崩塌体水力输移与塌岸淤床交互影响试验

以二元结构河岸崩塌模式为研究背景,在弯道水槽中展开系列试验,研究凹岸坡脚处成型崩塌体在水力作用下输移过程及其对岸坡稳定性与河床冲淤的交互影响。试验成果表明,崩塌体经水力分解破碎呈块状、片状或颗粒状起动,部分随水流带至凸岸或下游,堆积在坡脚附近的崩塌体残留量随水力作用大小及土体特性不同而变化。崩塌体临水面周围尤其上下游端水流紊动强烈易形成较大剪切力区,临坡面上下游端附近剪切力较无崩塌体时减小;崩塌体体积越大,对剪切力区特征的改变也越明显。崩塌体的存在虽不能制止附近岸坡的再次崩塌,但可能抑制崩岸发展及附近河床淤积的程度,崩塌体的粘性或体积越大,这种抑制作用越显著;相同崩塌体抑制附近河床淤积的程度较抑制岸坡崩塌的程度大。     

均质土岸坡崩塌与河床冲淤交互过程试验

在弯道水槽中展开系列试验,研究水力冲刷过程中均质土岸坡冲刷崩塌输移与河床冲淤过程及其影响因素。该过程及变化特征可描述为:水下坡面侵蚀及坡脚淘刷导致岸坡失稳崩塌;暂时堆积在凹岸坡脚处的崩塌体加剧附近水流紊动程度利于其输运与分解;分解后较粗的颗粒随弯道螺旋流以推移质形式被输移至下游凸岸落淤,较细的颗粒大部分都随水流以悬移质形式被携带至下游出口;水流结构随岸坡及河床变形而调整;如此循环往复。试验成果进一步表明:冲刷状态下,试验材料黏性越小、近岸流速越大、作用时间越长,岸坡冲刷崩塌量及河床冲刷量都越大;同条件下岸坡冲刷崩塌总量大于河床冲刷总量,且河床相对冲刷率随岸坡冲刷崩塌量的增大而减小,数值范围为0.40~0.92。     

磨西河泥石流堵断大渡河物理模拟与早期识别

历史记录与堆积区证据显示,四川泸定磨西河泥石流历史上堵断大渡河事件易发、频发,为泥石流堵河的典型案例。为了深入剖析磨西河泥石流相关物理参数对其入汇主河运动过程的影响,本文采用1∶500几何相似模型进行了物理模拟试验,结果表明:1)泥石流密度、流量比对泥石流堵河影响程度大,其均与泥石流堵河程度显著正相关,密度、流量比越大,堵河程度越严重,且存在发生堵河事件的临界点;2)流速比对堵塞影响程度小;3)磨西河堵断大渡河的早期识别指标为,当磨西河泥石流流量大于2 000 m3/s,泥石流物质组成为漂卵石混中粗砂、少含水时,磨西河泥石流易发生堵断大渡河的危害。磨西河泥石流堵断大渡河事件具有很强的偶然性与不确定性,本文仅选取磨西河与大渡河交汇区开展物理模拟试验,通过试验获取影响堵河发生的单因子临界值进行堵河早期识别,可能存在一定误差,但不失为堵河判别方法的创新,具有一定的实践意义,也为相关泥石流入汇主河早期识别理论与试验研究提供了技术方法。     

四川省都江堰市“8.13”干沟泥石流特征及成因

采取野外调查方法对干沟泥石流的分布和特征进行调查,分析泥石流形成区的地形条件和物源条件,以及流通区和堆积扇的特征。探讨泥石流起动和输移过程,分析泥石流形成的降雨、岩石和断层作用,计算泥石流特征值。     

沙质河床冲刷过程中床沙级配的模拟

研究了沙质河床冲刷过程中床沙级配的模拟方法。在该方法中采用了新的描述床沙级配变化的动力学方程和床沙级配在交换层内垂向变化与水流强度、河床冲刷强度的关系,反映了冲刷过程中交换层内向床面补充的物理过程。通过室内实验率定了相关参数,建立了床沙级配变化动力学方程的数值求解方法,模拟了床沙冲刷粗化。计算结果与室内实验结果符合较好,表明所建议的方法反映了河床冲刷中床沙级配变化的物理事实,可用于沙质河床冲刷粗化模拟。     

推移质翻越低坝输移特性的试验研究

对于山区河流低坝而言，平时淤积在坝前的推移质粗沙可能会在洪水期集中翻越坝顶，形成高强度输沙。本文开展水槽试验，研究推移质粗沙自上游起动、推进、再翻越坝顶后向下游输移的过程，分析了输沙参数的变化特性及数理规律，描述了翻坝输沙模式及运动特征，揭示了输沙规律与河床形态之间的自然联系。取得如下认识：①输沙量随时间大致以幂函数规律增长。②低坝附近区域河床形态终将趋于稳定，上游和下游均形成相对稳定的曲面斜坡淤积体。③在不同的水流强度下推移质翻坝输移模式存在差异。对于一般水流强度工况，上游淤积体曲面斜坡表面泥沙颗粒以滚动或滑动模式起动，推移至接近坝顶位置时再跃移翻坝，后向下游输移；对于更高水流强度工况，后期的翻坝输沙模式可能发生显著转变，周期性边壁漩涡成为翻坝输沙的主要动力来源。     

泥石流堆积运动特征分析

以云南省东川市深沟泥石流堆积区为研究对象, 根据深沟可能爆发泥石流灾害的区域范围、规模、性质和介质特征, 按爆发20年一遇(频率5%)和100年一遇(频率1%)的泥石流灾害预测规模, 运用数值模拟方法模拟了泥石流爆发历时过程的堆积运动特征及空间分布形态; 分析了不同规模泥石流堆积运动过程中, 泥石流堆积厚度及堆积运动速度在空间上和时间上的变化发展趋势.      

山东蒙山九龙潭冰川堆积“垄槽序列”的特征及演化过程研究——兼论冰川、泥石流堆积序列的差异性

中国东部中低山区是否存在第四纪冰川已经争议了一个世纪，作为东部地区冰川堆积重要依据的"泥砾"（冰碛），一直被持非冰川观点者称作是泥石流沉积物。但是，由于冰川与泥石流的堆积过程之间存在本质差别，这必然在堆积体的特征上表现出专属性差异。因此建立冰川与泥石流在堆积特征与堆积过程上的专属性差异，在冰碛物的成因分析、冰碛堆积过程恢复上就有着重要意义。文章在对比分析了冰川堆积与泥石流堆积的过程差异的基础上，发现两类堆积体在平面与剖面上都存在明确的专属性差别。冰川冰碛在平面上形成专属性的垄槽序列，剖面上显示为无层理、混杂堆积状态。泥石流形成堆积扇，扇面上呈放射状垄岗堆积，剖面上表现为韵律序列。这是区别冰川与泥石流堆积体的本质所在。在此基础上，对蒙山九龙潭一带混杂堆积体进行调查与恢复，发现其具有典型的冰川成因垄槽序列特征，结合其剖面上表现为无层理、混杂堆积特征，从沉积序列与沉积过程的角度，佐证了蒙山九龙潭混杂堆积为第四纪冰川作用的事实。垄槽序列既是堆积物是否为冰川作用属性判断的专属性特征，也是恢复冰碛堆积体基本地貌特征与堆积过程的理论基础。      

输移型泥沙灾害及其特征初步研究

近年来,泥沙灾害越来越引起人们的重视.输移型泥沙灾害是泥沙灾害的子类型.本文提出了输移型泥沙灾害的基本概念,并对输移型泥沙灾害的类型和特征进行了初步的探讨.根据输移介质的不同,输移型泥沙灾害可进一步分为风力输移型和水力输移型泥沙灾害.风力输移型泥沙灾害主要包括浮尘、扬沙、沙尘暴和沙丘移动等,这类泥沙灾害主要发生在干旱-半干旱地区,但影响范围很广.以水流为搬运介质的输移型泥沙灾害主要有泥石流灾害、高含沙水流灾害和一般挟沙水流灾害,另外还有以水为介质,以重力搬运作用为主的泻溜、土体蠕动等灾害.水力输移型泥沙灾害仅限于流域,涉及范围较小,出现的频率较低、幅度较小,其灾害表现形式为在冲刷、淤积和河床演变过程中对人类产生危害,具有伴生性、潜在性、突发性和链锁性等特征.     

房山周口店车厂北沟泥石流特征及防治

泥石流是北京地区危害性严重的地质灾害之一,作为北京"7·21"特大暴雨灾害受灾最为严重的区县,房山区近现代泥石流一直比较活跃,灾情严重。为了查清房山区"7·21"特大暴雨后典型泥石流灾害发育和运动特征,本文选取了车厂村北沟作为样本,通过采用现场调查、槽探、岩土测试等方法,对主沟整体流域进行了系统研究。从而查清了形成区的物源类型和可移动物源储量,掌握了全流域的沟道形态特征;通过对堆积区堆积形态和堆积物调查分析,论述了主沟水动力特征和冲淤特征;根据相关规范,计算得出了泥石流的动力学参数。分析了泥石流形成机理,进行了危险性评价,提出了防治对策。     

Debris-flow simulations on Cheekye River, British Columbia

Cheekye River fan is the best-studied fan complex in Canada. The desire to develop portions of the fan with urban housing triggered a series of studies to estimate debris-flow risk to future residents. A recent study (Jakob and Friele 2010) provided debris-flow frequency-volume and frequency-discharge data, spanning 20-year to 10,000-year return periods that form the basis for modeling of debris flows on Cheekye River. The numerical computer model FLO-2D was chosen as a modelling tool to predict likely flow paths and to estimate debris-flow intensities for a spectrum of debris-flow return periods. The model is calibrated with the so-called Garbage Dump debris flow that occurred some 900  years ago. Field evidence suggests that the Garbage Dump debris flow has a viscous flow phase that deposited a steep-sided debris plug high in organics in centre fan, which then deflected a low-viscosity afterflow that travelled to Squamish River with slowly diminishing flow depths. The realization of a two-phase flow led to a modelling approach in which the debris-flow hydrograph was split into a high viscosity and low viscosity phase that were modelled in chronologic sequence as two separate and independent modelling runs. A perfect simulation of the Garbage Dump debris flow with modelling is not possible because the exact topography at the time of the event is, to some degree, speculative. However, runout distance, debris deposition and deposit thickness are well known and serve as a good basis for calibration. Predictive analyses using the calibrated model parameters suggest that, under existing conditions, debris flows exceeding a 50-year return period are likely to avulse onto the southern fan sector, thereby damaging existing development and infrastructure. Debris flows of several thousand years return period would inundate large portions of the fan, sever Highway 99, CN Rail, and the Squamish Valley road and would impact existing housing development on the fan. These observations suggest a need for debris-flow mitigation for existing and future development alike.     

基于HBP本构模型的泥石流动力过程SPH数值模拟

本构模型是描述泥石流流变特性的关键,也是决定其动力过程数值模拟准确性的核心问题之一。泥石流流体属多相混合物,现有的研究已证实其存在剪切增稠或剪切变稀的现象,传统基于Bingham及Cross线性本构关系的数值模型难以准确描述泥石流流变特性。文中探讨了Bingham模型在低剪应变率下的数值发散问题,在光滑粒子流体动力学（SPH）方法框架上建立了整合Herschel-Bulkley-Papanastasiou(HBP）本构关系的稀性泥石流动力过程三维数值模型。相比传统基于浅水波假设的二维数值模型,所述方法从三维尺度建立SPH形式下的泥石流浆体纳维?斯托克斯方程并进行数值求解,可获取泥石流速度场时空分布及堆积形态,同时采用HBP本构关系描述泥石流流变特性,能在确保数值收敛的前提下反映泥石流流体在塑性屈服过渡段及大变形状态下应力?应变的非线性变化。为验证提出方法的合理性,结合小型模型槽实验观测进行了对比,结果表明数值模拟与实测结果基本吻合。     

基于旋转水槽试验的水下泥石流底部水压研究

水下泥石流的低阻力运动特性研究是研究水下泥石流运动机理的重要内容,水下泥石流底部的水压对泥石流运动阻力有重要影响。为此,采用旋转水槽实验室模拟水下泥石流的低阻运动,实测水下泥石流视摩擦角;采用新开发的测量系统,实测水下泥石流底部的水压,评估水下泥石流底部的静水压和附加水压。试验结果和理论分析表明,在水下泥石流底部的附加水压与水下泥石流的低阻力运动密切相关:水下泥石流密集流的最大厚度为12 mm的条件下,附加水压最大值达69 Pa。研究成果为揭示水下泥石流低阻力运动机理提供实验依据,新开发的测量系统为低阻力运动泥石流的水压测量开辟新途径。     

Characteristics of two Pleistocene channel-fill deposits and their implication on the interpretation of megasequences in ancient sediments

Two Pleistocene channel fills located in two different geological settings, on Guadeloupe in the lesser Antilles and along the Coppermine River in the Northwest Territories of Canada, have different clast compositions, scale, and origin of fragmentation but have similar depositional characteristics. Massive bedding or absence of structures caused by traction, sharp non-erosive contacts, reverse coarse-tail grading, matrix-supported clasts together indicate a debris-flow mechanism in which mixtures of fine and coarse sediments moved downslope by laminar flow. Field evidence suggests subaqueous deposition for both deposits. Both bed thickness (BTh)/maximum grain size (MGS) ratios and correlations appear characteristic of subaqueous masses capable of flowing on slopes less than 1°. The two channel fills have random BTh and MGS variations, they do not thin and fine up-section. It is suggested that fills originating from laminar mass transport could normally have random BTh and MGS up-section variations. In flysch and volcaniclastic sequences, where coarse sediments interpreted as laminar flow deposits are common, up-section BTh and MGS variations may result from processes related to source, slope, and flow characteristics rather than from the environment in which the sediments accumulate (channel).     

滦平盆地陡坡带下白垩统西瓜园组水下粗碎屑岩沉积特征及搬运机制

为探讨陆相断陷湖盆陡坡带构造活动控制下水下粗碎屑岩沉积特征、搬运机制及其演化规律,以滦平断陷盆地陡坡带下白垩统西瓜园组为研究对象,采用无人机倾斜摄影、实测剖面、砾石定向性定量表征等技术方法,从沉积背景、岩相类型、沉积单元及相序特征等方面开展野外露头解剖工作.滦平盆地西瓜园组沉积时期,近岸水下扇沉积于构造沉降速率大、湖平面上升、深水、古地貌陡峭环境,洪水携带粗碎屑沉积沿陡坡带入湖,底部发育与地震活动相关的砾质碎屑流,伴随发育滑动—滑塌沉积,上部发育高密度浊流.随着沉积物不断供给,斜坡坡度逐渐减小;随着粗碎屑沉积搬运距离不断增加,砂砾质碎屑流中砾石表现出明显定向性,高密度浊流所占厚度比例增加;末端以低密度浊流为主.扇三角洲沉积于构造沉降速率相对较低、水深相对较浅、古地貌相对平缓的环境,发育相对成熟的供源体系,汇水系统长度较长,扇三角洲前缘粗碎屑岩由碎屑流向高密度浊流、牵引流、低密度浊流转换.      

The ability of debris, heavily freighted with coarse clastic materials, to flow on gentle slopes

Observations of many debris-flow deposits on gently-sloping alluvial fans have disclosed that debris commonly is heavily loaded with coarse clastic material and contains large isolated blocks. The paper describes how debris charged with coarse granular material can transport large blocks, yet flow on gentle slopes. Experimental results of mixing sand-sized particles with a slurry of clay plus water indicate that 45–55 vol. % of a single size, and up to 64% of two selected sizes, can be added before interlocking occurs. Theoretical analysis of multi-size classes suggest that 89 to more than 95 vol. % debris can be clastic materials without significant particle interlocking. The clay fraction, even if minor, plays a critical role in determining strength properties of debris. The mixture of clay plus water provides a cohesive slurry that supports fine-grained particles within the debris, as well as reduces the effective normal stresses between the particles. The increased unit weight of the clay plus water plus fine-grained particles allows the support of coarser grained particles. The pyramiding upon the clay-water slurry continues until the entire debris mass is supported in a virtually frictionless position because of the reduced effective normal stress and the lack of particle interlocking. Thus, the ability of debris flows to support large blocks can be understood in terms of the high unit weight of the displaced debris plus the strength of the fluid phase; that is, the blocks float in the debris as a result of a small density difference between the blocks and the debris, plus the cohesive strength of the clay-water slurry. Also, the ability of coarse clastic debris to flow on gentle slopes probably is a result of poor sorting of debris-flow materials which contain minor amounts of clay. The poor sorting allows the debris to have a high density yet have essentially no interlocking of clasts. The high density of the debris reduces effective normal stresses between clasts, thereby reducing apparent friction of the mixture.     

A discussion and classification of subaqueous mass-transport with particular application to grain-flow,slurry-flow,and fluxoturbidites

Sediments will remain at rest on the sea-floor provided forces of shear resistance exceed the downslope shear stress imposed by gravity. The shear resistance of granular water-saturated sediments is discussed within the constraints imposed by the Coulomb model of shear failure, and the phenomena of thixotropy, liquefaction, retrogressive flow sliding and fluidization are discussed as mechanisms for producing the mass-mobilisation of sediment. Processes of laminar mass-flow (= inertia flow) are broadly divided into those involving water as the interstitial fluid (grain-flow) and those having an interstitial fluid of enhanced viscosity (slurry-flow). Recent and experimental examples of inertia-flow are summarised and discussed under the headings grain-fall, grain-flow, slump-creep and fluxoturbidites. It is concluded that grain-flow and slump-creep deposits may be more widespread in the sedimentary record than present reports indicate. It is recommended that the term fluxoturbidite be restricted to its original sense, to describe the deposits of proximal turbidites in which the immediately pre-depositional transport was by inertia-flow. A suggested terminology for subaqueous mass-transport processes and their products is summarised in the form of a flow-chart, terminological distinction being drawn between the processes of mobilisation, transport and deposition of the sediment, and between the various sedimentary beds or facies that result from emplacement by mass-transport.     

Debris-flow event in the Frangerello Stream-Susa Valley (Italy)—calibration of numerical models for the back analysis of the 16 October, 2000 rainstorm

Three debris-flow simulation model software have been applied to the back analysis of a typical alpine debris flow that caused significant deposition on an urbanized alluvial fan. Parameters used in the models were at first retrieved from the literature and then adjusted to fit field evidence. In the case where different codes adopted the same parameters, the same input values were used, and comparable outputs were obtained. Results of the constitutive laws used (Bingham rheology, Voellmy fluid rheology and a quadratic rheology formulation which adds collisional and turbulent stresses to the Bingham law) indicate that no single rheological model appears to be valid for all debris flows. The three applied models appear to be capable of reasonable reproduction of debris-flow events, although with different levels of detail. The study shows how different software can be used to predict the debris-flow motion for various purposes from a first screening, to predict the runout distance and deposition of the solid material and to the different behaviour of the mixtures of flows with variation of maximum solid concentration.     

东营凹陷盐22块沙四上亚段砂砾岩粒度概率累积曲线特征

在岩芯观察和沉积相分析基础上,利用粒度分析资料对东营凹陷北部陡坡带盐22块沙四上亚段近岸水下扇砂砾岩体的粒度概率累积曲线进行了研究。研究表明,该地区近岸水下扇砂砾岩中的粒度概率累积曲线主要包括：＂上拱弧形＂、＂简单一段式＂、＂准牵引流型＂等3种基本类型和＂近似上拱弧形＂、＂台阶状多段式＂、＂低斜率两段式＂、＂低斜率三段...     

Comparison of numerical models of two debris flows in the Cortina d’ Ampezzo area,Dolomites, Italy

The accurate prediction of runout distances, velocities and the knowledge of flow rheology can reduce the casualties and property damage produced by debris flows, providing a means to delineate hazard areas, to estimate hazard intensities for input into risk studies and to provide parameters for the design of protective measures. The application of most of models that describe the propagation and deposition of debris flow requires detailed topography, rheological and hydrological data that are not always available for the debris-flow hazard delineation and estimation. In the Cortina d’Ampezzo area, Eastern Dolomites, Italy, most of the slope instabilities are represented by debris flows; 325 debris-flow prone watersheds have been mapped in the geomorphological hazard map of this area. We compared the results of simulations of two well-documented debris flows in the Cortina d’Ampezzo area, carried on with two different single-phase, non-Newtonian models, the one-dimensional DAN-W and the two-dimensional FLO-2D, to test the possibility to simulate the dynamic behaviour of a debris flow with a model using a limited range of input parameters. FLO-2D model creates a more accurate representation of the hazard area in terms of flooded area, but the results in terms of runout distances and deposits thickness are similar to DAN-W results. Using DAN-W, the most appropriate rheology to describe the debris-flow behaviour is the Voellmy model. When detailed topographical, rheological and hydrological data are not available, DAN-W, which requires less detailed data, is a valuable tool to predict debris-flow hazard. Parameters obtained through back-analysis with both models can be applied to predict hazard in other areas characterized by similar geology, morphology and climate.