractal dimension and gravel soil strength, permeability coefficient and critical rainfall of debris flow initiation. After comprehensive analysis we acquired the following achievements: (1) Through sampling, screening and fractal theory calculations we found that the gravel soil is mainly concentrated in one fractal dimension, the samples of one fractal dimension account for about 88.46% of the total samples and one fractal dimension value ranges from about 2.25 to 2.798. The samples of maximal fractal dimension and the minimal fractal dimension are Jiang jia gou gully and Gan xi gou gully respectively. The number of soil samples whose fractal dimension value ranges from about 2.4 to 2.7 is about 130, account for 80.75% of the one fractal dimension soil samples. (2) Analyzing the results of direct shear test we know that soil strength decreased as fractal dimension increased. (3) We conducted penetration test by means of self-made constant head permeability test device, by analyzing the data of the experiment we find that fractal dimension and permeability coefficient is significant correlated, by multiple regression analysis established the function between permeability, fractal dimension and soil dry density as following: This function signified that permeability coefficient has a good power function with fractal dimension and soil dry density. Under same fractal dimension, permeability decreased as soil dry density increased. (4) Artificial rainfall experiments were conducted in typical area. By comparing the phenomenon and results of debris flow initiation we know that for gravel soil with lower fractal dimension it is impossible to initiate debris flow under intense rainfall. Under same rainfall conditions, the triggering cumulative rainfall is decreased with the fractal dimension increased, moreover, the critical rainfall for gravel soil whose fractal dimension value is less than 2.4 is much higher. We calculated the 10mins cumulative rainfall and 1hour rainfall respectively, through calculation and fitting we acquired that the relationship between fractal dimension, 10mins cumulative rainfall and 1hour rainfall is significantly correlated, fractal dimension has good exponential relationship with 10mins cumulative rainfall and 1hour rainfall, the correlatio
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7837
Collection山地灾害与地表过程重点实验室
Recommended Citation
GB/T 7714
贺拿. 砾石土级配特征对坡面泥石流启动的临界雨量影响研究[D]. 北京. 中国科学院研究生院,2014.
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