| 题名 | 汶川地震灾区震后泥石流起动临界阈值研究 |
| 作者 | 方华 |
| 学位类别 | 博士 |
| 答辩日期 | 2012-05-20 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 崔鹏 |
| 关键词 | 汶川地震 泥石流 形成条件 力学性质 人工降雨原型试验 临界条件 阈值 |
| 其他题名 | Research on the Critical Threshold Value of Debris Flow in the Wenchuan Earthquake-Stricken Area after the Earthquake |
| 学位专业 | 岩土工程 |
| 中文摘要 | 本文以汶川地震极重灾区为主要研究区，在广泛调阅国内外文献资料和大量野外调查的基础上，总结分析震后泥石流成灾条件和形成条件的变化；选择典型泥石流沟谷源区土体开展室内力学试验，研究地震极重灾区泥石流源区砾石土体的物理力学性质，结合震后大量堆积砾石土体特定的物理力学性质和泥石流成灾条件，选取典型研究区域进行野外原型泥石流起动人工降雨试验，分析试验研究区松散堆积砾石土体起动形成泥石流的临界阈值条件，结合室内实验结果以及历史泥石流灾害降雨资料等，提出震后灾区松散土体破坏起动时的土体含水量、孔隙水压力以及降雨量等特征阈值，为泥石流监测预警提供服务。主要研究内容和结论如下：（1）震后泥石流的发育环境背景条件发生了显著的变化，主要表现在地质灾害发育，植被破坏严重，流域微地貌变化明显和水文条件发生的变化。（2）对地震灾区典型泥石流沟谷源区砾石土体级配、密度和含水量等结构特征进行分析。结果表明地震崩塌滑坡堆积砾石土体砾石含量高达40%以上，粘粒含量基本都小于2%；土体的天然密度为1.6-1.8g/cmP3P，干密度介于1.5-1.6g/cmP3P之间；天然含水量位于6%-11%之间，土体含水量沿深度变化明显，超过20cm深度土体含水量明显减小，土体深部含水量变化情况主要受其结构和渗透性的影响。（3）对典型泥石流沟谷源区砾石土体进行不同含水率、不同干密度直剪强度特征的试验研究。建立了砾石土强度与含水率以及干密度的关系，土体干密度（密实度）对其抗剪强度影响很大，在相同密度条件下，当土体含水量达到15%后，土体的抗剪强度迅速降低，处于失稳的临界状态。（4）选择重点典型区域松散堆积砾石土体进行大型原型野外人工降雨泥石流起动试验，分析同一初始含水量和密度状态条件下，砾石土体对不同降雨强度的响应变化。历次人工降雨试验土体大规模破坏形成泥石流时的含水量基本呈平稳趋势，土体孔隙水压力伴随泥石流的形成过程具有明显的陡涨陡落过程，并且随雨强的增大略显增长趋势，土体大规模破坏起动形成泥石流所需的时间随降雨强度的增加呈现明显减小趋势。（5）将地震灾区典型泥石流沟砾石土物理力学性质试验结果，与泥石流起动人工降雨原型试验过程现象及数据结果和震后泥石流历史降雨数据进行综合对比分析，分析了试验研究区泥石流起动临界条件，并给出相关监测预警阈值。 |
| 英文摘要 | Taking the earthquake stricken area as the main study area, this dissertation mainly discussed disaster and formation characteristics, critical conditions and the threshold value of gravelly soil failure and debris flow initiation after the earthquake based on field survey, laboratory and field tests and debris flow historical data analyse. The main research work and its achievements of this study involves several aspects as follows: (1)The development environment background conditions had significantly changed after the earthquake, which mainly manifested in: serious damage to the vegetation, obvious changes in the watershed microrelief and changes of hydrological conditions. (2)The Hstructural characteristicsH of earthquake triggered gravelly soil including HgradationH, density and water content were tested for the following direct-shear strength test, triaxial test and artificial rainfall prototype test. The earthquake triggered gravelly soil are typical wide-graded soil, with up to 40% portion of gravel and less than 2.0% clay; the average natural density of the gravelly soil is 1.6-1.8 g/cmP3P, Hdry densityH is between 1.5-1.6 g/cmP3P; natural water content varies from 6%-11%, the water content changes significantly along the depth, that the water content is much reduced since the soil is in more than 20 cm depth, the water content of deep soil is mainly influenced by the soil structure and its penetrability which changes with the lithology. (3)The direct-shear and triaxial strength behavior of original samples with different water content and dry density were tested to establish the relationship between direct-shear strength and wate content and dry density. The soil dry density(compactness) is much important to the soil shear strength; under the same dry density, the soil shear strength Hdecreased rapidlyH with the water content up to 15%, that the soil is in the critical state of instability. (4)The field artificial rainfall prototype initiating tests of debris flow to the loose deposits in typical debris flow area(the Huashiban gully) were carried out to Hobserve and analyzeH the HresponseH of gravelly soil with same initial water content and density to different rainfall intensity. The gravelly soil failure water content do not increased with the increase of rainfall intensity, but the obviously decreased of initiation time with the increase of rainfall intensity, and the pore water pressure has obvious rapid growth and rapid reduction process accompanied with the formation of the debris flow. (5) The mechanical behavior of gravelly soil，the critical phenomenon in process and data results of debris-flows initiation test and the debris flow historical rainfall data are analyzed relatively, in order to explain the mechanism of failure and critical condition of debris-flows under different action, and proposed the relevant threshold value for the debris flow monitoring and early warning system in the study area. |
| 语种 | 中文 |
| 公开日期 | 2013-01-11 |
| 内容类型 | 学位论文 |
| 源URL | [http://192.168.143.20:8080/handle/131551/4802]  |
| 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 | 方华. 汶川地震灾区震后泥石流起动临界阈值研究[D]. 北京. 中国科学院研究生院. 2012. |
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