谷坊在泥石流防治中的作用--以云南蒋家沟2条支沟的对比为例

泥石流灾害严重威胁其影响区人民的生命和财产安全,但是泥石流灾害可以通过诸如控制侵蚀等工程措施来预防或者减轻。谷坊正是能够在泥石流形成区对泥石流灾害进行有效防治的工程措施之一。在野外实地调查的基础上,运用构造地质、工程地质、岩土力学等理论和方法,对比云南蒋家沟泥石流的2个主要支沟——门前沟(有谷坊布设)和多照沟(没有谷坊布设)在沟床纵坡降、沟谷两侧斜坡稳定性及泥石流侵蚀速率等3个方面的差异,来说明谷坊工程能够有效抬高泥石流侵蚀基准面,降低泥石流沟谷回淤段沟床纵坡及由此带来的泥石流流速的降低和能量的耗散,固定沟床、稳定岸坡、促进植被生长,最终达到防治泥石流的目的。此外,还讨论了谷坊设计时需要注意的几点问题。     

云南本屋宅箐泥石流沟特征及危险性评价

文章以云龙县宝丰乡福利村本屋宅箐泥石流沟为研究对象,在现场实地调查的基础上,阐述泥石流沟特征、类型、成因、发展趋势,并对该泥石流沟的危险性进行了评价。该泥石流的形成受地质、地形、气象水文及人类活动等综合因素的影响,前期降雨使固体物质分散汇入沟床积累,属于崩塌+滑坡型、沟谷泥石型、中型、高频、发展期稀性泥石流。目前,福利村本屋宅箐流域固体物源丰富,降雨集中,水源充沛,溯源侵蚀作用强烈,物源区滑坡、沟岸坍塌发育,谷坡稳定性差,泥石流的发展有增强趋势。本次采用成都山地所刘希林于1996年提出的单沟泥石流危险度评价方法对该泥石流沟的危险性进行评价,单沟泥石流危险度H单=0604,按照分级标准,福利村本屋宅箐泥石流沟属高度危险泥石流沟。     

FCM(模糊C-均值聚类)法在泥石流分类中的应用

影响泥石流沟性质的因素繁多,如主沟长度、流域面积、流域最大高差等,故泥石流的分类是受诸多因素影响的多维非线性问题,对泥石流分类可以对泥石流危险度划分及防治对策等提供较好的建议,本文结合FCM(模糊C均值聚类)法,根据现场调查的泥石流沟各因素值划分泥石流沟的类别,以现场调查及工程经验证明分类结果较好反映泥石流沟的实际情况,证明了该方法的有效性及可行性。     

The importance of gully flow modelling to urban flood simulation

ABSTRACT

Urban flood simulation often ignores or simplifies the function of underground gully systems due to data and computational limitations. To discover the influence of gullies on urban flooding, a novel approach is proposed in this study, by fully-coupling a 1D gully flow model (GFM), a 1D sewer flow model (SFM), and a 2D overland flow model (OFM) to simultaneously simulate the flow exchanges between surface, gullies and sewer pipes. This fully-coupled approach is compared with a simplified approach which directly introduces surface water into sewer pipes without being via gullies. The validation results show that the fully-coupled approach considerably reduces the underestimation of flood extent by 27% compared with the simplified approach. Without considering the capacity of lateral tubes between gullies and sewer pipes, the simplified approach over-drains the surface water into sewer pipes. The modelling of gully flow is crucial for correctly evaluating the efficiency of drainage systems.     

石笼拱柔性拦截坝新技术及其数值模拟

针对常见的泥石流拦挡结构被冲击破坏的问题,提出了柔性石笼拱拦截坝新技术。柔性石笼拱以石笼为主要材料,砌筑成拱形,上游面铺设废旧轮胎防冲垫层,拦截泥石流。利用ANSYS LS-DYNA软件,分析了柔性石笼拱结构对泥石流冲击的动力响应,并与刚性浆砌石结构进行对比。通过MIDAS GTS软件计算,分析了石笼拱拦蓄泥石流后孔隙水压力变化及静力稳定特性。数值计算结果表明,柔性石笼拱结构能合理地优化结构受力,变形自适应,减小巨石冲击荷载以及饱和泥石流的浆体压力对结构的不利影响。     

Effectiveness of check dams in the control of general transitory bed scouring in semiarid catchment areas (South-East Spain)

The semiarid areas of the Spanish Mediterranean region are environments that are severely threatened by desertification. Hydrological-forestry restoration is a very useful tool to fight these processes in programmes and projects of basin management. Check dams particularly can control bed erosion in ephemeral channels, among other things. The main aim of this study, then, is to evaluate how much check dams influence the degree of transitory general scouring in dry alluvial channels that function only sporadically and as torrents. Two areas were chosen: the Cárcavo and Torrecilla catchments (River Segura basin), both drained by ephemeral gullies and both having undergone hydrological correction projects during the 1970s. Equations based on grain bed movement commencement criteria were applied for floods of different water depths, bearing in mind bed texture changes and slope adjustment brought about by dam construction. The results are contrasted with the critical velocity values, which in turn depend on the flow depth and the cross-section area before flooding. Finally, a comparison between real and predicted scouring is established for the cases analysed, including bankfull flow. Especially, the usefulness of Neill's method has been tested in relation to net erosion values measured in the field with successful results.     

Debris flow simulation 2D (DFS 2D): Numerical modelling of debris flows and calibration of friction parameters

Debris flows are rapid mass movements with a mixture of rock, soil and water. High-intensity rainfall events have triggered multiple debris flows around the globe, making it an important concern from the disaster management perspective. This study presents a numerical model called debris flow simulation 2D (DFS 2D) and applicability of the proposed model is investigated through the values of the model parameters used for the reproduction of an occurred debris flow at Yindongzi gully in China on 13 August 2010. The model can be used to simulate debris flows using three different rheologies and has a user-friendly interface for providing the inputs. Using DFS 2D, flow parameters can be estimated with respect to space and time. The values of the flow resistance parameters of model, dry-Coulomb and turbulent friction, were calibrated through the back analysis and the values obtained are 0.1 and 1000 m/s², respectively. Two new methods of calibration are proposed in this study, considering the cross-sectional area of flow and topographical changes induced by the debris flow. The proposed methods of calibration provide an effective solution to the cumulative errors induced by coarse-resolution digital elevation models (DEMs) in numerical modelling of debris flows. The statistical indices such as Willmott's index of agreement, mean-absolute-error, and normalized-root-mean-square-error of the calibrated model are 0.5, 1.02 and 1.44, respectively. The comparison between simulated and observed values of topographic changes indicates that DFS 2D provides satisfactory results and can be used for dynamic modelling of debris flows.     

北京市延庆区石窑村南地沟泥石流特征及发展趋势预测

本文以北京市延庆区石窑村南地沟泥石流为研究对象,通过野外调查与GIS统计分析,研究该流域降雨条件、地形地貌和沟道条件、物源条件等形成条件特征,针对流域内松散堆积物转换,开展了流域分区特征分析;通过14个因子分析,建立了该泥石流的发育阶段识别模型,对其发展趋势进行了预测;利用单沟泥石流堆积区公式开展了最大危险区预测研究,提出相应的防治措施建议。研究表明:石窑村南地沟泥石流内松散堆积物动储量达18.36×10~4 m~3,物源类型划分为冲洪积物源、残坡积物源、人工堆积物源和崩滑塌物源4种,其中残坡积所占比重最大。该泥石流属于暴雨-沟谷型-支沟群发型、中易发泥石流,泥石流发展阶段处于发育期,最大危险区面积为0.413 km~2,对沟口堆积区的石窑村及村民的生命财产安全造成威胁,建议采用局部物源平整与疏理排导渠相结合的综合治理措施。本文为该区地质灾害防治提供基础依据。     

甘肃临泽县地质灾害类型及特征

甘肃省张掖市临泽县是河西走廊地质灾害最为发育的县区之一。通过实地测量、调查评价和综合研究等手段,在概述县域自然地理条件及地质背景的基础上,县域内已有的地质灾害共30处,其中泥石流沟29条主要集中分布于祁连山和合黎山山前与走廊平原的过渡带,尤其是北部合黎山山前连片分布;崩塌1处为斜坡坡度65°的独山子崩塌。从地形条件、物质条件、降雨条件以及人类日益工程建设活动等方面研究表明,较大的沟床纵坡降比和流域面积、丰富的松散固体物质和短时间聚集的充足水源(多是有暴雨形成)是形成区内泥石流的基本条件。崩塌(不稳定斜坡)于公路沿线的人工开挖坡度大于60°的边坡地带。临泽县地质灾害具有不均匀性、突发性、周期性。该研究为县域地质灾害防灾减灾提供科学依据。     

土工离心机模拟泥石流问题的相似性考虑

尺度效应是阻碍对泥石流复杂动力学过程理解的最主要因素。土工离心机通过提供一个等效的高倍重力加速度场,能够在模型中还原岩土工程原型的应力状态,为泥石流物理模拟的尺度效应难题提供了一个经济可行的解决方案。在总结前人提出的两相流（泥石流）无量纲参数的基础上,建立了应用于土工离心机模拟泥石流的分层次相似性试验设计体系,可以确保模型和原型中泥石流运动学与动力学参数绝对值和相对值的一致,从而可以系统性地还原泥石流原型问题的物理过程。同时,针对对模拟结果产生较大影响的科里奥利效应和1g自然重力加速度,建议试验设计阶段选择有效旋转半径更大的离心机并适当降低旋转角速度。研究结果对泥石流和碎屑流的小尺度、大尺度物理模拟以及离心机模拟具有理论和技术层面的参考意义。     

The geomorphological comparison of two debris flows and their triggering mechanisms

 The paper reports on debris flows in the Tungmen and Hoser areas of Taiwan, triggered by Typhoon Ofelia on 23 June 1990 and Typhoon Herb at the end of July 1996 respectively. The intense rainfall resulted in large volumes of debris being eroded from the valleys. The village of Tungmen was almost totally destroyed by in excess of 100,000 m³ of material which was moved by the 1990 debris flow while the 1996 typhoon was responsible for the movement of almost 1.5 million m³ of material, 80% of which extended to the confluence area of the two side gullies and the Hoser River. Attention is drawn to the change in shape of the valley sides from generally V-shaped prior to the debris flow to U-shaped following the storms. A comparison of aerial photographs as well as field data was used to define the main topographical effects of the 1990 storm (Tungmen) and 1996 event (Hoser). A study of the discontinuity pattern within the valleys emphasised the significance of toppling and gravity slumping of material in the sides of the valleys in producing large quantities of debris which, in heavy storm conditions, can flow down the gullies. Laboratory tests were used to simulate the effect of saturation on the materials. These indicated that in their saturated state they would easily become unstable. Received: 1 December 1999 · Accepted: 11 January 2000     

Rainfall-triggered debris flows following the Wenchuan earthquake

On 24 September 2008, 72 debris flows were triggered by heavy rainfall in the central part of the area affected by the Wenchuan Earthquake. This paper describes the process of debris-flow initiation and transport in the study areas and presents field observations on the roles of rainfall, lithology and the presence of faults. It is likely that following the ground shaking, the critical amount of accumulated precipitation and the hourly rainfall intensity necessary to initiate debris flow was reduced compared with values before the earthquake. A case study in the Xishanpo gully is presented; the debris flow from which caused a thick accumulation in the already devastated city of Beichuan. It is concluded that the whole of the area shaken by the Wenchuan Earthquake is now more susceptible to debris flows, which may be initiated by localized heavy rainfall. Care must be taken to properly assess this new type of geo-hazard.     

A hydraulic soil erosion model based on a weakly compressible smoothed particle hydrodynamics method

Hydraulic soil erosion is one of the most important natural phenomena driving terrain changes over time. It is associated with a variety of geoenvironmental hazards such as coastline retreat, soil loss and debris flows, and can have severe consequences. In this work, an erosion criterion was introduced to analyze the water–sediment interaction, and a hydraulic soil erosion model was then established based on the smoothed particle hydrodynamics (SPH) method. Numerical simulations of dam-break flow on a mobile bed and sediment flushing were carried out, and the performance of the hydraulic erosion model was evaluated. The numerical results matched the experimental data well, thus verifying the reliability and validity of the proposed model.

     

考虑分界面的黏性泥石流下游演进数学模型研究

基于分界面理论,以泥石流屈服深度对应的面为分界面,将黏性泥石流分为理想流体和Bingham流体,建立了模拟黏性泥石流演进过程的数学模型和相应计算方法。该模型基于泥石流的运动特征,注重不同层间泥石流流速的差异,并可合理反映泥石流运动速度对其演进形态的影响机制;同时,全面考虑了黏性泥石流在演进过程中所呈现的"舌状体"和"龙头"由上向下翻落现象,因此可更准确描述黏性泥石流在演进过程中的运动状态。采用3组模型试验结果对建立的数学模型与计算方法进行了验证,结果表明:模型计算得出的泥石流泛滥范围和最大堆积厚度与模型试验结果误差在±5%以内,验证了模型的合理性。     

大渡河某泥石流沟形成机制及其工程效应研究

结合大渡河某泥石流沟发生的大规模泥石流灾害，阐述了泥石流的发育历史，对该泥石流沟各功能区进行了详细的工程地质调查分析，研究了该泥石流沟形成机制及带来的工程效应影响，指出应防范泥石流的发生，从而减小对沟口桥梁及公路的影响。     

北京市延庆地区水泉沟村车道沟泥石流发育特征及动力学研究

本文以北京市延庆地区水泉沟村车道沟泥石流沟为研究对象,通过泥石流精细调查及资料统计,研究该泥石流发育特征和形成条件,在分析流域内松散堆积物补给特征的基础上,综合研究了该泥石流的动力学特征,进而开展泥石流危险区预测评价,提出相应的防治措施建议。研究结果表明:该泥石流沟内可参与泥石流活动的松散堆积物动储量为20.79×10⁴m³,分为冲洪积、残坡积、人工堆积和崩滑塌等4种补给来源,其中人工堆积所占比重最大;经动力学分析,洪峰流量值在10年一遇的降雨条件下为17.03m³/s,20年一遇的降雨条件下为19.21m³/s,50年一遇的降雨条件下为22.10m³/s,100年一遇的降雨条件下为24.28m³/s,一次固体冲出总量分别为0.55×10⁴m³、0.63×10⁴m³、0.72×10⁴m³、0.79×10⁴m³,属于小型泥石流,最大危险区面积为0.2763km2。通过评价分析,该泥石流沟仍存在爆发小型泥石流的可能性,将对下游车道沟村以及行车和行人的生命财产安全造成威胁。研究成果可为延庆地区该类泥石流单沟预警模型研究和灾害防治提供科学依据。     

盐源县塘房沟泥石流成因及运动特征研究

在现场勘察调查的基础上,对塘房沟泥石流的形成条件和流体的动力学特征作了较详细的分析,得出了对沟口村庄进行搬迁和对塘房沟治理工作迫在眉睫的结论,研究成果为泥石流防治工程提供了可靠的设计依据。     

北京市延庆区秤勾湾沟泥石流特征及预警雨量研究

本文以北京市延庆区秤勾湾泥石流沟为研究对象,利用泥石流沟精细调查及历史资料,研究其降雨特征、流域特征、分区特征、物源特征,采用灰色系统关联度方法开展危险性评价研究,建立URCS-CN预警雨量模型,开展预警雨量阈值研究。研究结果显示:秤勾湾泥石流沟危险性评分为0.84分,危险等级为高危险,流域内红色预警过程雨量122 mm、橙色预警过程雨量109 mm、黄色预警过程雨量95 mm、蓝色预警过程雨量82 mm;秤勾湾沟泥石流累计流量与预警流量呈线性关系,前期的有效降雨与短时强降雨呈彼增我减的态势,在红色预警范围左侧为泥石流灾害的低频区,红色预警范围为泥石流灾害的高频区。研究成果为延庆地区该类泥石流单沟预警模型研究和灾害防治提供科学依据。     

A further discussion of the factors controlling the distribution of Pt, Pd, Rh and Au in road dust, gullies, road sweeper and gully flusher sediment in the city of Sheffield, UK

Forty paired road dust and gully sediments from the city of Sheffield in NE England show that high platinum, palladium and rhodium concentrations derived from catalytic converters depend on proximity to both roundabouts rather than traffic lights and to topographic lows. Road dust outside schools and control samples, further away on the same road, show that Pt, Pd and Rh concentrations are dependant on passing traffic flow rather than numbers of stopping vehicles. Highest values of Pt + Pd in road dust are 852 ppb and 694 ppb in gullies. Rh has maximum values of 113 ppb in road dust and 49 ppb in gullies. Pt and Pd values of a few ppb to just over 100 ppb occur in road dust where traffic does not stop, on roads away from junctions. Pt, Pd, Rh and Au are all picked up by road sweepers and gully flushers both with maximum values of just over 100 ppb Pt and Pd. High Au values (maximum 610 ppb in a road dust) were located on pavements, in suburbs, outside schools and in road sweepers collecting in residential areas rather than on high traffic flow roads. Stratification of Pt and Pd in gullies was not observed whereas a high Au value was recorded at the bottom of a gully suggesting gravity concentration for Au. Anomalous Pd grades of 1050 ppb in road dust from a school entrance and 2040 ppb in a street sweeper sample were recorded. These high Pd- and Au-bearing samples do not have anomalous Pt or Rh values and may be sourced from jewellery or dental fillings. However, most samples have consistent Pt/Pd ratios of about 1 and Pt/Rh values of 4 to 5 indicating a catalytic converter source. Pt and Pd are concentrated in road dust at levels well above background in all the samples, including on high and low traffic flow roads.     

北京碰河寺沟泥石流成因及综合防治对策

北京地区泥石流主要分布在密云区北部、怀柔区中部、延庆区东部及房山、门头沟区西部地区。北山泥石流受区域构造和山势走向所控制,总体呈北东向展布,其无论爆发频率、活动规模及发育密度均为北京山区之首位。研究区位于密云区东北部,为北山地区的一条老泥石流沟,曾在1976年发生过泥石流活动,支沟沟口处赵洪全一家房屋被冲毁,其它损失情况不详。2011年7月24日,碰河寺沟主沟发生特大山洪,将进村道路冲毁、毁坏房屋数十间、冲毁良田、果木上百株,造成造成巨大的经济损失,进行治理已是迫在眉睫。