滑坡堰塞坝坝体溃决机理与溃决实验研究综述

相对于人工土石坝,天然形成的滑坡堰塞坝缺少加固、防渗及泄洪等工程措施来稳定堰塞湖水位,坝体结构不稳定、基础资料缺乏,发生的溃决现象具有突发性强、几率高、危险性大、排险处理紧迫的特点,亟需深入系统的研究.作者结合国内外堰塞坝形成及其溃决问题的研究现状,介绍了滑坡堰塞坝与人工土石坝的溃决特性、滑坡堰塞坝的溃决模式及寿命特征,以及滑坡堰塞坝溃决特性的物理模型试验研究、原型观测及大比尺现场试验研究、梯级滑坡堰塞坝溃决特性试验研究进展.最后提出了关于堰塞坝溃决机理、堰塞湖处置、溃决模式、原型及模型试验比尺效应、溃决过程原型监测预警等方面建议的研究方向.

Effects of river flow velocity on the formation of landslide dams

Natural dams are formed when landslides are triggered by heavy rainfall during extreme weather events in the mountainous areas of Taiwan.During landslide debris movement,two processes occur simultaneously:the movement of landslide debris from a slope onto the riverbed and the erosion of the debris under the action of high-velocity river flow.When the rate of landslide deposition in a river channel is higher than the rate of landslide debris erosion by the river flow,the landslide forms a natural dam by blocking the river channel.In this study,the effects of the rates of river flow erosion and landslide deposition(termed the erosive capacity and depositional capacity,respectively)on the formation of natural dams are quantified using a physics-based approach and are tested using a scaled physical model.We define a dimensionless velocity index vde as the ratio between the depositional capacity of landslide debris(vd)and the erosive capacity of water flow(ve).The experimental test results show that a landslide dam forms when landslide debris moves at high velocity into a river channel where the river-flow velocity is low,that is,the dimensionless velocity index vde>54.Landslide debris will not have sufficient depositional capacity to block stream flow when the dimensionless velocity index vde<47.The depositional capacity of a landslide can be determined from the slope angle and the friction of the sliding surface,while the erosive capacity of a dam can be determined using river flow velocity and rainfall conditions.The methodology described in this paper was applied to seven landslide dams that formed in Taiwan on 8 August 2009 during Typhoon Morakot,the Tangjiashan landslide dam case,and the Yingxiu-Wolong highway K24 landslide case.The dimensionless velocity index presented in this paper can be used before a rainstorm event occurs to determine if the formation of a landslide dam is possible.

Debris flow susceptibility analysis based on the combined impacts of antecedent earthquakes and droughts： a case study for cascade hydropower stations in the upper Yangtze River, China

The upper Yangtze River region is one of the most frequent debris flow areas in China. The study area contains a cascade of six large hydropower stations located along the river with total capacity of more than 70 million kilowatts. The purpose of the study was to determine potential and dynamic differences in debris flow susceptibility and intensity with regard to seasonal monsoon events. We analyzed this region's debris flow history by examining the effective peak acceleration of antecedent earthquakes,the impacts of antecedent droughts, the combined effects of earthquakes and droughts, with regard to topography, precipitation, and loose solid material conditions. Based on these factors, we developed a debris flow susceptibility map. Results indicate that the entire debris flow susceptibility area is 167,500 km^2, of which 26,800 km^2 falls within the high susceptibility area, with 60,900 km^2 in medium and 79,800 km^2 are in low susceptibility areas. Three of the six large hydropower stations are located within the areas with high risk of debris flows. The synthetic zonation map of debris flow susceptibility for the study area corresponds with both the investigation data and actual distribution of debris flows. The results of debris flow susceptibility provide base-line data for mitigating, assessing, controlling and monitoring of debris flows hazards.

Reflection of Typhoon Morakot-The Challenge of Compound Disaster Simulation

Climate change has altered locally singletype disasters to large-scale compound disasters because of increasing intensity and frequency of extreme rainfall events.The compound disasters can combine small-scale floods,debris flows,shallow landslides,deep-seated landslides,and landslide lakes into a large-scale single disaster event.Although simulation models and evaluation tools are available for single-type disasters,no single model is well developed for compound disasters due to the difficulty of handling the interrelationship between two successive single-type disasters.This study proposes a structure for linking available single-type simulation models to evaluate compound disasters and provides a useful tool of decision making for warning and planning of disaster reduction.

参加医学大学生创新性训练项目的实践与体会

"大学生创新性训练项目"是高等院校本科科研教学的重要组成部分,旨在打破传统的教育方法,创建以"学生主动发现问题、协商解决问题"为核心的教育模式,充分调动学生的主观能动性,激发其创新意识和团队合作精神,从而全面提升其创新能力与实践能力,为今后的科研之路打下基础。本文根据作者所参加的一项医学校级大学生创新性训练项目——乳酸菌对高脂SD大鼠胆固醇代谢的影响,在总体概括该项目情况的基础上,浅谈了参加大学生创新性训练项目的实践与体会。

收入不平等、需求有限性与经济增长效应研究——基于30个国家面板数据的分析

本文从收入不平等的角度探寻需求不足的成因和内在影响机制,研究发现总体有效需求水平在收入不平等对经济增长的影响中起到中介效应的作用。采用理论模型中的家庭收入结构性参数值表示收入不平等程度,这区别于传统使用基尼系数方法来测度收入差距水平。基于2000-2019年30个国家面板数据,模拟出家庭收入结构性参数并设定为核心解释变量,对家庭收入结构性参数、总体有效需求水平与人均GDP增长率的影响关系进行了相关分析。结果发现:家庭收入结构性参数的增大将引致总体有效需求水平的下降进而限制经济可持续增长,家庭收入结构性参数与人均GDP增长率呈现出显著的负相关关系。收入不平等程度的持续扩大对总体有效需求的持续增长形成限制性约束,总体有效需求不足的形成进一步限制总体经济的持续增长。这方面的研究为理解当前国内外需求不足和后工业化阶段增长现象提供了一个新的视角。