沟谷型泥石流规模频率关系及其在城镇危险区评价中的应用 | |
Alternative Title | Magnitude-frequency Relationship of Valley-type Debris Flows and Its Application in Hazard Zonation |
高延超 | |
Subtype | 博士 |
Thesis Advisor | 陈宁生 |
2018 | |
Degree Grantor | 中国科学院大学 |
Place of Conferral | 北京 |
Degree Discipline | 岩土工程 |
Keyword | 泥石流 规模 频率 危险性 地震 |
Abstract | 泥石流规模与频率是泥石流预警预报与防治工程的重要参数和主要依据。受限于观测数据较少，相关研究的进展比较缓慢。中低频率的泥石流峰值流量计算，在过去的工程实践和灾害防治中主要采用暴雨泥石流同频率的配方法，但在汶川震后的极震区，由于松散物源的大量增加，泥石流的规模与频率都发生了较大变化，配方法的计算结果小于实测值。为解决这一问题，本文分析云南东川蒋家沟长期监测的泥石流观测数据，对丰富物源区的高频率泥石流进行研究。通过对蒋家沟1987-2004年间的178次泥石流事件的累积频率-规模关系进行非线性回归分析，得到y=a-b×ln(x+c)的对数函数关系。为了验证这种规律，将甘肃武都的火烧沟、柳湾沟、泥湾沟和云南大盈江的浑水沟进行了相同的分析，发现这四条沟道的规模-频率关系也符合对数函数关系。但五条沟道的a、b、c三个常数的差异较大。在物源丰富的情况下，泥石流规模更多地受控于流域特征及降雨特征。本文用流域面积和最大日降雨量这两个指标对上述三个常数采用回归分析，得出3个常数与流域面积和最大日降雨的关系式。强震区沟道内的物源在短时间内的大量聚集，导致泥石流活动剧烈，表现出高频率的特征，适用于本文分析的这种对数函数关系。随着沟道内松散物源的减少与固结，泥石流的规模与频率关系开始向着低频率的方向变化。本文作者对鲁甸地震区、芦山地震区及汶川地震区的震后松散砾石土随时间自然固结，颗粒级配、干密度、抗剪强度等指标进行野外及室内实验。总体而言，随着震后松散土体的固结，土体的颗粒级配发生变化，细颗粒流失；土体的干密度增大，孔隙比降低。土体的内摩擦角φ与粘聚力c均随固结增长，土体的抗剪强度也随之增大。随着泥石流物源减少，启动难度增加。从土体强度恢复的曲线来看，震后泥石流的活跃周期约为15-25年。为了验证这一规律，本文进一步研究了震后的成都龙门山地震区内龙溪-白沙河流域的的剥蚀数据的衰减规律，从另一个角度得出震后的泥石流活跃周期为26年。因此本文推荐在震后25年内的极震区泥石流流量计算宜采用统计公式法，25年之后采用雨洪配方法。为验证统计公式法的适用性，针对地震高发的康定城区子耳沟，分别采用了统计公式法与进行了配方法不同频率的峰值流量计算与危险区范围数值模拟。结果显示，在同等频率下，统计公式法得到的泥石流峰值流量远大于配方法；统计公式法5a一遇的峰值流量与配方法100a一遇的计算结果相近。这和汶川地震后极震区内的泥石流较一致，5-20a一遇的暴雨可能诱发100a一遇规模的泥石流。对于新构造运动强烈的重要城镇及重要工程，泥石流的工程建设及防灾减灾更推荐使用统计公式法。 |
Other Abstract | The magnitude-frequency relationship of debris flows is the basis for engineering designs and risk assessments. However, because of the lack of debris flow monitoring data, research progress in this area has been relatively slow. In conventional engineering practice and disaster prevention and reduction, the calculation of the peak discharge of debris flow is calculated using the method of matching the water and debris flow with the same frequency. However, in the debris flow in the Wenchuan earthquake-stricken area, due to the drastic increase in the loose source, the debris flow magnitude and frequency of calculations exceed the results of this method.The MF relationship of debris flows in an area with sufficient sources is evaluated based on a regression analysis of 178 debris flow events that occurred from 1987-2004 in Jiangjia Gully, Yunnan Province. The magnitude-cumulative frequency relationship of the Jiangjia Gully debris flows is consistent with the linear logarithmic transformation function. Moreover, the observation data of debris flows in Hunshui Gully of Yunnan Province and Huoshao Gully, Liuwan Gully, and Niwan Gully of Gansu Province are used to verify the function. The results showed that the MCF relationship of high-frequency debris flows is consistent with the power law equation, although the constants a, b and c in the equation are considerably different. Further analysis showed a strong correlation between the differences in the constants and the drainage area and daily maximum precipitation. With abundant sources, the characteristics of debris flow are more controlled by basin characteristics and rainfall characteristics. In order to analyze this difference, we use the two indicators of drainage area and maximum daily precipitation to apply the regression analysis to the above three constants to obtain the relationship between the three constants and the basin area and the maximum daily rainfall.The source of material in the channel of the strong earthquake area gathers in a large amount within a short time, and the debris flow activity begins to be strong, showing the characteristics of high frequency, and is suitable for the power-law relationship analyzed. In this paper, field and laboratory experiments were performed on the loose aggregates, particle size distribution, dry density, shear strength, and other indicators of loose gravel soil in the Ludian, Lushan and Wenchuan earthquakes with the post-earthquake time. In general, with the consolidation of loose soil after the earthquake, the particle size distribution of the soil changes and fine particles are lost; the dry density of the soil increases and the void ratio decreases. The internal friction angle φ of the soil and the cohesion force c increase with the consolidation, and the shear strength of the soil also increases. The source of debrisflows is reduced and the difficulty of starting is increased. From the curve of soil strength recovery, the active period of debris flow after the earthquake is about 15-25 years. In order to verify this law, this paper further studied the attenuation law of denuded data in the Longxi-Baisha river basin in the earthquake area after the Wenchuan earthquake, and from another point of view, the active period of debris flow after the earthquake was 26 years. Therefore, it is recommended that the calculation of the debris flow in the extreme earthquake area within 25 years after the earthquake should adopt the statistical formula method, and the matching method should be adopted after 25 years.Finally, in order to verify the applicability of the statistical formula method, the calculation of peak debris flows and the numerical simulation of the danger zone with different frequencies were performed using the statistical formula method and the matching method, respectively, for the Zier Gully in Kangding of the earthquake with high incidence. The results show that at the same frequency, the peak discharge of debris flow obtained by the statistical formula method is much larger than that of the matching method; the peak discharge of the statistical formula method once of 5 years return is similar to the calculation result of the matching method of 100 years return. For the important towns and important projects with strong tectonic movements, the statistical construction method is recommended for the construction of debris flow and disaster prevention and mitigation. |
Pages | 148 |
Language | 中文 |
Document Type | 学位论文 |
Identifier | http://ir.imde.ac.cn/handle/131551/24781 |
Collection | 山地灾害与地表过程重点实验室 |
Affiliation | 中国科学院成都山地灾害与环境研究所 |
First Author Affilication | 中国科学院水利部成都山地灾害与环境研究所 |
Recommended Citation GB/T 7714 | 高延超. 沟谷型泥石流规模频率关系及其在城镇危险区评价中的应用[D]. 北京. 中国科学院大学,2018. |
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