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沟谷型泥石流沿程冲淤特征及影响因子研究——以云南蒋家沟为例
Alternative TitleResearch on Scouring and Deposition Features and Impact Factors of Gully Debris Flow——A Case Study on Jiangjia Gully, Yunnan Province
Language中文
常士秋
Thesis Advisor王道杰
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name硕士
Degree Discipline自然地理学
Keyword沟槽形态 蒋家沟 沟谷型 冲淤特征 弯道系数
Other Abstract

泥石流冲淤现象普遍存在于泥石流运动过程之中,在沟谷型泥石流的流通区,冲淤特征在不同位置呈现出差异性,引起差异性的影响因子也不尽相同。本文以蒋家沟2003年以来的沟谷断面测量资料为基础,计算各断面历次测量间断面的平均冲淤深度,对比沟谷不同位置的断面间以及同一断面在不同测量时间下的冲淤差异,得到蒋家沟在近年来断面变化的时空分异规律。此外,将断面观测资料与泥石流运动参数资料相结合,利用线性拟合的方法分析了泥石流规模、沟床比降、输沙沟槽弯曲系数与泥石流冲淤深度之间的关系。并设计试验模拟不同形态的输沙沟槽,重点探讨输沙沟槽形态对泥石流淤积过程的影响,分析单场次泥石流淤积的空间分异。在蒋家沟雨季新发泥石流所形成的淤积区域内设置取样断面进行取样分析,得到泥石流淤积物级配在水平方向和垂直方向上的变异规律。主要结论如下:(1)2003年以来蒋家沟断面整体以淤积为主,不同位置断面的冲淤空间分异明显。从上游至下游,断面平均淤深呈减小趋势,最下游的3个断面呈现冲刷为主的演变特征。2010年以来蒋家沟平均淤深最大断面由先前的D7向其上游D1断面转移,表明近年来受蒋家沟泥石流活动逐渐减弱,受泥石流影响的区域在逐渐缩小。(2)野外观测资料分析表明,泥石流规模与泥石流淤积存在正相关关系,规模越大,淤积量就越大;沟床比降泥石流淤积存在负相关关系,沟床比降越大,平均淤积深度越浅;输沙沟槽弯曲系数与泥石流淤积存在正相关关系。(3)模拟实验结果显示,与无沟槽地形相比,直道输沙沟槽的存在可加强泥石流的下泄能力。相同横断面面积条件下的输沙沟槽,不同宽深比引起的水力半径差异是影响泥石流下泄能力的主要因素。(4)模拟实验结果显示,泥石流堆积物横断面面积变化趋势随泥石流流距的增大呈近似开口朝下的抛物线,堆积物横断面面积的峰值与抛物线对称轴临近。横断面面积的峰值位于泥石流最初出现淤积位置不远处的下游地区,在峰值的两侧,面积变化随流距的增加是先增大后减小的规律。经对比还发现,沟道越大,初始泥石流量越多,在流距上对应的淤积峰值就会相对的往后推移。同样的,弯道系数的存在,也影响了淤积峰值的位置。(5)实验结果还分析了堆积物体积与流距的关系,体积变化趋势与横断面面积随流距的变化规律基本一致,但是体积变化与流距的拟合关系更加密切,这为我们更准确地研究泥石流冲淤规律提供了参考,利于分析。(6)泥石流淤积区取样分析结果显示,上层堆积物的中值粒径小于下层堆积物的中值粒径;在横向上,泥石流堆积物边缘位置相较于中间位置孔隙度小、分选好;泥石流堆积物中值粒径和孔隙度随泥石流流距的增加而减小。

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Scouring and deposition is common phenomenon in debris flow, especially in flowing area of debris flow, the characteristic of scouring and deposition in different position is divers, so does its reason. Based on cross-section measurement data of Jiangjia Ravine from 2003, the average depth of scouring and deposition of all measurement is calculated. In addition, comparing deposition depth of cross-sections in different location and one cross-section in different measurement time in the ravine, spatial and temporal variation of Jiangjia Ravine is obtained. Combine cross-section measurement data and observation data of debris flow, the relationship between disposition depth and discharge of debris flow, groove gradient and meander ratio of sediment groove is analyzed by linear fit. Design test equipment to simulate different forms of sediment groove to further investigate the impact of groove forms to sediment deposition process and debris flow deposition spatial differentiation in single event. Set cross-section within the deposition region in Jiangjia Ravine rainy season to sample and analyze, debris flow deposition law in the horizontal and vertical variation law is obtain. The main conclusions are as follows:(1) Siltation is the main change law in Jiangjia Ravine Since 2003, the change among different cross-sections is clear. From upstream to downstream, the average silt depth of deposition tends to a decreasing trend, the most downstream 3 sections present erosion in most time. Since 2010, the maximum of average silt deep located in Jiangjia Ravine transferred from the previous section D7 to its upstream section D1, show that debris flow activity weakened gradually in recent years, the area affected by debris flow was narrowing gradually.(2) As the field observations data analysis showed, runoff volume of the debris flow and debris flow deposition presented linear positive correlation, the deposition deep increased with the increase of runoff volume. The bigger the groove bed is, the deeper the deposition. There is a positive correlation between gully bed slope and debris flow deposition, the bigger the slope, the shallower the deposition. The relationship between meander ratio of sediment groove and deposition is linear positive correlation. (3) Simulation results show that compared with no groove terrain, the presence of sediment trench enhance debris flow discharged capacity. Under the same cross-sectional area of the sediment groove conditions, hydraulic radius caused by different width to depth ratio is the main factor affecting the ability of the debris flow discharged.(4) Simulation results show that the variation tendency of cross-sectional area was similar to downward opening parabola shape, the peak value of cross-sectional area neared the parabola symmetry axis; the peak value of cross-sectional area came in the flow distance about 0.5m to 1m, on the both side of the peak value, the cross-sectional area tended to decrease after the first increase. Comparison also found that the greater the hydraulic radius, the more the initial amount of debris flow, the peak value of cross-sectional area came more farer. Similarly, hydraulic radius also affected the location of the peak value of cross-sectional area.(5) This study also analyzed the relationship between the volume of deposits with the flow distance, the trend law of volume variant is similar to cross-sectional area variation, but the fitting relationship between volume change and flow distance is more accurate, which provides a good reference for us to study debris flow erosion law. (6) Debris flow deposition zone sampling analysis showed that the median diameter of the upper layer was less than the median diameter of the lower deposits; in the transverse direction, compared to the intermediate position, edge position had small porosity and well sorted; stream farther away debris had a median particle size is smaller, the smaller the porosity, the better sorting; debris had a bigger median particle size and porosity decreases with increased distance of debris flow stream. 

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18860
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
Recommended Citation
GB/T 7714
常士秋. 沟谷型泥石流沿程冲淤特征及影响因子研究——以云南蒋家沟为例[D]. 北京. 中国科学院大学,2016.
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