粘土颗粒含量对蒋家沟泥石流启动影响及成灾机理研究

蒋家沟泥石流土属宽级配砾石,粒径大小悬殊,其中粘土颗粒含量虽不多,却因其巨大表面积和亲水性,明显地影响着泥石流的启动,级配对泥石流启动灾变的影响研究对于探索泥石流的启动机理意义重大。本文以蒋家沟泥石流土为研究对象,通过深入蒋家沟流域现场调查、收集资料和基本物理化学试验,以机动灵活、试验条件易于控制的室内模型试验为基础,对影响泥石流启动的相关因素进行了探讨,采用三轴试验仪研究了蒋家沟泥石流土的力学特征,解释试验现象,并通过突变理论建立了泥石流启动的模型。将试验结果与现场现象结合起来探索泥石流的破坏模式和启动成灾机理。主要研究内容如下：1.对蒋家沟地形、地质、地貌等进行调查和统计分析,揭示了其岩土体特殊的发育环境和形成泥石流得天独厚的条件。2.运用先进的实验设备对蒋家沟泥石流土的基本物理化学特性进行了研究,揭示其主要粘土矿物成分、化学成分、级配特征、ESP值、分散度、渗透特性、地下水矿化度、硬度等特殊性质,分析了这些特殊性质与泥石流形成的内在联系。3.对三种级配的蒋家沟泥石流土超径部分等量替换处理后进行三轴剪切试验。在CU、UU试验结果基础上,分析了土样的应力-应变、孔隙水压力以及应力路径特征；得出了不同密度、不同粘粒含量下的土样抗剪指标,并拟合出相应的关系式,试验结果用于理论分析和解释模型试验现象。4.通过自行设计的模型槽在室内进行了泥石流启动模型试验,研究了不同粘土颗粒含量、不同干密度、不同降雨强度、不同堆积坡度下的泥石流易发性问题,同时研究了粘土颗粒含量的临界性问题和迁移对泥石启动的影响。在模型试验研究中引“入渗比”概念,研究了入渗比与泥石流易发性的相关性。5.通过分析物化试验、三轴试验、模型试验现象,得出泥石流破坏形成的五个阶段,泥石流在粘粒多、大雨强和粘粒少、中小雨强下的破坏模式和启动灾变机理。6.结合试验结果与泥石流的突发性,采用突变理论建立了泥石流边坡突变破坏模型,并通过试验得出的粘粒含量、干密度、含水量与抗剪强度的关系式,将上述影响因子嵌入模型,提高了模型的适用性。这为泥石流的预测预报研究及区域危险性评价工作提供了理论支持。
电加热器


According to the grain size of debris-flow soil in Jiangjia Ravine, it’s gravel soil with wide grain size, though clay particles content among it was not much, the initiation of debris-flow is obviously impacted by it because of its huge surface area and the hydrophilic. Graduation of soil for debris-flow initiation is very important for exploring the catastrophe mechanism of debris-flows. Debris-flow soil in Jiangjia Ravine is regarded as subject investigated in the paper, the factors impacting the initiation of debris-flow are studied by investigation, collection of information, physical and chemical experiment, indoor model experiment. the mechanical behavior of gravelly soil is studied by triaxial test, some experiment phenomena is explained, initiation model of debris-flow is established by mutation theory. Experimental results and on-site phenomena are combined, failure pattern and catastrophe mechanism of debris-flows are explored. The main research content is as follows:1. Topography, geology, geomorphology in Jiangjia Ravine is investigated and statistically analyzed, its special development environment and exceptional conditions for the formation of debris-flows are disclosed.2. the physical and chemical properties of soil in Jiangjia Ravine are studied by sophisticated equipment, clay mineral composition, chemical composition, grain size, ESP(Exchangeable Sodium Percentage), dispersion degree, seepage characteristic, the salinity and hardness of groundwater are included. The internal links between initiation of debris-flow and the properties mentioned above.3. Three type of samples were treated by equivalent substitution of grain diameter before triaxial test. Based on the result of different density, different graduation under undrained condition, the character of stress-strain, pore-water pressure and stress path are analyzed, index of shear strength and relational expression in different density, different graduation are obtained, they can be used for theoretical analysis and model experiment explaining.4. Susceptibility of debris-flows in different graduation, different density, different rainfall intensity, different slope angle are studied by self-designed model groove. meanwhile, the criticality of clay particles content and the impaction of grain migration for debris-flow initiation are studied. The "influent ratio" is introduced in model test and the relationship between "influent ratio" and susceptibility of debris-flows is studied.5. the formation process of debris-flow are divided into five stage by model test, physical and chemical test, triaxial test. The failure pattern and catastrophe mechanism of debris-flows are studied in condition of much clay particles, strong rain and few clay particles, weak rain.6.Combining the experiment results and the sudden breakout of debris-flow, the failure model are founded by mutation theory, the relational expression between shear strength and clay particles content, dry density and water content that obtained by experiment is embedded into the model, the applicability of it is improved. It provides theoretical support for debris-flow predictio