贵州关岭大寨崩滑碎屑流灾害初步研究

2010年6月28日,贵州省关岭县岗乌镇大寨村发生特大型崩滑碎屑(石)流灾害,造成99人死亡或失踪。通过现场考察崩滑区的地质环境与斜坡岩体结构,认为斜坡体由似"干砌块石结构"的裂隙化岩体组成是发生崩溃式破坏的主要内在原因。超常暴雨(过程雨量237mm)条件下斜坡岩体后缘裂缝充水形成持续的"水楔作用"是斜坡岩体松动、倾倒垮塌的主要外部引发因素。碎屑(石)流块度的空间分布具有从源头向沟口逐次减小,碎屑(石)流运动冲击高度逐步降低,冲击速度逐步减小,并显示4个能级4个冲程的特点。根据动势能守恒定律,计算了每个冲程的最大速度,得出第1冲程为高速崩滑,其它冲程属于碎屑(石)流动冲击。未发现区域天然地震、光照水库诱发地震与外围历史采矿活动与本次事件相关的直接证据。由于滑坡后缘仍存在不稳定岩体,碎屑(石)流堆积体上多处分布直径3～5m的堰塞塘,说明碎屑(石)空隙的排泄能力不足,在未来暴雨条件下引发新的崩滑或形成沟谷型泥石流的可能性是存在的。     

Anomalous Alpine fans: from the genesis to the present hazard

The present paper aims at characterising Alpine anomalous basin-fan systems, in order to develop a method for hazard assessment for such fans. The review of previous studies revealed that anomalous basin-fan systems are often associated with deep-seated slope failure and present-day hazard is associated to debris flow occurrence. Taking into account these peculiarities, a modelling approach to assess the present day hazard in anomalous fans has been developed and applied to the Sernio fan (Valtellina, northern Italy). Debris flow inundation areas have been simulated by means of a numerical model (RApid Mass MovementS (RAMMS) debris flow), which includes a routine for the sediment entrainment. The range of the model parameters was defined based on previous studies, enabling a sensitivity analysis on the debris flow runout, as well as the flow height and velocity. Numerical results point out the paramount importance of entrainment phenomena on debris flow dynamic in anomalous systems, especially with reference to the bulking factor and debris yield rate that reach very high values, typical of basins with unlimited solid supply.     

Dating of multi-period earthquake-triggered rockfalls: a method for revealing paleo-seismic events that occurred along the Yushu fault in the eastern Tibetan Plateau

Landslides - The quantitative study of earthquake-triggered rockfall debris along seismogenic fault zones has proven to be a valid approach for use in identifying paleo-earthquakes and faulting...     

西藏天摩沟泥石流形成机制与成灾特征

西藏林芝市波密县天摩沟于2007年9月、2010年7月、2010年9月和2018年7月分别发生大型和巨型泥石流,4次泥石流活动均不同程度堵塞主河帕隆藏布,淤埋国道318或摧毁桥梁,堰塞湖淹没村道、溃决造成下游塌岸,给当地居民生命财产尤其是交通干道造成极大危害。文章针对以上4次泥石流活动,采用高分辨率遥感影像,对泥石流发生前的孕灾背景进行解译,同时结合无人机航空摄影和地面调查对天摩沟泥石流形成机制和成灾特征进行了对比分析,得到以下结论:(1)天摩沟内冰川发育,年际变化大,目前泥石流形成的主要方式为岩崩和堵溃,其中2018年和2007年为岩崩引发,2010年为堵溃引发,该沟同时具有冰川泥石流和降雨泥石流的特征。(2)经历了2007年和2010年3次大规模泥石流后,天摩沟内斜坡类物源储量增加了19.6%,绝大部分启动的冰碛物和崩滑物源都转化为泥石流沟道堆积物或冲出沟口。(3)天摩沟2018年泥石流容重为2.10g/cm^3,为黏性泥石流,流速快冲击力强,帕隆藏布河道受到挤压多次变道,历史上最大偏移距离为190m。(4)2018年7月11日泥石流成因为降雨条件下加剧冰川消融引发主沟沟源右侧岩崩,形成多阵次泥石流,主泥石流体积18×104m3,淤埋G318近220m。后续依然具有暴发大型泥石流的可能性,建议进行防治降低其危害程度。     

ROckfall risk MAnagement assessment: the RO.MA. approach

The analysis of risk for vehicles and drivers as a result of rockfall on a road is relevant to design management in geotechnical engineering. This process is very complex due to the large number of parameters involved. In this paper, we discuss risk analysis and management procedures for roads subject to rockfall phenomena. To this aims, we are proposing a quantitative method (the RO.MA. approach). We developed an abacus to define the threshold values of acceptable rockfall risk for a given road. Rockfall risk is calculated using an Event Tree approach and compared with the abacus thresholds to evaluate road safety and the need for additional protective measures to reduce the risk to an acceptable level. The approach was successfully applied at a test site located in Bard, Aosta Valley, north-western Italy.     

泥石流危险性分区及其在泥石流减灾中的应用

泥石流是一种突发性山地灾害,至今尚缺乏准确有效的预报方法。减灾工程也只能对一定规模的泥石流起到防御作用。泥石流危险性分区在泥石流减灾中具有重要作用。以泥石流运动数值模拟为基础,以数值模拟获得的流速和流深等参量为分区指标的危险性分区是泥石流危险性分区研究的重点和发展方向。其中,泥石流危险性动量和动能分区充分反映了泥石流的破坏能力,可以提供更为精确的定量化的分区结果。该类分区方法在城镇等有重要危害对象的泥石流减灾中具有广泛的应用。不仅可以应用于泥石流危险区和安全区的划定、泥石流灾害预估、泥石流临灾预案制定、泥石流抢险救灾方案制定和泥石流灾情评估等,还可以应用到山区土地利用规划、山区城镇建设规划和财产保险评估等领域,并起到防灾和减灾的作用。     

Recent colluvial sedimentation in Jordan: fans evolving into sand ramps

Abstract High‐angle accumulations of sand and escarpment‐derived gravel along the outcrop walls of Plio‐Pleistocene sandstones, eastern Jordan, form small, coalesced colluvial fans, built by rockfalls, rockfall‐derived debris flows, dry sandfalls and sandy grainflows. These deposits are sourced through wind erosion of fault‐controlled outcrops of weakly cemented sandstone and a hard, gypsum‐cemented sandstone and fine conglomerate caprock exposed in sandpits. Eroded sediment is supplied to the fans directly as rockfalls and sandfalls, and indirectly as gully‐confined sandy grainflows. The preserved colluvium fans comprise sandy, matrix‐rich rockfall, rockfall‐derived, dry debris‐flow lenticular gravel deposits and minor lenticular sandy grainflow deposits. The fans develop initially against the footwall escarpment and, as erosion continues, the outcrop and the fans become covered by stable sand sheet ramps in a self‐regulatory geomorphic system. Preserved fan–sand ramp systems in eastern Jordan are characterized by a threefold hierarchy of genetically related bounding surfaces, which develop over short time scales. Rapid fault‐controlled uplift and/or rapid stream incision may produce non‐equilibrium scarp faces, identical to those in the sandpits, associated with the colluvial fan–sand ramp systems. Thus, such systems have the potential to identify fault‐related unconformities, rapid uplift events and episodes of rapid downcutting in the rock record. Colluvium deposits have good preservation potential, but are often associated with complex, coarse, basin‐margin facies, and are thus difficult to identify in the stratigraphic record; a problem exacerbated by the lack of adequate colluvium facies models and diagnostic sedimentary criteria.     

三门峡市地质灾害发育特征与防治对策研究

文章着重论述了三门块市地震、地面变形、崩塌、滑坡、泥石流、土壤侵蚀、地方病等主要地质灾害发育现状；分析它们发生和发展的地质环境背景。包括自然地理、地质地貌、构造、水文地质、工程地质条件，并对人类经济活动引起的崩塌、滑坡、泥石流、土壤侵蚀发展趋势、地面变形等问题进行了预测。在此基础上，提出了对主要地质灾害采取的防治对策和建议。     

新型悬挑式泥石流网格格栅坝及其应用

悬挑式网格格栅坝是从工程实践中在传统网格格栅坝的基础上演变而来的一种新型的格栅坝体类型,该种坝型继承了网格格栅坝的各种优点,并且通过悬挑格栅的独特设计,更具突出在非排导泥石流时对河流沟谷地的常态水流进行非拦截性排流,使河流沟谷内常态水流更为通畅,不会干扰河流沟谷的正常流通,是传统网格格栅坝的优化坝型,均适用刚性和柔性网格材料筑坝。目前国内还没有该种坝型的研究成果和相关技术资料,文章通过阐述其在以水流为主的稀性泥石流和挟带大量推移质的高含沙洪水的泥石流治理工程中的应用研究,得出该坝型的优缺点和相关技术成果,作为进一步工程实践和研究提供基础技术依据,从而进行悬挑式网格格栅坝在泥石流防治工作中的应用和推广。     

Influence of particle size on the buffering efficiency of soil cushion layer against rockfall impact

Natural Hazards - Soil cushion layers are commonly paved in front of protection structures to avoid the direct impact of rockfall and debris flow. This study is devoted to investigating the...     

西藏墨脱公路工程地质灾害遥感勘察与解译方法

在地处南迦巴瓦峰地区的西藏墨脱公路工程地质遥感勘察中，以Landsat-7 ETM＋卫星影像为信息源，运用彩色合成、数据融合、主成分分析等数字图像处理方法，结合基于地学知识的图像识别及解译技术，对墨脱公路沿线的泥石流、滑坡、活动断裂等地质灾害进行全面解译分析及专题制图，查明了公路方案线区域内活动断裂发育特征。其中，帕隆藏布断裂带、岗日嘎布断裂带等对错拉隧道将产生较大影响。大型滑坡主要有5个，沿南迦巴瓦峰南坡的雅鲁藏布江河谷两岸发育，分布在仓孔、墨脱及洒拉库等地。泥石流、崩塌广泛发育，主要分布在雅鲁藏布江河谷、帕隆藏布河谷沿线的派、拉格-汗密、岗乡-波密一带。勘察及解译结果为墨脱公路工程线路方案选择、工程地质条件评价提供了充分的科学依据。     

西藏波密—林芝环境地质灾害及防治

本文在利用遥感技术和野外实地调查的基础上,研究了波密—林芝环境地质形成的主要控制因素,认为印度板块和欧亚板块碰撞形成的东部构造结及其所形成的活动断裂系统控制了研究区的地形地貌发育、水文气候和植被,进而控制洪涝、岩崩、泥石流、滑坡和崩塌,以及地震等灾害,并提出防治建议。     

Overturning stability of L-shaped rigid barriers subjected to rockfall impacts

Reinforced concrete barriers are commonly used as defence measures in hilly areas to contain falling boulders and landslide debris. These barriers are conventionally designed to satisfy the conditions of force and momentum equilibrium with a factor of safety. A major limitation of this approach is that the inertial resistance of the barrier is neglected such that the design could be over-conservative. This paper presents a novel displacement-based approach for the assessment of overturning stability of rigid L-shaped barriers subjected to rockfall impacts. Analytical solutions, which are derived based on conservation of momentum and energy, are used to take into account the contributions of the self-weight and, thus, the inertial resistance of the barrier in resisting an impact. The actual amount of energy transferred from the impacting boulder to the barrier is considered by including the coefficient of restitution between the two objects. The accuracy of the analytical solutions has been confirmed by laboratory impact experiments. Numerical assessments conducted using the new solutions indicate that a reasonably sized rigid barrier, due to its own inertial resistance, may adequately withstand the impact action of a heavy boulder rolling down a hillslope without relying on any anchorage to its support. A range of geometric design of the barriers with L-shaped cross sections also has been considered and analysed. The new approach presented in this paper is easy to apply in practice and will be useful for engineers designing concrete barriers as passive rockfall mitigation measures.     

Seismic-induced rockfalls and landslide dam following the October 30, 2016 earthquake in Central Italy

On October 30, 2016, a seismic event and its aftershocks produced diffuse landslides along the SP 209 road in the Nera River Gorge (Central Italy). Due to the steep slopes and the outcropping of highly fractured and bedded limestone, several rockfalls were triggered, of which the main event occurred on the slope of Mount Sasso Pizzuto. The seismic shock acted on a rock wedge that, after an initial slide, developed into a rockfall. The debris accumulation blocked the SP 209 road and dammed the Nera River, forming a small lake. The river discharge was around 3.6 m³/s; the water overtopped the dam and flooded the road. By a preliminary topographic survey, we estimated that the debris accumulation covers an area of about 16,500 m², while the volume is around 70,000 m³. The maximum volume occupied by the pre-existing talus mobilized by the rockfall is about 20% of the total volume. Besides blocking the road, the rockfall damaged a bridge severely, while, downstream of the dam, the water flow caused erosion of a road embankment. A rockfall protection gallery, a few hundred meters downstream of the dam, was damaged during the event. Other elastic nets and rigid barriers were not sufficient to protect the road from single-block rockfalls, with volumes around 1–2 m³. Considering the geological and geomorphological conditions, as well as the high seismicity and the socioeconomic importance of the area, a review of the entire rockfall protection systems is required to ensure protection of critical infrastructure and local communities.     

Numerical Simulation in Rockfall Analysis: A Close Comparison of 2-D and 3-D DDA

Accurate estimation of rockfall trajectory and motion behaviors is essential for rockfall risk assessment and the design and performance evaluation of preventive structures. Numerical simulation using discontinuous deformation analysis (DDA) is effective and helpful in rockfall analysis. Up to now, there have been many reports on application of two-dimensional (2-D) DDA programs. In this paper, the major advantages of rockfall analysis using 2-D and extensions to three-dimensional (3-D) analysis are presented. A practical 3-D DDA code is demonstrated to be capable of simulating free falling, rolling, sliding, and bouncing with high accuracy. Because rockfall trajectories and motion behaviors can be described as combinations of these four types, this demonstration indicates that the implemented code is capable of providing reliable rockfall analysis. Finally, specific tests are conducted to compare 2-D and 3-D DDA rockfall analysis in predicting trajectory and dynamic behavior. The results indicate that 3-D DDA simulations are more appropriate for rough tree-laden inclined slopes in providing detailed spatial distribution, whereas 2-D DDA simulations have better efficiency for slopes dominated by valleys and ravines. These results can help in selecting the appropriate DDA simulation for rockfall analysis.     

Reliability-based design and its complementary role to Eurocode 7 design approach

Reliability-based design (RBD) can play a useful complementary role to overcome some limitations in the Eurocode 7 (EC7) design approach, for example in situations with parameters not covered in EC7, different parametric sensitivities across different problems, cross-correlated or spatially correlated parameters, design aiming at a target reliability or failure probability, or when uncertainty in unit weight of soil is modeled. The complementary role played by RBD under these circumstances is illustrated and discussed for a shallow foundation, a reinforced rock slope, a Norwegian clay slope with spatial variability, a laterally loaded pile requiring implicit numerical analysis, and an anchored sheet pile wall. A pragmatic RBD approach involving first-order reliability method (FORM) only and a more rigorous RBD approach involving both first-order and second-order reliability method (SORM) are offered. Both approaches are implementable using either spreadsheet-based FORM and SORM procedures, or using various commercially available FORM/SORM packages.     

冰雪型地质灾害链高位萌生、动力溃散及物相转化过程剖析北大核心CSCD

受全球气候变暖对高海拔山地区气温放大效应影响,冰雪型地质灾害趋于增多,且普遍呈现链式发育特征,具有灾害类型动态转化、影响范围大、破坏程度高等特点,严重威胁区域内重大工程建设安全。基于实地考察与文献调研方式,将高寒山地区常见冰雪型地质灾害凝练为:冰岩崩、雪岩崩、冰雪型碎屑流、冰碛物堆积滑坡、冰湖溃决、冰川型泥石流6类,并分别剖析各自典型的发育特征;而后,对冰雪型地质灾害3种典型链式组合关系予以剖析,发现:冰雪型地质灾害链普遍存在“高位萌生→动力溃散→物相转化”动态演化过程;据此,对冰雪型地质灾害高位萌生、动力溃散及物相转化三阶段特征及内在机制进行分析,明确了冰雪型地质灾害的“高位萌生→位能转化→侵蚀铲刮→滑移堆积”累积链生放大机理。最后,对冰雪型地质灾害链各演化阶段进行评价模型梳理,认为:新型破碎-扩散模型、Flores接触力模型可用于评价冰雪型地质灾害高位萌生向动力溃散过程;犁切模型可较好描述其侵蚀铲刮与体积放大过程;颗粒流模型、空气润滑模型、超孔隙水压力模型可用于揭示后续的高速滑移堆积特征;而Voellmy流变模型、Bingham流体渗流模型可较好解释其灾害链条的物相转化特征。研究对于科学评价冰雪型地质灾害链动态演化过程具有基础参考价值。     

Load-resistance duality and case-specific sensitivity in reliability-based design

Acta Geotechnica - Reliability-based design (RBD) can overcome some limitations and ambiguities in the partial factor design approach found in Eurocode 7 (EC7) and the load and resistance factor...     

新疆的干旱环境与滑坡,泥石流及其防治对策

新疆的干旱气候环境,导致荒漠广布.受温差悬殊制约,风化作用强烈.不论山地或平原,松散物均较发育,由于降水时空分布不均,崩,滑,流具有明显的时空分布特征,大雨、暴雨往往集中在夏季。暴雨洪流,融雪洪流成了引发泥石流的动力。特殊的内陆环境条件,决定新疆降水量有限。受水动力条件不足制约,新疆的滑坡多系小型土滑,且往往与泥石流共生。换句话说,滑坡为泥石流提供了物源。因此,对新疆滑坡,泥石流的治理,应本着近期治标,长期治本的原则,以土木系统工程治表、生物系统工程治本。与此同时,还要强调社会系统工程,作为实施各项防护举措的保证。通过综合治理,以促进改善生态环境。     

Characteristics and remediation of a landslide complex triggered by the 2008 Wenchuan, China earthquake-case from Yingxiu near the earthquake epicenter

During the 2008 Wenchuan earthquake, the river valley from Yingxiu to Wenchuan experienced numerous landslides and became a prominent area of landslide complexes. The present large landslide complex near the earthquake epicenter consisted of Laohuzui slide 1, Laohuzui slide 2 and Douyaping slide. The scale, geology, morphology, sliding process, and failure mechanism of the landslide complex are analyzed by means of field investigation, aerial photograph and stereographic projection technique. Characteristics of these three slides including seismic response of slope, landslide debris, damage and potential failure are discussed: the convex slope and the upslope of fractured granitic rock at high altitude are highly prone to landsliding under earthquake; the high source altitude and long travel path determine grain sizes and the deposit angle of the slide debris; the landslide complex completely buries the G213 roadway and dams up the Minjiang River in these sections; after the earthquake, rainfall, aftershocks and river erosion may retrigger new failures, such as retrogressive slide of weathered fractured rock, colluvial landslide, debris flow, embankment failure and rockfall. The following are presented as suggested remedial measures to protect the roadway and stabilize the slope: the removing and trenching, protective concrete/rock blocks against erosion, retaining structure, rockfall stopping wall, rockfall restraining net, rock bolt, and the planting of vegetation.