Analysis of debris flow control effect and hazard assessment in Xinqiao Gully,Wenchuan M_(s)8.0 earthquake area based on numerical simulation

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 by41.05%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.

Mitigation measures of debris flow and landslide risk carried out in two mountain areas of North-Eastern Italy

The design of remediation works for the mitigation and prevention of the associated risk is needed where these geological hazards affect anthropized areas. Remedial measures for landslides commonly include slope reshaping, plumbing, drainage, retaining structures and internal slope reinforcement, while debris flow control works consist in open or closed control structures. The effectiveness of the remedial works implemented must be assessed by evaluating the reduction of the risk over time. The choice of the most appropriate and cost-effective intervention must consider the type of hazard and environmental issues, and selects, wherever possible, naturalistic engineering operations that are consequently implemented according to the environmental regulations or the design and specification standards imposed by the competent public administrations. The mitigation procedures consist of five basic steps:(a) acquisition of the knowledge of the hazard process;(b) risk assessment with identification of possible disaster scenarios;(c) planning and designing of specific remedial measures to reduce and/or eliminate the potential risk;(d) slope monitoring after application of remedial measures,(e) transfer of knowledge to the stakeholders. This paper presents two case studies describing the practice for the design of the mitigation measures adopted for debris flow and active landslide sites in North-Eastern Italy. The first case study is a debris flow site, for which, based on observation of past events and numerical simulations using the software FLOW-2D, the most suitable mitigation measures were found to be the construction of a debris basin, barriers and breakers. The second case study deals with an active landslide threatening a village. Based on the landslide kinematics and the results of numerical simulations performed with the code FLAC, hard engineering remedial works were planned to reduce the driving forces with benching and by increasing the available resisting forces using jet grout piles and deep drainage.

The formation of the Wulipo landslide and the resulting debris flow in Dujiangyan City, China

The Wulipo landslide, triggered by heavy rainfall on July 10, 2013, transformed into debris flow,resulted in the destruction of 12 houses, 44 deaths, and 117 missing. Our systematic investigation has led to the following results and to a new understanding about the formation and evolution process of this hazard. The fundamental factors of the formation of the landslide are a high-steep free surface at the front of the slide mass and the sandstone-mudstone mixed stratum structure of the slope. The inducing factor of the landslide is hydrostatic and hydrodynamic pressure change caused by heavy continuous rainfall. The geological mechanical model of the landslide can be summarized as "instability-translational slide-tension fracture-collapse" and the formation mechanism as "translational landslide induced by heavy rainfall". The total volume of the landslide is 124.6×104 m3, and 16.3% of the sliding mass was dropped down from the cliff and transformed into debris flow during the sliding process, which enlarged 46.7% of the original sliding deposit area. The final accumulation area is found to be 9.2×104 m2. The hazard is a typical example of a disaster chain involving landslide and its induced debris flow. The concealment and disaster chain effect is the main reason for the heavy damage. In future risk assessment, it is suggested to enhance the research onpotential landslide identification for weakly intercalated slopes. By considering the influence of the behaviors of landslide-induced debris flow, the disaster area could be determined more reasonably.

Debris flow and landslide hazard mapping and risk analysis in China

This paper assesses the hazardousness, vulnerability and risk of debris flow and landslide in China and compiles maps with a scale of 1：6000000, based on Geographical Information System （GIS） technology, hazard regionalization map, socioeconomic data from 2000. Integrated hazardousness of debris flow and landslide is equivalent to the sum of debris flow hazardousness and landslide hazardousness. Vulnerability is assessed by employing a simplified assessment model. Risk is calculated by the following formula： Risk = Hazardousness × Vulnerability. The analysis results of assessment of hazardousness, vulnerability and risk show that there are extremely high risk regions of 104 km2, high risk regions of 283008 km2, moderate risk regions of 3161815 km2, low risk regions of 3299604km2, and extremely low risk regions of 2681709 km2. Exploitation activities should be prohibited in extremely high risk and high risk regions and restricted in moderate risk regions. The present study on risk analysis of debris flow and landslide not only sheds new light on the future work in this direction but also provides a scientific basis for disaster prevention and mitigation policy making.

Assessment of Secondary Mountain Hazards along a Section of the Dujiangyan Wenchuan Highway

Conducting a hazard assessment for secondary mountain hazards is the technical basis for reconstructing destroyed highways and for disaster prevention.It is necessary to consider the role and influence of structural engineering measures as an important assessment factor.In this study,based on six substantial field investigations conducted between July 2008 and July 2012,a 2 km wide zone along both sides of the Dujiangyan Wenchuan(Du Wen) Highway was selected as the study area.Microgeomorphic units and small watersheds in the study area were extracted with GIS software and used as basic assessment units.Through field investigations,remote sensing surveys and experimental analysis,a structural engineering effectiveness assessment was conducted using the technique of principal component analysis.The results showed the following:1) A total of 491 collapses,12 landslides,32 slope debris flows and 17 gully debris flows were scatted across the study area.The total overall areal density of all mountain hazards was 25.7%.The distribution of secondary hazards was influenced mainly by seismic intensity,active fault zones,lithology,slope and altitude.More than 70% of secondary hazards occurred in zones with a seismic intensity of XI,a distance to the fault zone of between 0 and 25 km,a slope between 25° and 50°,and an altitude of between 1,000 m and 1,800 m.2) Different structural engineering measures play different roles and effects in controlling different types and scales of secondary mountain hazards.3) With a secondary mountain hazard area of 128.1 km2and an areal density of 34.9%,medium,high and very high hazard zones accounted for 74% of the study area and were located on the high,steep slopes along both sides of the highway.The low hazard zone was located mainly in the valley floor,on gentle slope platforms and at locations 1.5 km away from the highway the hazard area was 45 km2and the areal density was 3.3%.4) The methodology for hazard assessment of secondary mountain hazards,which is based on five factors,solves such key technical problems as the selection of assessment units,multi-source data fusion,and the weight calculation for each assessment index.This study provides a new and more effective method for assessing secondary mountain hazards along highways,and the proposed models fit well with validation data and field observations.The findings were applied to reconstruction and disaster mitigation in the case of the Du Wen Highway and proved to be feasible.

级配与拦挡位置对滑坡碎屑流运动影响研究

为了研究不同级配的高位滑坡碎屑流经多级偏转后冲击不同拦挡结构的运动特性以及致灾效应,结合自然地形构建固定坡度和偏转角度均为45°的离散元模型,并利用DEM软件进行数值模拟分析不同拦挡工况和不同级配对碎屑流颗粒运动过程中能量耗散、最终堆积形态,以及碎屑流冲击挡板的作用高度的影响,进而建立相关冲击力学模型。研究结果显示:(1)上下均设置挡板的工况能有效减缓碎屑流颗粒的平均动能和势能,且能有效降低颗粒流翻越挡板的数量,并降低颗粒流的最大运动距离从而减小致灾范围;随着颗粒组级配的增大,势能时程曲线分散点出现的时间越晚,颗粒流最终堆积面积中细颗粒组最大,粗颗粒组最小。(2)当滑槽底部反作用力位置取2/3静止堆积体长度时,计算所得碎屑流最大冲击作用高度与模拟试验结果相接近,力学模型计算的冲击作用高度在0.017~0.138 m。在实际工程中,可按研究相似比对此范围进行加强抗冲击防护。(3)由于侧板的切向力和“颗粒分选效应”,大颗粒会主要冲击挡板的中上部,小颗粒主要冲击挡板的下部,并受偏转角影响集中在一侧,因此工程设计可根据实际情况避免在沟道偏转方向的反向建设工程。研究结果可为高位滑坡碎屑流灾害的治理防护提供参考。

The Occurrence Mechanism of Geological Disasters and Countermeasures in a Certain Area

In recent years, natural disasters in China have occurred frequently, especially large disasters such as earthquakes, floods and droughts, which have posed a serious threat to local public safety. In addition, the geological environment of local mountainous areas in China is complex and diverse, and climate change is large. Considering the dynamic coupling effect of rainfall conditions to stimulate geological disasters, this paper takes dynamic risk assessment technology as the guide, constructs a dynamic risk early warning model of geological disasters, establishes a prototype system, realizes dynamic risk assessment and emergency early warning of geological disasters at the regional level, and provides feasible technical support for targeted emergency disaster prevention. At the same time, the investigation and evaluation, mechanism research and monitoring and early warning related to the comprehensive prevention and control of geological disasters are important tasks that cannot be ignored, an important link in the emergency response system for geological disasters, and a key stage process to guide scientific disaster prevention. On the basis of exploring the mechanism and catastrophic effect of rainfall to stimulate landslides and mudslides, we will carry out in-depth research on disaster prevention countermeasures such as systematic engineering disposal, monitoring and early warning.

滑坡-泥石流灾害链特征分析与风险评价——以川西石棉县马颈子沟为例

我国川西地区地形地貌和地质构造复杂,滑坡-泥石流灾害链易发育,灾害链中主要灾害向次要灾害逐级传递,促使灾害的风险性进一步增强。为研究滑坡-泥石流灾害链的特征与风险性,以四川马颈子沟滑坡-泥石流灾害链为典型研究对象,对该区域滑坡和泥石流分别进行风险度分析,并对区域滑坡-泥石流灾害链进行特征分析与风险评价。首先构建AHP模型对滑坡危险度进行分析,并应用易损性等级计算模型计算滑坡易损性;然后应用泥石流危险区指标来估算泥石流的危险度,并根据区域统计数据得出区域泥石流灾害损失脆弱性;最后根据多灾害风险理论公式,计算区域滑坡-泥石流灾害链风险度,并对灾害链进行风险评价。结果表明:马颈子沟滑坡-泥石流灾害链为中风险度地区,该研究结果与现场勘察结果一致,验证了基于多灾害风险理论的灾害链分析评价方法体系结合多种模型进行计算的可行性。通过分析马颈子沟灾害链风险度,为类似研究提供理论依据。

江苏省宜兴地区碎石土滑坡地质灾害特征及防治措施研究

针对江苏省宜兴地区典型碎石土滑坡地质灾害,开展了滑坡地质灾害特征分析和防治措施研究。结果表明,碎石土滑坡主要发育于宜兴南部山区山前缓坡地带,自然边坡坡度不大于15°;滑坡体具有上土下岩的二元结构特征,滑坡破坏模式为后退式渐进整体变形破坏的牵引式滑坡,表现为地形改造+降雨诱发;滑坡体轴向水平距离为改造后边坡前缘高差的10.0~12.0倍。采用坡面修整、抗滑桩、回填压脚、挡土墙和截排水沟等综合防治措施可有效消除滑坡地质灾害隐患,坡体水平位移、垂直位移收敛于定值,坡体稳定。

涪江源区韩家沟泥石流防治工程改进前后危险性分析

为了降低涪江源区左岸韩家沟泥石流的危害,文章采用遥感解译、野外调查、FLO-2D数值模拟等手段,查清了韩家沟泥石流特征及其防治现状,认为现有防治工程不能满足防灾需求,并据此提出改进的防治工程,对不同降雨频率下防治工程改进前后的泥石流危险性进行了研究,并分析改进防治工程的有效性。结果表明:韩家沟位于“8·8”九寨沟地震扰动区,震后泥石流物源丰富,导致每逢强降雨时泥石流频发。在10年一遇降雨频率下,丰河村及平松路均处于低危险区,现有防治工程可有效防治泥石流灾害;在50年一遇降雨频率下,丰河村处于泥石流高危险区,泥石流冲出排导槽,冲毁平松路,现有防治工程不能满足要求。采用多级拦挡坝、排导槽截弯取直等改进的防治工程后,可有效预防泥石流对沟口下方承灾体的损害,泥石流堆积方量减少50.2%,堆积面积减少86%,高危险区均位于排导槽内,治理效果显著。

新疆阜康抽水蓄能电站库区泥石流危险性评价与防治措施

根据新疆阜康抽蓄库区泥石流形成条件及发育特征,通过现场调查、遥感解译、现场试验等方法确定了影响较大的4条沟谷泥石流静力、动力特征值,选取泥石流多因子综合模型评价了泥石流的危险性,并从两方面分析了泥石流对工程安全的影响,提出了“稳坡、拦挡、停淤”的综合防治体系。结果表明:西岔沟泥石流危险度最大,值为0.43,属于中度危险;库区泥石流沟的影响主要表现为淤泥作用和冲击作用;“稳、拦、停”的立体综合防治体系具有良好的防治效果,值得推广采用。

川西北某泥石流沟发育特征及易发性评价

川西北某泥石流沟位于汶川“5.12”8级地震中心影响区域岷江河谷,该区域地质构造复杂,新构造运动强烈,强震频发,加之受岷江河谷深切,地形陡峻,出露地层以软质岩为主,沟道及两侧物源十分丰富,强降雨条件下易引发泥石流灾害。通过收集区域地质资料、遥感解译、现场地质勘察和力学计算等方法相结合,从地形、物源和水动力条件等方面,研究了该区域某泥石流沟的发育特征并开展易发性评价,提出了相应的工程防治对策。研究结果表明:(1)川西北某泥石流沟为暴雨崩滑沟谷型泥石流,泥石流沟流域面积20.8 km^(2),固体物质总储量约258.9×10^(4) m^(3),可能的动储量约64.5×10^(4) m^(3);(2)100年一遇的泥石流重度为1.74 t/m^(3),平均流速为5.12 m/s,最大峰值流量为535.4 m^(3)/s,泥石流最大冲起高度为1.34 m,预测100年一遇的泥石流淤积厚度为4.8 m,具有中度易发性风险;(3)针对工程区的泥石流发育特征及易发性程度,建议以桥梁工程形式并留足净空通过泥石流沟,提出了泥石流防治对策与建议。研究成果对川西北山区铁路勘察设计和施工建设具有一定借鉴价值。

北天山干线泥石流发育特征与防治措施研究

北天山干线穿越多种地貌类型、地质构造复杂、灾害种类及数量均偏多,制约着新疆地区公路、铁路等基础建设的发展。以北天山G577线精河至伊宁县公路沿线泥石流为研究对象,对泥石流的发育特征、防治措施、选线及通过形式进行系统研究,提出北天山干线泥石流避让方式及防治措施。

基于EW-AHP改良未确知测度理论的泥石流危险性评价方法

针对泥石流危险性评价中确定指标权重过度主观的缺陷,以甘肃省陇南市武都区两水村大湾沟泥石流为例,根据其地质环境特征,选取一次泥石流最大冲出量、流域面积、主沟长度、流域相对高差、泥沙补给段长度比、24 h最大降雨量、人口密度共7个因子作为泥石流危险性评价指标,引入熵权和层次分析法(EW-AHP)组合赋权确定指标权重,建立基于未确知测度理论的单钩泥石流危险性评价模型。对研究区泥石流危险性评价结果表明:结合评价指标的主、客观赋权,本评价模型的评价结果较符合现场调查结论,说明评价方法合理有效,可为今后泥石流危险性评价提供一种新途径。

贵平煤矿地质灾害研究及防治

随着煤矿开采的不断深入,所引起的地质灾害越发严重,特别是在开采多煤层时,地质灾害影响更为严重。为加强对山体滑坡、陡岩崩塌、泥石流、地面塌陷、地裂缝等地质灾害的防治,改善煤矿地质环境,根据矿井实际情况,结合各类地质灾害发生的特点,采取对采空区进行地表下沉量预测、无人机遥感监测等有效的防治措施,实现对风险的有效预防与控制,并加强地质灾害治理,保护煤矿地质生态环境,实现矿井长期安全稳定发展。

丰沙铁路山区段坡面型泥石流特征分析及防治建议

既有山区铁路泥石流灾害时有发生,随着极端气候变化灾害愈发严重,极大危及铁路行车安全,尤其以坡面型泥石流的高速度、大冲击力、突发性、短暂性等特征对铁路的影响较大,严重威胁行车安全。针对山区铁路发生坡面型泥石流的水害处所,通过现场踏勘并采用遥感影像及无人机倾斜摄影技术,对水害点展开调查研究,分析坡面型泥石流特征及发生机理,并提出针对性防治措施。研究结果可为类似水害治理提供参考。

滑坡-泥石流转化研究进展

近年来,随着山区工程建设日益活跃,由滑坡转化为泥石流所导致的巨型远程沟谷灾害,因其超强的运动性和巨大的破坏性而引起广泛关注。与单灾种滑坡相比,转化后的泥石流灾害规模更大、运动距离更远、流动性更强、危害程度更严重。科学的认识滑坡-泥石流转化过程,对从起始环节降低远程沟谷灾害风险,进而采取针对性减灾措施具有重要意义。本文基于现阶段国内外研究成果,系统综述了滑坡-泥石流灾害转化的概念、转化条件和转化机理。首先,对比高速远程滑坡-碎屑流,明确了滑坡-泥石流转化的概念。随后,从物源、水源和地形3个角度梳理了滑坡-泥石流转化的宏观条件,进一步梳理了现阶段用于划分滑坡、泥石流的静态、动态指标和方法。基于典型滑坡-泥石流转化野外案例和模型实验,总结了滑坡-泥石流转化的两种模式:“静-动”转化和“动-动”转化,分别就不同转化模式所对应的孕灾条件和物理机制进行了探讨。最后,基于对现有成果的分析,提出了滑坡-泥石流转化研究所面临的3个关键科学问题,指出了滑坡-泥石流转化研究可借鉴的相关理论和方法,探讨了未来滑坡-泥石流转化过程及物理机制分析的研究方法。

甘肃岷县纳古呢沟滑坡-泥石流灾害链成灾机制及其演化

【研究目的】纳古呢沟位于甘肃省岷县茶埠镇耳阳沟流域,构造上处于临潭—宕昌断裂分支断裂带内,是一条小规模高频泥石流沟。流域内发育的滑坡使得流域产生特殊的滑坡-泥石流灾害链,该灾害链的成灾机制和演化过程是值得深入研究的问题。【研究方法】通过野外调查及遥感解译,结合室内试验等手段,厘清了纳古呢沟灾害发育特征,研究了滑坡-泥石流灾害链的成灾机制,剖析了该小流域内断裂活动下的滑坡-泥石流灾害链演化过程。【研究结果】研究结果表明:纳古呢沟内滑坡-泥石流灾害链表现为泥石流-滑坡-溃决型洪水泥石流往复发展的形式,断裂现今活动导致沟内松散物源及不稳定坡体的发育,奠定了灾害链形成的物质基础,高频短时强降雨或连阴雨激发泥石流多次发生,泥石流侧蚀沟谷坡脚使得坡体失稳形成滑坡,滑坡堵塞沟谷形成堰塞湖,溃坝后形成溃决型洪水泥石流。灾害链的演化过程表现为:泥石流初发冲蚀沟道阶段、坡体变形逐渐接近临界失稳阶段、滑坡体下滑堵塞沟道形成堰塞湖阶段、堰塞湖溃决形成溃决型洪水泥石流阶段、对岸坡脚侵蚀坡体失稳下滑阶段、泥石流-滑坡-溃决型洪水泥石流往复发展阶段。【结论】纳古呢沟内灾害链的形成,是现今断裂活动、短时集中降雨或连阴雨共同作用的结果。纳古呢流域内每年雨季泥石流的多次发生与滑坡的蠕滑变形,导致纳古呢沟泥石流-滑坡-溃决型洪水泥石流灾害链往复进行。

卡口地形段泥石流堵塞效应分析——以四川什邡桦头尖泥石流沟域为例

泥石流在流经卡口段沟道时常出现暂时堵塞现象,并伴随着流量放大效应。文章通过典型卡口段泥石流野外调查和室内水槽试验,研究卡口段泥石流堵塞效应的影响因素与成因机制。研究显示:卡口段泥石流堵塞效应引起的流量放大或因松散固体物源堆积而产生的流量衰减,均与卡口部位的几何条件、泥石流流体、沟域特征、是否存在附加松散物源有关。单纯卡口的存在多为泥石流流量衰减的正面因素,而是否有松散物源的加入则是卡口段泥石流的堵塞效应发生的关键因素。此研究对认识泥石流在微地貌突变动、堆积规律,完善泥石流防治技术规程方面都具有重要的理论意义和应用前景。

中巴经济走廊地质灾害研究进展与展望

中巴经济走廊(CPEC)是连接中国与南亚、西亚的重要通道.CPEC北部大部为青藏高原、帕米尔高原山区,具有独特复杂的地质结构、活跃的构造运动、多样的地形地貌、多变的环境气候背景.CPEC内滑坡、泥石流及冰川跃动等相关灾害多发,影响着CPEC的安全建设和运营,面临巨大风险和挑战,地质灾害亦给当地社会和人民带来巨大损失.本研究系统总结了CPEC滑坡、泥石流及冰川相关灾害识别编目及成因、地质灾害评价、灾害防治与减轻等方面研究现状.针对当前研究存在的5点不足:孕灾背景研究较为薄弱、灾害早期识别有待进一步加强、灾害特征与机制揭示不够深入、灾害评价及方法有待发展、地质灾害综合防治有待提升等,提出相应建议.提出三方面展望:开展CPEC环境地质普查、地质灾害详查,建立完备的地质灾害本底数据;促进建立适于CPEC的地质灾害空天地联合监测识别技术体系,促进卫星数据共享体系升级;开展系统全面的地质灾害防治、风险评价、减灾与灾后恢复研究等.