Structure and composition of debris flows in the Eastern Sayan

Based on the catastrophic June 28, 2014, Arshan debris flows in the Eastern Sayan Mountains, the structure and lithological composition of the debris are studied and a debris flow defense system is proposed. Among five debris flows in this region, two flows 4.1 and 5.6 km long are scrutinized. The grain size and mineral composition of fans and mudflows, as well as their evolution scenario are studied. The paper also examines the engineering-geological features of debris flow sediments and their textural-structural and physical alterations in the course of settling. Specific attention is devoted to the lithological and climatic constraints of debris flows. It is noted that sediments of recent mudflows are characterized by a high underconsolidation and deliquescence, promoting the formation of high-plastic and fluidal zones that can migrate actively. The approach proposed for debris flow defense measures lies in the construction of flow diversion dams designed for orienting the debris flows toward the “debris dump site.”     

A prediction model for debris flows triggered by a runoff-induced mechanism

Many debris flows were triggered within and also outside the Dayi area of the Guizhou Province, China, during a rainstorm in 2011. High-intensity short-duration rainfall was the main triggering factor for these gully-type debris flows which are probably triggered by a runoff-induced mechanism. A revised prediction model was introduced for this kind of gully-type debris flows with factors related to topography, geology, and hydrology (rainfall) and applied to the Wangmo River catchment. Regarding the geological factor, the “soft lithology” and “loose sediments” in the channel were added to the list of the average firmness coefficient for the lithology. Also, the chemical weathering was taken into account for the revised geological factor. Concerning the hydrological factor, a coefficient of variation of rainfall was introduced for the normalization of the rainfall factor. The prediction model for debris flows proposed in this paper delivered three classes of the probability of debris flow occurrence. The model was successfully validated in debris flow gullies with the same initiation mechanism in other areas of southwest China. The generic character of the model is explained by the fact that its factors are partly based on the initiation mechanisms and not only on the statistical analyses of a unique variety of local factors. The research provides a new way to predict the occurrence of debris flows initiated by a runoff-induced mechanism.     

深海相中的砂质碎屑流沉积--以西藏特提斯喜马拉雅侏罗-白垩系为例

阐述了砂质碎屑流沉积特征、研究现状及其与其他深海碎屑沉积的区别 ,认为西藏特提斯喜马拉雅上侏罗统 -下白垩统深海沉积背景下的块状砂岩具有砂质碎屑流沉积性质 ,指出深海相中的块状砂岩可以预测。     

鄂西地区南沱组地层沉积特征及成因分析

以沉积学，流体力学的基本原理为基础，运用沉积对比，粒度统计等方面对鄂西地区南沱组杂砾岩的成因机理进行了探讨，通过岩石类型，剖面层序，岩石的砾石表面特征、碎屑颗粒分布规律及沉积物构造研究后认为，南沱组杂砾岩并非冰碛砾岩，而属海缘盆地下水泥石流和浅海相沉积。     

东营盆地渐新世早期前三角洲缓坡区的泥石流砂质碎屑沉积

东营盆地渐新世沙河街组第三段中部前三角洲暗色泥岩中,有许多长条状透镜状砂质碎屑岩体。它们的岩性以具有大量内碎屑为显著特征;并且,在泥质薄层和泥质撕裂块内,具有流纹构造;在韵律组成上,表现出上部为刚性筏、下部为层流段沉积的基本的二分性结构。本文认为这些是泥石流(碎屑流)沉积物,与浊流沉积物具有不同的特点。文内还将湖盆中内碎屑泥石流细分为砂质泥石流、粉砂质泥石流、碳酸盐质泥石流和泥质泥石流,并按组构和岩性讨论了沉积物的韵律分段及其成因意义。     

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.     

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。     

湘南晚泥盆世佘田桥期碳酸盐碎屑流沉积

湘南地区佘田桥期碳酸盐重力流沉积十分发育。据近年来的研究,其类型很多,包括台缘滑塌沉积、滑动沉积、碎屑流沉积、颗粒流沉积和浊流沉积(关伊文等,1983;杨振强,1984;湖南地科所,1984;沈德麒等,1987;曾允孚等,1988)。近来笔者对该区的重力流沉积特征进行了比较深入的研究,而对其中的碳酸盐碎屑流沉积的研究尤为详细。     

桩基础在大型泥石流拦砂坝中的应用

"5.12"震后,震区泥石流处于高发期。拦砂坝是目前泥石流治理工程中主要的工程措施,新近泥石流堆积体上修建重力式拦砂坝对地基和基础要求较高。以魏家沟泥石流治理工程1#拦砂坝实例,分析桩基承台基础在泥石流治理工程中的应用,并为类似工程的治理提供参考。     

Quartz-grain surfaces of debris flow material in the marginal mountains of Tibet

Debris flow is a natural phenomenon which occurs on steep slopes of mountain regions. Very often morainic material and nonmorainic sediments, such as debris flow material, fluvial and other sediments, are mixed in the marginal mountain systems of the Tibetan Plateau. The study of quartz-grain surface features of debris flow has an important significance for differentiating between different origins of Quaternary sediments. Features of quartz-grain in debris flow will be described as below:

1. The predominant shapes of quartz grains are irregular.
2. The degree of roundness of grains is in general are angular to subangular in shape.
3. The textures of quartz-grains in debris flows are conchoidal fractures, parallel steps and mechanical V-marks. Parallel steps are especially abundant. Their presence is the most characteristic indicator of debris flow sand, aiding in the differentiation between debris flow and glacial sand.
4. Fresh cleavage planes are extremely flat.

     

渤中25-1油田沙三段重力流沉积模式及油气地质意义

运用最新重力流沉积理论,以钻井岩芯、地震资料为基础,系统研究了渤海海域渤中25-1油田沙三段重力流沉积特征、类型、岩相组合、砂体空间展布特征以及沉积模式。结果表明,研究区主要发育滑塌重力流、砂质碎屑流、浊流3种重力流沉积类型,并构成5种典型的岩相组合,包括湖相细粒沉积与滑塌重力流组合（MS）、砂质碎屑流与滑塌重力流组合（DS）、砂质碎屑流与浊流组合（DT）、浊流与砂质碎屑流组合（TD）、湖相细粒沉积与浊流组合（MT）。研究区重力流沉积具有"源-坡-断-流"联控的"滑塌-砂质碎屑流-浊流"沉积过程与发育模式,其中砂质碎屑流砂体呈舌状体分布,浊流砂体则具有朵状体形态特征。储层综合评价表明,砂质碎屑流砂体粒度粗、宽厚比小、泥质含量低、物性好,是优质的重力流储层类型。对不同重力流类型沉积特征、展布形态以及储层性质的精细研究,对深水优质砂岩储层的预测具有重要的指导意义。     

五台山西南麓“龙泉关群”地层、构造特征及有关问题的讨论

根据造山带地层学地层划分原则,“龙泉关群”可划分为两个性质截然不同的地层单元:其一是“龙泉关构造岩层”,为构造地层单元;其二是“跑泉厂变沉积岩组”,属经典地层单元。前者经历了至少两期变形、变质作用,保留着走向近SN和近EW两组矿物拉伸线理以及角闪岩相和角闪岩相→绿片岩相退变质特征;后者仅发育有一组走向近SN矿物拉伸线理和一期绿片岩相变质作用。这表明:(1)“龙泉关群”实际上包含着两个世代不同的地层单元,应予解体。其中,“龙泉关构造岩层”形成于晚太古代末期,属于“阜平古陆块”刚性基底一部分;“跑泉厂变沉积岩组”的地层层位相当于“五台群”,是“阜平古陆块”西北陆缘带沉积,时代归属早元古代早、中期。(2)“龙泉关群”不是由一个统一的应力场同时形成的一套构造岩,因而不应将其作为一个大型韧性剪切带。(3)“龙泉关群”构成五台碰撞造山带前陆地区的活化基底和活化盖层两个大地构造相。“龙泉关群”的解体及其地层时代的重新厘定支持“板峪口组应归属滹沱群一部分”和“铁堡运动即为五台运动”的看法。     

基于模糊数学法评价滇西保山地区麻榔河泥石流沟的危险性

通过野外实地调查云南省保山市怒江东岸麻榔河泥石流的发育特征,并对其洪积物进行光释光（OSL）测年,认为是一个年轻的泥石流沟,危险性较大。在此基础上,依据泥石流发生的影响因素具有复杂性和模糊性的特点,采用模糊数学法对其危险性进行综合评判。选取7个因子作为泥石流危险度评价的主要关联因子,评价结果与野外调查的实际情况相符,属于中度危险（Ⅲ）。同时指出了评价过程中的2个关键点:建立权重集和确定隶属度。建立权重集的方法采用“理想点”的距离之和极小化为目标来优化确定,隶属度利用半梯形分布模型原理设计隶属函数来实现。经过反复的实验计算,证实此方法可操作性强,结果更符合实际。     

Linking rainfall-induced landslides with predictions of debris flow runout distances

Rapid debris flows are among the most destructive natural hazards in steep mountainous terrains. Prediction of their path and impact hinges on knowledge of initiation location and the size and constitution of the released mass. To better link mass release initiation with debris flow paths and runout lengths, we propose to capitalize on a newly developed model for rainfall-induced landslide initiation (“Catchment-scale Hydro-mechanical Landslide Triggering” CHLT model, von Ruette et al. 2013) and couple it with simple estimates of debris flow runout distances and pathways. Landslide locations and volumes provided by the CHLT model are used as inputs to simulate debris flow runout distances with two empirical- and two physically-based models. The debris flow runout models were calibrated using two landslide inventories in the Swiss Alps obtained following a large rainfall event in 2005. We first fitted and tested the models for the “Prättigau” inventory, where detailed information on runout path was available, and then applied the models to landslides inventoried from a different catchment (“Napf”). The predicted debris flow runout distances (emanating from CHLT simulated landslide positions) were well in the range of observed values for the physically-based approaches. The empirical approaches tend to overestimate runout distances relative to observations. These preliminary results demonstrate the added value of linking shallow landslide triggering models with predictions of debris flow runout pathways for a range of soil states and triggering events, thus providing a more complete hazard assessment picture for debris flow exposure at the catchment scale.     

Flow behaviour of the submarine glacigenic debris flows on the Bear Island Trough Mouth Fan, western Barents Sea

Using 3·5 kHz high-resolution seismic data, gravity cores and side-scan sonar imagery, the flow behaviour of submarine, glacigenic debris flows on the Bear Island Trough Mouth Fan, western Barents Sea was studied. During their downslope movement, the sediments within the uppermost part of the debris flows (<3 m) are inferred to have been deformed as a result of the shear stress at the debris–water interface. Thus, the uppermost part of the flow did not move downslope as a rigid plug. If present, a rigid part of the flow was located at least some metres below the surface. At c . 1000 to at least 1600 m water depth, the debris flows eroded and probably incorporated substrate debris. Further downslope, the debris flows moved passively over substrate sediments. The hypothesis of hydroplaning of the debris flow front may explain why the debris flows moved across the lower fan without affecting the underlying sediments. Detailed morphological information from the surface of one of the debris flow deposits reveals arcuate ridges. These features were probably formed by flow surge. Hydroplaning of the debris flow front may also explain the formation of flow surge. The long runout distance of some of the large debris flows could be due to accretion of material to the base of the debris flow, thereby increasing in volume during flow, and/or to hydroplaning suppressing deceleration of the flow.     

贵州紫云羊场石炭—二叠纪之交的重力流沉积及其意义

<正> 贵州南部上石炭—下二叠统地层发育,沉积连续,各门类化石丰富,是石炭—二叠系界线地层研究的重点地区。各门类古生物由于生态的差异,通常不在一个剖面上共生,特别是和牙形刺在各剖面上成互为消长关系。在台地浅水区,相当丰富而牙形刺罕见;在盆地深水区,牙形刺丰富,但无原地生活的,所产的少量也为重力流带入;在水体较     

砂质碎屑流概念及其在鄂尔多斯盆地延长组深水沉积研究中的应用

砂质碎屑流是近年来日益受到重视的一种新的砂体成因类型,其相关理论是对"鲍玛序列"和"浊积扇"等深水沉积理论的部分否定和完善.阐述了砂质碎屑流概念精华与存在问题,指出只有进一步结合我国陆相盆地沉积不断完善该理论,才能提高勘探成功率,从而促进我国石油工业的发展.同时运用砂质碎屑概念,将鄂尔多斯盆地湖盆中心深水区延长组长6段...     

Residual luminescence in modern debris flow deposits from western Taiwan: A single grain approach

In an active fold-and-thrust belt, sediment is commonly transported in the form of debris and colluviums, and the ages of such deposits can be important for seismic hazard assessment. These sediments are mainly transported by high concentration flows that travel very short distances before burial, and therefore have very few opportunities for daylight exposure and bleaching, which limits the application of luminescence dating in such environments. Luminescence studies on modern debris flow deposits and channel sediments in central Taiwan indicate a mixed population of bleached and unbleached grains. The well bleached grains constitute a small proportion of the sediments and could only be identified using the single grain dating technique; doing single aliquot analysis may result in overestimation of the age of such sediments by 3–25 ka. The data reveal that outwash sediments are better bleached than debris flow sediments. Our results show that quartz that has experienced partial resetting can be used for luminescence dating only through the use of the single grain technique.     

Characteristics and temporal-spatial distribution of geohazards in western Sichuan

Xinqiao Gully is located in the area of the 2008 Wenchuan M_s 8.0 earthquake in Sichuan province, China. Based on the investigation of the 2023 “6-26” Xinqiao Gully debris flow event, this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards. Through field investigation and numerical simulation methods, the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event. The simulation results show that the debris flow control project reduced the flow intensity by 41.05% to 64.61%. The storage capacity of the dam decreases gradually from upstream to the mouth of the gully, thus effectively intercepting and controlling the debris flow. By evaluating the debris flow of different recurrence intervals, further measures are recommended for managing debris flow events.     

汶川县映秀镇红椿沟特大泥石流工程防治及初步效果分析

2010年8月14日,汶川县映秀镇强降雨导致红椿沟暴发特大泥石流灾害,冲出固体物质80.5104m3,泥石流堵塞岷江,导致河水改道冲入映秀镇,淤埋了沟口G213国道,毁坏了在建的映汶高速公路引桥路基及桥墩。据调查,在泥石流灾害发生前,沟域内即分布有大量的地震崩滑物源,沟道堵塞极其严重,在持续强降雨下极易发生泥石流。为预防再次暴发泥石流灾害,对红椿沟开展了详细调查,结果显示沟域尚有剩余物源量310.14104m3,其中动储量达98.4104m3,在强降雨条件下再次暴发大规模泥石流灾害可能性较大。本文在对红椿沟8 14特大泥石流暴发特征介绍基础上,分析了现状条件下泥石流的活动特征,并预测其发展趋势,最后结合泥石流沟工程治理设计思路及工程布置的作用,提出了全流域综合治理设计理念,即中、上游稳坡固源拦挡,下游固床+排导相结合的系统工程治理,通过稳源固坡、分级拦挡、分散淤积、调蓄消能、减势排导等系统的工程措施,达到控制灾害性泥石流发生的目的,确保映秀镇映秀新区、G213国道、映汶高速公路的安全。在工程竣工后的2011年7、8月两次强降雨时,红椿沟未有固体物质出沟进入岷江,治理工程效果得到了初步检验,体现了针对巨灾型泥石流沟采用全流域综合工程治理设计理念有较好效果。