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强震区泥石流启动机制 总被引：2，自引：0，他引：2
地震区的泥石流物源主要来源于滑坡、崩塌等松散体,具有结构疏松,密实度低,堆积时间短等特点,与非地震环境中的滑坡、崩塌堆积体的结构有所不同,堆积体的物理力学性质发生了改变,堆积体转换为泥石流所需的外界条件也相应的改变。以汶川地震区都江堰市龙池镇典型泥石流灾害为例,分析了地震滑坡、崩塌松散体的堆积形态和堆积体的应力环境。从静力学和动力学角度分析堆积体在强降雨条件下的起动特征,探讨了降雨作用形成的地表径流水深与堆积体失稳时的应力极限状态的关系。分析得出沟道岸坡滑坡堆积体发生侵蚀时的地表径流力为F=(τ1f-f1sinα)/cos(α-26.65),并建立径流水深与地表径流力的关系:H=F/4ρsgJ。分析在动量守恒条件下,堆积体单位时间内的侵蚀体积dV=dM/γs模型。为了进一步探讨在实际现场的应用,以汶川地震区都江堰市的水打沟泥石流为例,分析发生泥石流时的地表径流水深为0.011 m,其结论与实际调查结果基本一致。 相似文献
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泥石流沟道汇流对堆积危险范围影响的数值模拟研究 总被引：1，自引：0，他引：1
利用离散元法和图形处理器（GPU）并行计算手段建立泥石流运动堆积模型,以自然界沟道泥石流汇流后运动堆积特征及危险范围作为模拟参照,利用所构建的泥石流流通槽完成沟道泥石流不同交汇角汇流模拟试验和堆积危险范围预测,实现了泥石流沟道汇流的可视化模拟和数值模拟。试验结果表明,可视化模拟能够模拟出自然界中泥石流自流通区运动汇流后产生堆积的运动特征;数值模拟实现了锐角条件下仅考虑单因素即沟道交汇角对泥石流堆积危险范围影响的模拟试验。此外,利用GPU并行计算的优势可用于模拟大规模泥石流汇流现象,模型的可扩展性为泥石流汇流堆积危险范围分析向更为复杂的地理环境模拟奠定基础。 相似文献
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浙江地处我国东南沿海,近几年频繁遭受泥石流等山地灾害的危害。由于所处地理地质和气候环境,发育的泥石流有其独特的地域特征。从泥石流的发育特征、形成过程等探讨了浙江泥石流形成的机理,分析了其成灾特点。结果表明,浙江省泥石流为滑坡、崩塌转化型泥石流,泥石流的形成机理及过程主要为:强降雨下滑坡、崩塌发生,持续强降雨使得滑坡、崩塌松散物流化从而形成泥石流。滑坡、崩塌转化型泥石流在流域特征上表现为形成区坡度大,易发滑坡、崩塌,水力条件充分等。泥石流灾害具有低频性、群发性、并发性、突发性、夜发性、危害大等特点。 相似文献
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In modelling complex a-centric phenomena which evolve through local interactions within a discrete time-space, cellular automata (CA) represent a valid alternative to standard solution methods based on differential equations. Flow-type phenomena (such as lava flows, pyroclastic flows, earth flows, and debris flows) can be viewed as a-centric dynamical systems, and they can therefore be properly investigated in CA terms.SCIDDICA S4a is the last release of a two-dimensional hexagonal CA model for simulating debris flows characterised by strong inertial effects. S4a has been obtained by progressively enriching an initial simplified model, originally derived for simulating very simple cases of slow-moving flow-type landslides.Using an empirical strategy, in S4a, the inertial character of the flowing mass is translated into CA terms by means of local rules. In particular, in the transition function of the model, the distribution of landslide debris among the cells is obtained through a double cycle of computation. In the first phase, the inertial character of the landslide debris is taken into account by considering indicators of momentum. In the second phase, any remaining debris in the central cell is distributed among the adjacent cells, according to the principle of maximum possible equilibrium.The complexities of the model and of the phenomena to be simulated suggested the need for an automated technique of evaluation for the determination of the best set of global parameters. Accordingly, the model is calibrated using a genetic algorithm and by considering the May 1998 Curti–Sarno (Southern Italy) debris flow.The boundaries of the area affected by the debris flow are simulated well with the model. Errors computed by comparing the simulations with the mapped areal extent of the actual landslide are smaller than those previously obtained without genetic algorithms. As the experiments have been realised in a sequential computing environment, they could be improved by adopting a parallel environment, which allows the performance of a great number of tests in reasonable times. 相似文献
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广东省地质灾害较为常见,崩塌、滑坡、泥石流是其中比较严重的3种类型。基于现有的泥石流危险度评价原理和方法,建立了可用于广东省崩塌、滑坡、泥石流灾害危险性的评价模型。以全省88个县级评价单元为基础,根据崩塌、滑坡、泥石流灾害危险度评价结果,将广东省共分为3个危险等级区,其中高度危险区8个县,占总数的9.1%;中度危险区60个县,占总数的68.2%;低度危险区20个县,占总数的22.7%,据此制成广东省崩塌、滑坡、泥石流灾害危险等级图。高度危险区主要位于粤北山区,危险度数值介于0.6～0.72之间;中度危险区连片分布,是全省崩塌、滑坡、泥石流灾害的主体部分,危险度数值介于0.4～0.6之间;低度危险区集中分布在平原区及低平台地区,危险度数值介于0.31～0.4之间。采用1994―2009年广东省防灾减灾年鉴和广东省地质灾害防治规划(2001―2015年)中的统计数据,验证了本文的研究成果与实际情况具有较高的一致性。 相似文献
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山地灾害研究的发展态势与任务 总被引：3，自引：0，他引：3
泥石流、滑坡等山地灾害已成为世界各国十分关注的自然灾害问题。据最近几年的国际学术会议,泥石流、滑坡研究的前沿领域是：泥石流、滑坡活动的地带性与全球气候变化的规律；泥石流、滑坡起动机理、动力学模型；泥石流、滑坡等山地灾害风险分析、发生时间预报；成灾机理与减灾防灾关键技术。国内研究较晚,但发展很快。经过近50 a的研究,涉及上述诸多研究颁域。但研究不深,还存在不少差距。据国内外研究态势,针对山地所实际,提出了在泥石流、滑坡理论创新和防治关键技术等研究方面12条任务。 相似文献
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In many mountainous areas, the rapid development of urbanisation and the limited space in the valley floors have created a need to construct buildings in zones potentially exposed to debris flow hazard. In these zones, a detailed and coherent hazard assessment is necessary to provide an adequate urban planning. This article presents a multidisciplinary procedure to evaluate the debris flow hazard at a local scale. Our four-step approach was successfully applied to five torrent catchments in the Principality of Andorra, located in the Pyrenees. The first step consisted of a comprehensive geomorphologic and geologic analysis providing an inventory map of the past debris flows, a magnitude–frequency relationship, and a geomorphologic–geologic map. These data were necessary to determine the potential initiation zones and volumes of future debris flows for each catchment. A susceptibility map and different scenarios were the principal outcome of the first step, as well as essential input data for the second step, the runout analysis. A one-dimensional numerical code was applied to analyse the scenarios previously defined. First, the critical channel sections in the fan area were evaluated, then the maximum runout of the debris flows on the fan was studied, and finally simplified intensity maps for each defined scenario were established. The third step of our hazard assessment was the hazard zonation and the compilation of all the results from the two previous steps in a final hazard map. The base of this hazard map was the hazard matrix, which combined the intensity of the debris flow with its probability of occurrence and determined a certain hazard degree. The fourth step referred to the hazard mitigation and included some recommendations for hazard reduction. In Andorra, this four-step approach is actually being applied to assess the debris flow hazard. The final hazard maps, at 1 : 2000 scale, provide an obligatory tool for local land use planning. Experience achieved during the study showed that the collaboration between geologists, geomorphologists, engineers, and decision makers is essential and that only a multidisciplinary approach allows for solving all the problems of such a complex process as debris flows. Finally, we propose that our approach may be applied to other mountainous areas, adapting the hazard matrix to new local conditions. 相似文献
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After the Wenchuan earthquake in China, debris flows have been more frequent. Multiple debris flows commonly occur in earthquake-affected areas during heavy rainfall, often causing losses of lives and property. We analyzed the dynamic movement of debris flows and proposed a quantitative method of debris flow hazard assessment, based on kinetic energy. Validated using field study of an actual debris flow disaster, these analyzes help determine the type, quantity, distribution, economic worth, and susceptibility of elements at risk. We established a method to determine vulnerability of elements at risk and we propose a systematic and quantitative method for local risk analysis of debris flows. We applied the proposed method to a debris flow in Qipan gully, which caused serious damages for Duwen Highway and Qipan settlements of Sichuan Province in 2013. With the support of a debris-flow movement numerical simulation, remote sensing, and GIS techniques, the proposed method analyzed disaster effects and divided the hazardous areas into three risk zones. Calculated risk zones coincided with the actual distribution and severity of damage of the event, suggesting that the risk assessment generated by the proposed method is consistent with results from the actual disaster. 相似文献
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委内瑞拉1999年特大泥石流灾害 总被引：10，自引：2，他引：8
受娜尼拉现象的影响,１９９９－１２－１５～１６委内拉北部阿维拉册区加勒比海沿岸的８个州连降特大暴雨,造成山体大面积滑塌,数十条沟谷同时暴发大规模的泥石流。泥石流造成３万人死亡、经济损失高达１００亿美元,成为本基纪最严重的泥石流灾害,这次泥石汉灾害具有群发性、规模大、低频率和直接入海等特点,对这类泥石流进行泥石流成因、活动规律、预测预报、泥石流与异常气候现象关系和直接入海型泥石流运动规律,沉积特征、 相似文献
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A dynamic model for rainfall-induced landslides on natural slopes 总被引：18，自引：0，他引：18
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A case study of coseismic landslides and post-seismic sedimentary impacts of landslides due to rainfall events was conducted in the Tachia River basin, Taichung County, central Taiwan. About 3000 coseismic landslides occurred in the basin during the ML 7.3 Chi-Chi earthquake in 1999. The deposits from these landslides provided material for numerous debris flows induced by subsequent rainfall events. The estimated 4.1 × 107 m3 of landslide debris produced in the upland area caused sediment deposition in riverbeds, and flash floods inundated downstream areas with sediment during torrential rains. The landslide frequency-size distributions for the coseismic landslides and the subsequent rainfall-induced landslides were analyzed to determine the sediment budgets of the post-seismic geomorphic response in the landslide-dominated basin. Both the coseismic and the rainfall-induced landslides show a power–law frequency-size distribution with a rollover. It was found that the rainfall-induced landslide magnitude was smaller than the coseismic one, and that both have comparable negative scaling exponents in cumulative form, of about − 2.0 for larger landslides (> 10− 2 km2). This may be attributed to ongoing movement or reactivation of old landslides, and a natural stabilisation of small landslides between 10− 4 and 10− 2 km2. It is proposed that the characteristics of geological formations and rainfall as well as changes in landslide area are reflected in the power–law distribution. 相似文献
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Spatial patterns of old, deep-seated landslides: A case-study in the northern Ethiopian highlands 总被引：1，自引：0，他引：1
M. Van Den Eeckhaut J. Moeyersons J. Nyssen Amanuel Abraha J. Poesen Mitiku Haile J. Deckers 《Geomorphology》2009,105(3-4):239-252
During the last decade, slope failures were reported in a 500 km2 study area in the Geba–Werei catchment, northern Ethiopia, a region where landslides were not considered an important hazard before. Field observations, however, revealed that many of the failures were actually reactivations of old deep-seated landslides after land use changes. Therefore, this study was conducted (1) to explore the importance of environmental factors controlling landslide occurrence and (2) to estimate future landslide susceptibility. A landslide inventory map of the study area derived from aerial photograph interpretation and field checks shows the location of 57 landslides and six zones with multiple landslides, mainly complex slides and debris flows. In total 14.8% of the area is affected by an old landslide. For the landslide susceptibility modelling, weights of evidence (WofE), was applied and five different models were produced. After comparison of the models and spatial validation using Receiver Operating Characteristic curves and Kappa values, a model combining data on elevation, hillslope gradient, aspect, geology and distance to faults was selected. This model confirmed our hypothesis that deep-seated landslides are located on hillslopes with a moderate slope gradient (i.e. 5°–13°). The depletion areas are expected on and along the border of plateaus where weathered basalts rich in smectite clays are found, and the landslide debris is expected to accumulate on the Amba Aradam sandstone and upper Antalo limestone. As future landslides are believed to occur on inherently unstable hillslopes similar to those where deep-seated landslides occurred, the classified landslide susceptibility map allows delineating zones where human interventions decreasing slope stability might cause slope failures. The results obtained demonstrate that the applied methodology could be used in similar areas where information on the location of landslides is essential for present-day hazard analysis. 相似文献
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2010-08-07-08发生的甘肃舟曲特大泥石流造成了1 765人死亡和失踪,33幢面积共11.472 km2的建筑物被直接冲毁,有20幢面积约69 km2建筑被部分损坏.现场的调查表明,泥石流破坏建筑物主要有冲击、淤埋和摩擦三种方式.通过对8座破坏建筑物的具体分析,发现泥石流破坏建筑物有正向以撞击为主、侧向以淤埋和摩擦为主,沿流向呈现波浪式变化以及遮蔽效应等特点.根据泥石流的破坏方式、特点和建筑物类型,初步提出了我国山区居民住宅两种常见结构的泥石流破坏分级标准.最后提出了几条能有效减轻泥石流对建筑物破坏的具体措施,可供坐落于泥石流危险区的山区城镇借鉴. 相似文献
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1556年华县大地震的次生灾害 总被引：1，自引：0，他引：1
陕西华县于1556-01-23(明嘉靖三十四年十二月十二日)深夜,发生里氏814级地震,死亡83万人,成为世界罕见的特大灾难。地震期间和地震以后,由于震动荷载作用,地震区岩石破碎,发生了大范围崩塌灾害,为水石流发育提供了丰富的固体物质。震后450 a(1556~2006年)以来,这些碎屑物质在暴雨激发下,多次暴发水石流,在山前洪积扇和平原地区,造成了严重灾害和巨大损失;同时,也形成了地形上的淤积,改变了局部地形条件,使得该区容易遭受洪水灾害。1960年三门峡大坝建成蓄水之后,渭河下游淤积了大量泥沙,河床抬升,成为地上河,与从秦岭北坡沿溪流出山口向下发育的洪积扇共同作用,形成了地形相对下凹的"二华夹槽",这里常受洪水侵袭,损失巨大,严重危害人民生命财产安全,影响经济发展。 相似文献
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Contrasting rainfall generated debris flows from adjacent watersheds at Forest Falls, southern California, USA 总被引：1，自引：0，他引：1
Debris flows are widespread and common in many steeply sloping areas of southern California. The San Bernardino Mountains community of Forest Falls is probably subject to the most frequently documented debris flows in southern California. Debris flows at Forest Falls are generated during short-duration high-intensity rains that mobilize surface material. Except for debris flows on two consecutive days in November 1965, all the documented historic debris flows have occurred during high-intensity summer rainfall, locally referred to as ‘monsoon’ or ‘cloudburst’ rains. Velocities of the moving debris range from about 5 km/h to about 90 km/h. Velocity of a moving flow appears to be essentially a function of the water content of the flow. Low velocity debris flows are characterized by steep snouts that, when stopped, have only small amounts of water draining from the flow. In marked contrast are high-velocity debris flows whose deposits more resemble fluvial deposits. In the Forest Falls area two adjacent drainage basins, Snow Creek and Rattlesnake Creek, have considerably different histories of debris flows. Snow Creek basin, with an area about three times as large as Rattlesnake Creek basin, has a well developed debris flow channel with broad levees. Most of the debris flows in Snow Creek have greater water content and attain higher velocities than those of Rattlesnake Creek. Most debris flows are in relative equilibrium with the geometry of the channel morphology. Exceptionally high-velocity flows, however, overshoot the channel walls at particularly tight channel curves. After overshooting the channel, the flows degrade the adjacent levee surface and remove trees and structures in the immediate path, before spreading out with decreasing velocity. As the velocity decreases the clasts in the debris flows pulverize the up-slope side of the trees and often imbed clasts in them. Debris flows in Rattlesnake Creek are relatively slow moving and commonly stop in the channel. After the channel is blocked, subsequent debris flows cut a new channel upstream from the blockage that results in the deposition of new debris-flow deposits on the lower part of the fan. Shifting the location of debris flows on the Rattlesnake Creek fan tends to prevent trees from becoming mature. Dense growths of conifer seedlings sprout in the spring on the late summer debris flow deposits. This repeated process results in stands of even-aged trees whose age records the age of the debris flows. 相似文献
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Major debris-flow deposits occur along the xerothermic valley of the upper Jinsha River. The debris-flow deposits, ranging in thickness from 1 to 20 m, invariably occupy gently inclined piedmont slopes. The sediments are presently deeply dissected by gullies, and the process of mass movement has almost ceased. Detailed textural, stratigraphical, and geochemical studies reveal the formation processes of the debris flows. Seven debris-flow incidents are noted based on the unit combination characteristics of debris-flow deposits. The age estimates of optically stimulated luminescence (OSL) show that the occurrence of debris flows started at around 10.6 kyr BP and weakened until 4.5 kyr BP, corresponding to the obvious strengthened phase of the summer monsoons in the region. The ages of the debris-flow deposits indicate that the occurrence of a mass of debris flows was a response to the intensified summer monsoon in the SE fringe of the Tibetan Plateau since the early Holocene. 相似文献