| 题名 | 基于土体含水量和实时降雨的泥石流预警指标研究 |
| 作者 | 马超 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 胡凯衡 |
| 关键词 | 泥石流 预警 临界土体含水量 地表径流 渐进式起动 整体起动 |
| 其他题名 | Study on forecasting index of debris flow prediction and forecasting method based on soil water content and real-time rainfall |
| 学位专业 | 岩土工程 |
| 中文摘要 | 对国内外对临界雨量研究成果进行总结，结合国内泥石流特征、形成模式分析表明单纯依靠临界雨量阈值的泥石流预警方法可能存在预警指标不足，判别条件单一，预警方法尚待优化或需要进一步考虑其他重要因子。对国内近年来泥石流有不同控制类型分析得出降雨引起含水量达到一定值以及产生一定水动力学强度的地表径流是主要原因。针对该含水量条件和地表径流条件，以蒋家沟为研究对象，分别展开模型试验和泥石流原型监测工作对其进行研究。主要内容如下： 1. 分析了国内外相关泥石流临界雨量阈值研究成果以及国内近年来泥石流灾害雨量特征、控制类型，明确了泥石流临界阈值并不是是绝对的一个值，而是一个区间。泥石流在不同的雨强条件下具有不同的起动模式和形成机理，其中最重要的是与降雨过程中能否形成一定深度的地下水有非常密切的联系。在总结国内外研究结果以及泥石流灾害特征基础上，指出单纯依靠临界雨量进行泥石流预警可能存在的问题。 2. 通过理论分析和人工降雨激发坡面土体失稳形成泥石流起动实验研究得到“渐进式”和”整体滑动“式两种起动方式，结合含水量和孔隙水压力数据分析了这两种起动模式的差别以及和内因。中等雨强条件下整体滑动起动方式源于土体内部整体形成了长时间的地下水水头，低雨强渐进式起动方式是由于土体内部整体无法形成一定厚度的地下水，高雨强无法形成一定厚度的地下水水头是由于地表径流强烈冲刷坡面物质使已经形成的地下水水头随即消失。渐进式起动方式中土体都没有达到饱和，整体滑动式土体达到饱和。渐进式失稳时孔隙水压力远小于整体滑动式失稳时孔隙水压力。 3. 通过人工降雨产流实验对泥石流源区土体地表径流产流机制进行了研究，分析了地表径流产生的过程和特点。主要包括在干燥条件和充分前期降雨条件下的地表径流形成过程；利用25°和30°两种坡度的产流结果探讨了地表径流流量与流深、流速之间的不同关系，以及地表水流剪切力、水流功率相互之间的关系。在考虑地表径流的坡面物源体稳定性分析表明，地表径流对坡面土体的稳定性影响非常明显，地表径流流速增加，径流提供的剪切力越大，安全性系数随剪切力递减。 4 通过泥石流形成原型监测系统，对低雨强、中等雨强和高雨强三种雨型降雨过程中孔隙水压力变化和泥石流形成进行初步分析：0~20cm土层是降雨入渗和蒸发的主要活动场所；低雨强和中等雨强条件下，20cm土层含水量发生变化需要约27mm的累计雨量。低雨强和中等雨强激发的泥石流可能与土体含水量超过土体失稳时含水量有关。高雨强条件下，孔隙水压力保持高值很长时间，可能与土体内部形成了一定水头的地下水以及产生了地表径流有关。 5 根据以上对降雨过程中土体失稳和产流的理论和实验结果分析，提出了基于土体含水量和实时降雨的泥石流预警方法，提炼了临界土体含水量条件（26%）和雨强指标关系式i_t≥f_p=(θ_n-θ_t│L)/?t，并对其物理意义进行了分析。结合蒋家沟2013年的三场泥石流进行了验算和结果分析，并与蒋家沟泥石流临界线和暴发线预测预报方程式进行了结果比对。结合实际的监测数据分析了这几场泥石流暴发的内因。 |
| 英文摘要 | This thesis firstly gave a brief historical over review on critical rainfall in debris flow forecasting all around the world and listed some characteristics of debris flows in I/D function, formation types in past few years of China. Previous work pointed that it is necessary to predict debris flow with much more parameters as soon as possible other than single critical rainfall. Two debris flow formation types: antecedent rainfall-dominated and short-duration dominated tell us that both of soil moisture and surface runoff generation are important in debris flow formation. Then, we taken Jiangjia Ravine as object and conducted researches on the two parameters by artificial rainfall experiments and field monitoring. The main contents are listed as follows: 1 The critical rainfall index is not a constant number other than an interval related to rock types, physical geography features in a watershed. Historical researches in debris flow initiation mechanics mainly focused on the rising water table conditions during rainfall. The previous work and analysis on recent debris flows characteristics revealed that much more parameters should be used in debris flow prediction other than single critical rainfall. 2. Retrogressive and complete failure were concluded by three artificial rainfall experiments under rainfall intensity of 5.6, 9.9 and 16.mm per 10 minutes referring to the typical landforms and physical features of material resources in upstream of Jiangjia Ravine.The retrogressive initiation style occurred when soil moisture and pore water pressure flashed from zero then vanished afterwards, which tell us there was no complete water table interior soil mass. Complete failure style occurred when soil moisture kept at saturation degree and pore water pressure kept at a higher value for a long time than retrogressive style. Therefore, complete failure occurred with rising, long-duration water table in soil mass when rainfall intensity is 9.9mm/10min. The reason why retrogressive failure occurred in experiments of rainfall intensity 16.3mm/10min lies in surface runoff washed the superficial materials causing the water table level reaches to surface and flow away. 3. Dynamics features and related parameters of surface runoff were analyzed by rainfall experiments under slope gradient of 25 °and 30°. The discharge remains as a constant values no matter the soil mass was dry or wet. The velocity correlates positively with discharge under slope gradient of 30° while height of surface runoff keeps relatively constant. On the contrary, the height of surface runoff correlates positively with discharge while the velocity keeps relatively constant. The instinct relationships between rainfall intensity, discharge, shear force power, the Froude and Reynolds number were also analyzed. The limit equilibrium analysis considering influence of shear force of surface runoff revealed that the surface off can generate a great act on stability of superficial soil mass. The stronger the shear force is, the smaller the factor of safety decrease. 4 We conducted preliminarily analysis on three debris flow events triggered by lower, moderate and high rainfall intensity respectively, as well as the correlation between pore water pressure and rainfall. The soil mass above 20cm act most actively in rainfall infiltration and evaporation than that below 40cm. The soil moisture in soil mass above 20cm can increase under lower and moderate rain when accumulated rainfall approximately equals to 27mm on condition that the soil mass is extremely dry. Two debris flow events triggered by lower and moderate rainfall may correlates to soil failure. The debris flow triggered by high rainfall may correlates to long-duration high pore water pressure and surface runoff generation. 5 By results from artificial rainfall experiments of debris flow initiation and surface runoff generation with help of theory analysis about limit equilibrium analysis, a new debris flow forecastin |
| 语种 | 中文 |
| 公开日期 | 2015-03-03 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/7870]  |
| 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 | 马超. 基于土体含水量和实时降雨的泥石流预警指标研究[D]. 北京. 中国科学院研究生院. 2014. |
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