震后都汶公路沿线泥石流沟堵江危险性评估

震后泥石流松散物质显著增多,临界雨量降低,导致泥石流暴发频率增加、规模增大,从而使震后灾区泥石流堵江事件频繁发生,给灾区带来严重的二次灾害。为了评价震后泥石流堵江概率大小,本文在野外考察基础上,获得研究区泥石流沟基础数据,并根据水文模型计算不同频率下的泥石流规模; 在此基础上利用泥石流堵江公式,获取研究区域泥石流堵江危险程度(数值),并结合研究区域已发生的泥石流堵江事件,界定了泥石流堵江公式的临界值,使之能够更加准确用来判定泥石流堵江概率,并对 5·12 地震极震区都汶公路沿线的7条泥石流在不同频率下的泥石流堵江概率进行评价。评价结果显示:牛眠沟和关山沟在暴发50a及其以上泥石流时,会发生堵江; 烧房沟、红椿沟和磨子沟在暴发10a及其以上泥石流时,会发生堵江事件; 洱沟和太平沟在暴发5a及其以上泥石流时便可能发生堵江; 上述泥石流沟一旦发生堵江,便会给映秀镇和都汶公路带来严重灾难。通过本文获取的堵江临界值可以作为判定泥石流堵江的参考标准,为泥石流防治、预报提供参考,同时可以为灾后重建和预防二次灾害提供科学借鉴。     

Effects of model parameters,topography, and scale on the mass movement processes of debris avalanches using the discrete element method

The mass movement process of a debris avalanche is a complex dynamic system and is influenced by topographic conditions, material composition, sliding-bed surface conditions and other factors. A discrete element method is used to simulate the mass movement process of debris avalanches and is validated by laboratory flume tests. Sensitivity analyses for the model parameters show that a low bond strength indicates that a small impact force can lead to slope failure. The friction coefficient has a little effect on the mass movement process. However, high particle stiffness and bond strength causes the sliding material to behave like a rigid block of rock; therefore low bond strength and particle stiffness are selected to simulate the laboratory flume tests. The velocity of the sliding material increases with the increasing slope of the flume. If the sliding material hits a barrier, the travel direction will change and energy dissipation will occur, resulting in the sudden decrease in velocity. With an increase in landslide volume, the model parameters particle stiffness and parallel bond strength should be increased to ensure the reasonableness of the simulated results. When the landslide volume is not large enough, the selection of those model parameters has no significant effect on the movement process. The proper selection of model parameters is very important for the reasonableness of the simulated results.     

门头沟山区泥石流发育特征与岩石类型的相关性分析

不同类型岩石的成分和结构存在较大差异,使岩石自身及其风化物具有不同的物理力学性质,从而导致泥石流在不同类型岩石中的发育情况不同。门头沟山区目前存在12条泥石流沟,主要分布在砂岩地层和第四系堆积物地区。通过对泥石流沟的发育数量.松散物厚度和储量,沟道相对高差和主沟纵坡等主要特征要素与岩石类型之间的关系.进行统计分析.认为岩石类型从物源量.沟道形态和人类工程活动3个方面.影响着泥石流沟的发育。     

Initiation process of debris flows on different slopes due to surface flow and trigger-specific strategies for mitigating post-earthquake in old Beichuan County, China

The 12 May 2008 Wenchuan earthquake (Ms 8.0) in China, produced an estimated volume of 28 × 10⁸ m³ loosened material, which led to debris flows after the earthquake. Debris flows are the dominant mountain hazards, and serious threat to lives, properties, buildings, traffic, and post-earthquake reconstruction in the earthquake-hit areas. It is very important to understand the debris flow initiation processes and characteristics, for designing debris flow mitigation. The main objective of this article is to examine the different debris flow initiation processes in order to identify suitable mitigation strategies. Three types of debris flow initiation processes were identified (designated as Types A, B, and C) by field survey and experiments. In “A” type initiation, the debris flow forms as a result of dam failure in the process of rill erosion, slope failure, landslide dam, or dam failure. This type of debris flow occurs at the slope of 10 ± 2°, with a high bulk density, and several surges following dam failure. “B” type initiation is the result of a gradual increase in headward down cutting, bank and lateral erosion, and then large amount of loose material interfusion into water flow, which increases the bulk density, and forms the debris flow. This type of debris flow occurs mainly on slopes of 15 ± 3° without surges. “C” type debris flow results from slope failures by surface flow, infiltration, loose material crack, slope failure, and fluidization. This type of debris flow occurs mainly on slopes of 21 ± 4°, and has several surges of debris flow following slope failure, and a high bulk density. To minimize the hazards from debris flows in areas affected by the Wenchuan earthquake, the erosion control measures, such as the construction of grid dams, slope failure control measures, the construction of storage sediment dams, and the drainage measures, such as construction of drainage ditches are proposed. Based on our results, it is recommend that the control measures should be chosen based on the debris flow initiation type, which affects the peak discharge, bulk density and the discharge process. The mitigation strategies discussed in this paper are based on experimental simulations of the debris flows in the Weijia, Huashiban, and Xijia gullies of old Beichuan city. The results are useful for post-disaster reconstruction and recovery, as well as for preventing similar geohazards in the future.     

四川汉源康家坡滑坡形成机理与滑坡—堰塞坝—泥石流灾害链分析

2018年8月6日中午12时,汉源县富泉镇西沟发生大规模滑坡,约1.50×10~6 m~3松散碎块石土在前期持续降雨作用下沿西沟右岸高速滑出、解体,并在主沟道内形成堰塞坝,体积约4.00×10~5 m~3。滑坡造成1人失踪,近6.70×10~3 m~2耕地被毁,紧急转移50余人。通过现场实地调查,结合无人机航飞、三维建模、地质、地震、水文、气象等资料,对康家坡滑坡基本特征进行了调查研究,调查表明,有利的地形条件、松散的覆盖层、充沛的前期降雨入渗及溪水对坡脚的冲刷是形成滑坡的主要原因。西沟原本为一条高频泥石流沟,本文在此基础上分析了堰塞坝溃坝的可能性及灾害链成灾模式。     

三眼峪特大泥石流形成的物源条件分析

通过对舟曲县"8.8"特大山洪泥石流三眼峪沟进行现场调查,从泥石流的岩土体类型及特征、地质构造、水文地质、新构造运动及地震等方面,对物源条件的地质环境背景进行了总结.调查结果表明:①三眼峪沟泥石流的松散固体物质主要包括崩塌堆积物、滑坡堆积物、残坡积物和冲洪积物.②三眼峪沟松散固体物质总量4079.42×104m3,流域...     

帕隆藏布江特大型泥石流的成灾模式及防治对策——以扎木镇-古乡段为例

文章通过对雅鲁藏布江的Ⅰ级支流—帕隆藏布江扎木镇-古乡段辫状水系地貌的研究,认为其与两岸支谷发育的泥石流群有关。通过对位于该河段下游的古乡沟和上游的地质弄巴泥石流特征的重点剖析,发现了特大型泥石流发育的2个重要特征,即支谷上游冰蚀围谷中赋存大量巨厚古今冰碛物和支谷中游峡谷段大型崩塌滑坡坝溃决。提出了特大型泥石流的成灾模式,并以该成灾模式解释了2000年易贡巨型滑坡堵江事件。最后,提出了基于上述成灾模式的帕隆藏布江流域特大型泥石流灾害防治的原则和方法。     

甘肃河西地区泥石流沟分布特征与易发性评估研究

根据汇水面积、松散物质储量、沟坡坡度、主沟纵坡降等4项泥石流沟易发性判断特征指标,利用数理统计方法,对甘肃省河西地区20个县、区、市的587条泥石流沟现状进行了分析研究. 结果表明：河西地区泥石流多发育在南北山地的前山走廊地带,泥石流沟分布密度稀疏,属于泥石流稀疏地区. 在泥石流沟易发性主要特征指标方面,研究区汇水面积指标处于偏轻微程度,松散物质储量指标处于中等程度,沟坡坡度指标处于严重程度,主沟纵坡降指标处于中等以下程度. 在泥石流沟易发性评价结果方面区域总体属于泥石流地质灾害低易发-中易发区域. 在全球气候变暖的背景下,研究区内强降水情况发生频率呈现增强趋势,应积极开展极端天气影响下河西地区泥石流发展趋势和干旱、半干旱地区植被特征与泥石流易发性之间的相关关系研究.     

Catastrophic debris flows triggered by a 4 July 2013 rainfall in Shimian,SW China: formation mechanism,disaster characteristics and the lessons learned

On 4 July 2013, three catastrophic debris flows occurred in the Hougou, Majingzi, and Xiongjia gullies in Shimian county and produced debris dams and river blockages, resulting in serious casualties and huge economic loss. Though debris flows have been identified prior to the catastrophic events, their magnitudes and destructive power were far beyond early recognition and hazard assessment. Our primary objective for this study was to explore the formation mechanism and typical characteristics and to summarize the lessons learned from these disastrous events in order to avoid the repeat of such disasters in the future. Based on field investigation and imagery interpretation of remote sensing carried out following the catastrophic events, four conclusions were drawn: (1) The catastrophic debris flows were initiated from surface-water runoff, and the triggering factor was attributed to the local intensive rainfall with an hourly intensity of more than 46.7 mm. (2) Entrainment was the most important sediment-supplying method for the debris flow occurrence, and the source materials transported by debris flows from the three gullies were estimated to be about 97?×?10⁴ m³ in volume altogether. (3) As surface-water runoff eroded and entrained hillslope and channel materials persistently, debris flows were characterized by intensive incision at upper or middle reaches and significant magnification effect in flow discharge and volume downstream. Corresponding peak discharge surveyed at the outlets of the Hougou, Majingzi, and Xiongjia gullies was estimated up to 751.0 m³/s, 870.1 m³/s, and 758.7 m³/s, respectively. (4) Debris flows that occurred from the three gullies all belonged to viscous ones and the bulk densities were calculated more than 1.80 g/cm³, indicating a huge carrying capacity and destructive impacting power. In addition, the lessons learned from the catastrophic events were summarized, including recognition and assessment on debris flow hazard and utilization of deposition fan. In this paper, prevention suggestions on debris flow prone valleys with high-vegetation coverage and low occurrence frequency were also put forward. The results of this study contribute to a better understanding on the initiation mechanism, dynamic characteristics, and disaster mitigation of debris flows initiated from intense rainfall and surface-water runoff in mountainous areas.     

低山丘陵区典型滑坡-泥石流链生灾害特征与成灾机理

2019年6月10—13日,龙川县发生持续强降雨,导致全县境内发生大量滑坡、泥石流灾害,贝岭镇米贝村是三个重灾区之一。本文以贝岭镇米贝村6号沟发生的滑坡-泥石流链生灾害为研究对象,在野外精细化调查测量基础上,结合数值模拟分析与计算,对链生灾害特征与成灾机理展开研究。研究发现:①6号沟内共发育7处浅层土质小型滑坡,仅3号滑坡体与部分6号滑坡体转化为泥石流,构成泥石流主要物源,其余滑坡未构成持续性影响;②持续降雨下渗,坡体由非饱和向饱和状态转变,坡表形成连续饱和区,孔隙水压力的增加与孔隙水的软化促使土体强度降低,加之坡体饱和自重的增大,斜坡发生浅表层失稳破坏;③降雨的持续下渗与支沟沟源“漏斗状”地形下的地表汇水快速增大滑坡松散堆积体内的含水率,促使其物理性质发生变化,在重力势能下呈流态状启动、运动转化为泥石流。降雨结构影响滑坡-泥石流链生过程,前期降雨引发滑坡、后期降雨启动形成泥石流,滑坡与泥石流的发生表现出阶段性特征。研究成果有助于指导当地政府进一步开展滑坡-泥石流链生灾害的防灾减灾工作,也为该地区未来区域预警研究工作提供理论支撑。     

Susceptibility analysis of large-scale debris flows based on combination weighting and extension methods

Susceptibility is an important issue in debris flow analysis. In this paper, 26 large-scale debris flow catchments located in the Wudongde Dam site were investigated. Seven major factors, namely, loose material volume per square kilometer, loose material supply length ratio, average gradient of the main channel, average hill slope, drainage density, curvature of the main channel, and poor vegetation area ratio, were selected for debris flow susceptibility analysis. Geographic information system, global positioning system, and remote sensing, collectively known as 3S technologies, were used to determine major factors. Weights of major factors affecting debris flow susceptibility were determined. This paper applied the combination weighting method, which considers both the preference of the engineers for major factors and the objective major factor information by using analytic hierarchy process and entropy method. Combination weights of major factors for the investigated 26 debris flow catchments are 0.20, 0.12, 0.20, 0.10, 0.08, 0.19, and 0.11, respectively. Combination weights follow the order of loose material volume per square kilometer = average gradient of the main channel > curvature of the main channel > loose material supply length ratio > poor vegetation area ratio > average hill slope > drainage density. This paper applied extension theory, which is used to solve incompatibility and contradiction problems, to determine susceptibility. Susceptibility results show that the susceptibility of 4 debris flow catchments are very low, 13 are low, 8 are moderate, and 1 is high. Assessment results exhibit consistency with the activity analysis.     

汶川震区典型泥石流动态演变特征研究——以绵竹市走马岭泥石流为例

汶川地震后,流域内产生大量松散物源,使走马岭沟由一季节性冲沟演变为一条潜在泥石流沟,在地震后的3个汛期内发生多次泥石流,并造成灾害,其中以2008-9-24泥石流和2010-8-13泥石流最为严重。本文利用3期遥感影像并结合野外调查,对走马岭沟泥石流的形成条件进行了论述,对比分析了走马岭泥石流沟2008年、2009年、2010年3个汛期后流域的动态变化特征,主要表现为:(1)在不同降雨强度下,走马岭泥石流具有复合型物源区启动方式,并先从局部性支沟发生泥石流,进而演变为整个流域全面暴发泥石流。(2)经历了2008年、2009年、2010年3个雨季后,走马岭流域物源储量及物源供给形式发生变化,其中崩塌规模增加了1.87%; 滑坡增加了25.35%; 沟道及坡面松散堆积减少了67.47%,减少部分大部分转化为泥石流沟道堆积物。(3)不同降雨强度下,走马岭泥石流堆积区范围边界变化明显,且不同堆积扇间存在叠加关系; 结合走马岭"9·24"堆积扇范围和"8·13"堆积扇前缘堆积痕迹及影像特征,推测出走马岭"8·13"堆积扇堆积面积约8.76×104m2。最后对泥石流成因机理及发展趋势进行了初步分析。结果显示,走马岭为一高频泥石流沟,仍具备形成大规模泥石流的条件。     

安宁河流域典型沟谷泥石流危险性评价

冕宁县安宁河流域为地质灾害密集分布区,安宁河断裂穿越于此,构造复杂,冷渍沟在上游左岸发育。在强降雨条件下,该沟就会暴发泥石流,堵塞安宁河流域和掩埋杀叶马村房屋和道路。冷渍沟泥石流具有流域面积小,主沟长度短,沟床纵比降大等特征,为了研究安宁河流域内泥石流的危险性,以冷渍沟为例,分析不同降雨周期下的泥石流暴发强度,模拟泥石流的运动过程并进行危险性评价。模拟的最大流速、最大堆积深度和降雨强度三者结合建立冷渍沟泥石流危险性评价模型。研究结果表明,冷渍沟泥石流危险范围内高危险区域占27%,主要集中在松散固体物质较多的沟道,中危险性区域和低危险区域各占56%和17%,该结论为危险范围内的居民和重点设施的风险管控提供参考。     

四川西昌“3·30”火烧区响水沟火后泥石流成灾机理

2020年3月30日,西昌市经久乡发生森林大火,响水沟流域植被被林火大面积烧毁,同年雨季,响水沟流域内多条沟道暴发泥石流,其中1#、2#、3#沟毗邻居民房屋和耕地,影响较为严重。通过野外调查、遥感解译和室外试验,以响水沟1#、2#、3#沟为研究对象,分析了不同林火烈度下,渗透特征、坡面侵蚀和沟道侵蚀的差异,从而揭示响水沟火后泥石流的成灾机理。结果表明,林火是泥石流暴发的重要诱因,火后泥石流的降雨阈值会明显降低。林火干扰导致坡面土壤的渗透系数表现出不同程度的降低,林火烈度越严重的区域,渗透系数越小,降雨更大比例地转化为坡面径流参与到坡面侵蚀。随降雨次数的增多,轻度、中度、重度火烧区域的坡面土壤侵蚀深度均增加;中度、重度林火烈度的侵蚀深度差异不大,且明显高于轻度区域,说明当林火烈度达到中度时,坡面土壤便会受到较大程度的侵蚀。地形条件相似的沟道,林火烈度越严重,泥石流侵蚀能力越强,最终体现于沟道两岸崩滑体数量越多,沟道宽度和深度越大。     

强震区高位滑坡远程灾害特征研究——以四川茂县新磨滑坡为例

近年来,在汶川地震等强震区常发生一种特大的高位滑坡地质灾害,它从高陡斜坡上部位置剪出并形成凌空加速坠落,具有撞击粉碎效应和动力侵蚀效应,导致滑体解体碎化,从而转化为高速远程碎屑流滑动或泥石流流动,并铲刮下部岩土体,使体积明显增加。新磨滑坡就是这种典型,它发生于2017年6月24日,滑坡后缘高程约3450m,前缘高程约2250 m,高差1200 m,水平距离2800 m,堆积体体积达1637×10~4m~3,摧毁了新磨村村庄,导致83人死亡。新磨滑坡地处叠溪较场弧形构造带前弧西翼,母岩为中三叠统中厚层变砂岩夹板岩,是1933年叠溪Ms7.5级震中区(烈度X度)和汶川Ms8.0级强震区(烈度IX度),形成震裂山体。滑源区分布多组不连续结构面,将厚层块状岩体分割成碎裂块体,在高程3150~3450 m区间形成明显的压裂鼓胀区,特别是存在2组反倾节理带,具有典型的"锁固段"失稳机理。滑坡体高位剪出滑动,连续加载并堆积于斜坡体上部,体积达390×10~4m~3,导致残坡积岩土层失稳并转化为管道型碎屑流;碎屑流高速流滑至斜坡下部老滑坡堆积体后,因前方地形开阔、坡度变缓,转化为扩散型碎屑流散落堆积,具有"高速远程"成灾模式。据此,可建立强震山区高位滑坡的早期识别方法,当陡倾山脊存在大型岩质高位滑坡时,应当考虑冲击作用带来的动力侵蚀效应和堆积加载效应,特别是沿沟谷赋存丰富的地下水时,发生高速远程滑坡的可能性将明显增加。因此,在地质灾害调查排查中,在高位岩质滑坡剪出口下方的斜坡堆积体上的聚居区等应划定为地质灾害危险区。在强震山区地质灾害研究中,不仅应采用静力学理论分析滑坡的失稳机理,而且应采用动力学方法加强运动过程的成灾模式研究。     

岷江上游大白杨沟泥石流特征及成因

大白杨沟流域位于岷江上游四川省茂县境内,处于叠溪镇较场山字型构造北端。该沟曾于1935年和1991年暴发过两次较大规模泥石流灾害,其中1935年暴发的泥石流受1933年叠溪7.5级地震影响,规模很大,其泥石流峰值流量达到557 m3/s。通过对大白杨沟流域两条支沟(小沟、大沟)的地形条件、水源条件及物源条件的特征分析,得出两条支沟具有形成泥石流的充分条件:(1)大沟沟道平均纵比降275‰,小沟为398‰,相对高差达2 023 m;(2)大沟拥有的物源总量为29.21万m3,小沟达到42.01万m3,物源丰富。这些条件很好地解释了小沟泥石流的强活动性。对后期泥石流的形成机制进行分析,大沟以"消防水管效应"形成泥石流为主,小沟则以"消防水管效应"和堰塞体溃决两种方式形成泥石流。最后,通过泥痕法还原了历史泥石流流量,并对后期泥石流流量做了较合理的预测,为大白杨沟泥石流灾害防治提供可靠的数据。     

九寨沟震区“6·21”泥石流成因与致灾机制研究

2019年6月20日晚九寨沟普降大到暴雨,导致九寨沟景区内卓追沟、下季节海子沟、则查洼沟等多处发生泥石流。3条泥石流沟分别冲出固体物质2.79×104m3、3.7×104m3,2.67×104m3,造成多处停淤挡墙及拦砂坝损坏,并淤埋了景区内的部分道路,造成了交通的短时间中断。根据灾后地面调查和遥感解译,初步查明了本次泥石流灾害的成因和致灾过程机制。灾害成因:地震引发的崩塌滑坡产生大量的新增松散固体物源与原有的沟坡堆积物(包括老泥石流堆积物)在强降水的作用下形成泥石流,因此本次泥石流是地震和降雨共同作用的结果。通过泥石流发生前后各流域沟道纵剖面和典型横断面调查分析,发现泥石流致灾过程机制主要包括:(1)泥石流冲刷沟道使老泥石流堆积物参与泥石流运动、同时诱发沟岸失稳崩塌,因而增强泥石流规模和冲击力等动力学参数;(2)沟道卡口和崩滑体滑入沟道后导致泥石流堵塞,在后续泥石流的作用下发生级联溃决,进而增大泥石流峰值流量和冲击力等动力学参数。在两种机制的共同作用下,泥石流规模和冲击力等参数可能超出防治工程规划设计指标,进而导致防治工程损毁并淤埋道路。因此,建议充分考虑地震与强降雨复合作用下九寨沟景区泥石流风险评估、防治工程规划设计的合理性和可靠性等关键问题,以保障景区安全。     

Effects of fine particle content and sample scale on the failure properties of loose landslide deposits

A large amount of loose landslide deposits caused by a strong earthquake can cause several mountain disasters (slope failures, debris flows, and others) under heavy rainfall conditions. Loose landslide deposits are sensitive to water due to their special structural properties, such as loose structure and wide grading. There are complex conformational and mechanical responses of loose deposits, but the initial conditions and formation mechanisms of mountain disasters can be described by several different parameters. Among these parameters, the property of failure is one of the most important, and it is used to describe extremely dangerous situations for each kind of disaster. In this study, a two-dimensional particle flow code platform (PFC2D) was used to simulate the failure properties, and a laboratory test verified the validity of the numerical experiments. Different sample scales (S1, 150?×?300 mm; S2, 300?×?600 mm; S3, 600?×?1200 mm) and fine particle contents smaller than 5 mm (f-1, 20%; f-2, 30%; f-3, 40%) were considered. The simulation results show that failure stress increases with increasing sample scale or fine particle content under low confining pressure and decreases under high confining pressure. The tendency of failure stresses to vary mutates with different fine particle contents when the confining pressure changes. The mutation value of the confining pressure is 280 kPa. In addition, the phenomenon of strain softening becomes less obvious when the confining pressure increases.     

人工降雨条件下冲沟型泥石流起动试验研究

下垫面以位于贡嘎山东坡的熊家沟为模型,开展了不同降雨强度条件下冲沟型泥石流起动的模拟试验,初步研究了冲沟型泥石流的形成机理和演化特征.试验研究表明:(1)在强降雨条件下,水体入渗速度、不同深度土体含水量变化与降雨强度呈反比例关系,降雨强度越大,越不利于水体入渗,而有利于坡面汇流、冲沟径流和下切侵蚀; (2)在强降雨和径流条件下,土体破坏方式、破坏程度以及泥石流形成机理表现出差异性.相对较小雨强降雨条件下,土体破坏方式以滑坡为主,泥石流形成模式表现为滑坡液化与转化起动,雨强较大降雨条件下,土体破坏方式以侵蚀垮塌为主,泥石流形成模式为洪流席卷垮塌体和沟床揭底; (3)起动试验中泥石流阵性特征明显.在强降雨条件下,雨强与泥石流的规模、黏度之间没有正相关性,雨强越大,泥石流黏度越小,试验中多出现的是高含砂洪流,而相对较小雨强作用下由土体液化转化形成的泥石流黏度较大.试验现象和结果与熊家沟泥石流起动、发生过程具有较高的一致性.     

城市泥石流沟的治理启示——以深沟为例

为研究典型工程措施在泥石流沟治理中的作用及影响,结合野外调查及历史资料,对云南东川城区的深沟泥石流治理进行总结：深沟在一系列坝系群建设和多年植树造林的治理下,发育了一定规模的阶梯一深潭系统,使沟道阻力明显增强（经测河床结构强度5p达0．3以上）,消减了泥石流能量,并保护河床不被侵蚀下切,岸坡稳定;而另一方面林草生长能提...