Analysis of the Aso-Bridge landslide during the 2016 Kumamoto earthquakes in Japan

In 2016, earthquakes occurred beneath Kumamoto City, Kumamoto Prefecture in the Kyushu Region of Japan and generated numerous landslides around the city, and among those triggered in this disastrous event, the Aso-Bridge landslide was the largest. For the purpose of examining the behavior of this large-scale landslide during the main shock of the Kumamoto earthquakes, we conducted a study involving simplified sliding block concepts and finite element codes, and conclude that (a) the slope of the Aso-Bridge landslide (about 710 m high and with a dip angle of 33 °) is marginally stable in the absence of earthquakes; (b) the failure surface obtained using finite element codes is in satisfactory agreement with that of the actual failure surface; ©) our results reveal that the initiation-time of the Aso-Bridge landslide lay between 18.45 and 21 s based on three indications: (I) the directional tendency of the first apparent displacement, (ii) evidential factor of safety (FS) values <1, and (iii) Newmark’s displacement; and (d) the combination of an internal friction angle of 35 ° and a cohesion value of 80 kPa led to a failure surface closest to that observed in the field. The study demonstrates that we were able to apply the simplified sliding concepts and finite element codes to analyze the Aso-Bridge landslide in reasonable agreement with the actual event.     

Characterization of terrain surface and mechanisms of shallow landsliding in upper Kurokawa watershed,Mt Aso,western Japan

The paper describes the physical characteristics of the Mt Aso caldera (western Japan) where some 959 shallow landslides occurred between 1990 and 1998, denuding an area of 0.638 km². The variation in type and thickness of the recent pyroclastic deposits are described and linked to the spatial distribution of the landslides. The high monsoonal rainfall in July 1990 percolating into the recently deposited tephra overlying less permeable bedrock first saturated the soil mass and then effectively ‘floated’ the low density pyroclastic materials such that many slips occurred in the small, actively eroding, tributary valleys.      

Earthquake-triggered landslides by the 1718 Tongwei earthquake in Gansu Province,northwest China

The 1718 great Tongwei earthquake in northwest China caused more than 300 large-scale landslides near the epicenter resulting in more than 70,000 deaths. Although previous studies agree that the earthquake-induced landslides in the area are loess-landslides, which slid along ancient terrain surfaces, there is a dearth of evidence to unravel the actual failure mechanisms of these widely-documented events. To clarify their characteristics and mechanisms, the landslides in Pan’an Town, located in Gansu Province, China were rigorously investigated. The field surveys revealed that the landslides occurred in an area comprising loess deposits of several tens of meters underlain by a basal mudstone layer. It was also revealed that instability in the area is strongly influenced by a river valley with large erosion bank slopes, as well as steep mudstone slopes, which are well developed. The majority of the landslides triggered by the Tongwei earthquake were loess-mudstone composite landslides, with the sliding surface in the deep mudstone. Three huge landslides on the northern mountain located at the river bend of Pan’an Town with a total volume of about 6.06 × 10⁸ m³ are the main mass movements during the 1718 catastrophe. In addition, by taking the typical landslide named the Weijiawan landslide as a case study, the internal structure of the earthquake-triggered landslides and their stability were studied. The new findings not only aided the unraveling of the failure mechanisms but also provided insights and knowledge on early recognition of earthquake-triggered landslides in northwest China towns, especially in the surrounding valley, which shares similar geological conditions with landslides studied in this paper.     

Spatial patterns,controlling factors,and characteristics of landslides triggered by strike-slip faulting earthquakes: case study of Lefkada island,Greece

Bulletin of Engineering Geology and the Environment - The correlation of coseismic landslides with the seismic and morphological parameters has been investigated in detail by many researchers,...     

Studies on passive flexible protection to resist landslides caused by the May 12, 2008, Wenchuan earthquake

The landslides caused by the 5.12 Wenchuan earthquake resulted in enormous casualties and property losses. Since the earthquake, more than 3,600 landslides have occurred, and 17 of them were catastrophic, each of which has killed more than 30 people. Meanwhile, passive flexible protection has gradually been introduced to resist landslides due to its significant advantages of economy, safety, and environmental protection. To resist landslides effectively, it is necessary to study the load path and design method of passive flexible protection under the action of landslides. In the design of passive flexible protection against landslides, determination of the landslide load is the primary task. In this paper, the formulas of the probability density function and distribution function of the landslide pressure are developed to obtain the value of the accumulated landslide pressure acting on the passive flexible protection, which can be used as the load input parameter in the design of passive flexible protection to resist landslides. Based on the case of the “Shiziliang” potential landslide for the 5.12 earthquake, the pressure data of the landslide are collected, the calculation formulas of the volume, and the pressure of the intercepted landslide are established, and the statistical parameters of the landslide pressure‐loading sample are obtained. According to the Kolmogorov–Smirnov test method, the loading sample of the landslide pressure obeys an extreme‐value type‐I distribution, and then the load model of the landslide pressure is determined. Based on the reliability analysis method, the standard value of the landslide pressure with an over‐95% assurance rate is obtained. These results can provide references for load confirmation to design the passive flexible protection to resist landslides.     

Anatomy and behaviour of a post-eruptive rain lahar triggered by a typhoon on Mayon volcano,Philippines

Mayon Volcano in the Philippines, one the world's most active, is situated in a moist, tropical-maritime climate with frequent typhoons. A third of Mayon's eruptions generate destructive lahars (volcanic debris flows and hyperconcentrated streamflows). Lahars also occur during quiescent periods when monsoons and typhoons deliver rains of appropriate intensity and duration to the loose debris on the volcano slopes. Both eruption- and post-eruptive lahars occur most frequently during the typhoon-prone October–December season of the Northeast Monsoon. Post-eruptive lahars, the most poorly documented, are exemplified by a debris-flow event triggered by Saling, a typhoon of only moderate intensity, that occurred in Mabinit Channel on the southeast Mayon flank on October 17–18, 1985, one year after the last Mayon eruption. Detailed pre- and post-Saling surveys docment channel deepening of up to 4 m and maximum lateral erosion of 66 m. The debris flows left prominent, discontinuous multi-level terraces along the length of Mabinit Channel, either from pulsations due to temporary channel blockage, or as levee deposits. A significant volume of debris overtopped channel bends at 250–200 m elevations, coalescing to cover a 200,000 m² area of 4.5° slope with bouldery lateral deposits 1 m thick on the average. Channelized flows below this level plugged 0.5 km of the original channel and replaced it with a new conduit of comparable size. The Saling debris-flow deposits have a remarkably uniform sand-silt mode and less prominent, more variable modes in the pebble-boulder range. Shear strengths of the lateral flows ranged from 0.46×10⁴ to 2.32×10⁴ dn cm^?2; those of the channelized flows at the plug were significantly higher. Reconstructed flow velocity was 3.8 m sec^?1.     

Application of fuzzy logic in the preparation of hazard maps of landslides triggered by the twin Ahar-Varzeghan earthquakes (2012)

Bulletin of Engineering Geology and the Environment - The twin Ahar-Varzeghan earthquakes (Mw = 6.4 and Mw 6.2, August 12, 2012) are among the most severe and destructive seismic events to have...     

关于提高县区级开放大学效能的研究

提高开放大学效能是学校管理领域重要课题,对开放大学的内涵发展起着至关重要的作用,作为基层办学单位的县区级开放大学,提升管理效能显得尤为迫切。从构成开放大学效能的六大要素入手,本着提高县区级开放大学效能的方向性原则、创新原则、特色原则、适度超前原则、效能最大化原则、激励性原则等六大原则,梳理出提高县区级开放大学效能的六大基本要求。     

地层场地效应对东河口地震滑坡发生影响研究

以汶川极震区青川东河口地震滑坡为典型实例,首先从滑坡地脉动现场测试的频谱特征曲线分析可得,卓越频率在1~3Hz范围内,且NS向的谱比值最大。其次,通过对东河口滑坡单一结构、二元结构两种弹性模型输入不同中心频率0.5Hz~4Hz的Ricker子波,发现二元结构的PGA放大系数普遍大于单一结构,同时中心频率较低时,滑坡PGA放大系数分布范围较广,相反,较高中心频率的PGA放大系数仅集中在坡顶和两侧山脊处,表明：中心频率高低对于PGA放大系数影响范围也不同。最后,对东河口地震滑坡弹塑性模型输入汶川地震绵竹清平台站加速度记录,根据监测点残余变形,认为滑坡破坏发生在6.5s处,并结合输入地震波频率在此时刻出现较高傅立叶谱值,表明东河口地震滑坡的发生是由高频谱值输入地震波触发。本研究有助于从地层场地效应角度理解斜坡动力失稳过程。     

Performance analysis of Tohoku-Shinkansen viaducts affected by the 2011 Great East Japan earthquake

Tohoku-Shinkansen viaducts in eastern Japan were designed in accordance with specifications published in the 1970s. They have less shear reinforcement than required by current design specifications. Consequently, the No. 5 Inohana viaducts of Tohoku-Shinkansen failed in shear during the 2003 Sanriku-Minami earthquake. The viaducts were retrofitted by means of steel jacketing so that they had sufficient shear capacity. The retrofitted columns of the viaducts performed well during the 2011 Great East Japan earthquake. However, there is a lack of understanding of the impact of these retrofitting interventions on the vulnerability of the viaduct. It is important to recognise the relationship between the damage to the Shinkansen viaduct with retrofitted reinforced concrete columns and the ground motion intensity. After a brief review of the history of the performance of Shinkansen viaducts to several earthquakes prior to the 2011 Great East Japan earthquake, this paper presents fragility curves of the retrofitted and non-retrofitted Tohoku-Shinkansen viaducts based on nonlinear dynamic analyses and Monte Carlo simulation. It was found that the median of the fragility curve associated with the ultimate limit state for retrofitted viaduct is at least five times larger than that for as-built viaduct.     

东日本大地震灾害考察报告

日本的东日本大地震是近年来最大震级的地震,地震本身及造成的震害均具有很多特点。中日联合考察团将现场的考察及对有关问题研讨的主要内容写成本报告。对东日本大地震基本情况及主要特点,尤其是海啸的发生及范围、特征与严重程度作了重点介绍。地震灾害中由地震直接导致的建筑受害不严重,除介绍了震害总体状况,着重介绍了海啸造成的破坏状况及严重程度。除一般震况、震害外,报告中特别针对本次地震特点及国内关心的问题,重点说明了以下内容:长周期地震动的影响是本次地震的一个特点,介绍了其特性及造成的影响与有待研究的问题;日本减、隔震技术的发展现状以及在本次地震中的表现,同时对减、隔震建筑的发展中的问题作了说明;抗震加固工程在地震中的状况、经验与导向;对普遍关心的日本核电站的抗震设计,结合福岛核电站的事故作了介绍;经过本次地震之后,日本建设主管部门对建筑结构抗震初步考虑的对策。     

日本建筑抗震标准的变迁和现行的抗震标准

介绍了日本现行抗震标准及其修订背景。1924年世界上最早的建筑抗震标准在日本诞生,规定了至少取建筑物总重量的0.1倍的力作为设计水平地震荷载。日本现行抗震标准中的抗震设计由两次设计构成,即对在建筑使用年限中发生的中等地震进行第一次设计及对在建筑使用年限中可能发生的罕见大地震进行第二次设计。其现行抗震标准有四个基本的抗震设计方法。     

老挝万象省南坡金矿地质特征及矿床成因浅析

南坡金矿区地处印支陆块群墨江—黎府—罗文真火山弧带的北段,区内地质构造复杂,岩浆活动频繁.火山活动为金矿床的形成提供了丰富的物源,区域构造和派生裂隙是区内含金热液迁移的通道和容纳矿源成矿的场所.文章通过对区内矿床地质、控矿构造、矿石矿物蚀变组合特征等成矿地质条件的分析,将测区矿床成因类型暂定为地下热卤水参与的浅层低温热液黄铁矿脉构造蚀变岩型金矿床和二长花岗岩黄铁矿脉构造裂隙带蚀变岩型金矿床;从物源、成矿热动力、构造和围岩圈闭等4个成矿有利条件对南坡金矿床成因进行阐述,确立了找矿标志.     

The influences of geological and land use settings on shallow landslides triggered by an intense rainfall event in a coastal terraced environment

Several factors (including slope morphology, geological and structural settings, the mechanical properties of soils, weathering, hydrological and hydrogeological conditions and land use changes) can affect the origin and development of shallow landslides induced by rainfall. On 25 October 2011, an intense rainfall occurred in a wide area of Italy between eastern Liguria and northern Tuscany, triggering thousands of shallow landslides and causing widespread flooding. Floods and landslides caused severe damage to villages and infrastructure and caused 13 fatalities. This study was conducted to investigate the shallow landslides triggered by the rainfall in the Vernazza basin (Cinque Terre in eastern Liguria), where landslides and debris floods caused 3 fatalities and damage of approximately €130 million. The Vernazza basin, which is characterised by steep slopes, geological heterogeneity and unusual land use settings (approximately 50 % of the slopes have been terraced for centuries), was chosen as the focus of this study, conducted to assess the influences of several factors on landslide occurrence. Field surveys and engineering geological investigations, including laboratory and in situ tests, were carried out at various sites to assess the stratigraphic and geotechnical features of the soil slope covers. A basic engineering geological zoning was carried out, taking into account the bedrock lithology, the geotechnical properties of the soils and the land use settings. On the basis of a detailed inventory of the shallow landslides that occurred, the distribution of the landslides was analysed with respect to the slopes, the bedrock lithology, the land uses and the engineering geological setting. Terraced areas on impermeable bedrock were identified as the main landslide-prone areas. The results of the study also showed that the time since abandonment of terraces plays an important role in the occurrence of shallow landslides induced by rainfall.     

刚果(金)加丹加省利卡西MABEL铜钴矿地质特征及找矿方向

工作区处于刚果(金)加丹加弧形铜钴成矿带的中西部,成矿地质条件优越。根据民采线索和地质填图,圈定出一套中元古界罗安群矿山组(Pt2R2)地层,其为一套硅化结晶白云岩、含碳质白云岩、条带状硅化白云岩组合,为该区铜钴矿的含矿地层。铜钴矿以铜为主,其成因为沉积—改造型铜钴矿。对矿化带有利地段进行了验证,在标高1238～1245 m下,首次发现原生金属硫化矿,预测Cu金属量15. 32万t,Co金属量4018. 03 t。该区总体地质工作程度低,围绕罗安群矿山组地层、F2断裂南北两侧的空白地段,是下步进一步提升资源潜力的有利地段。     

东天山卡拉塔格地区火山机构地质特征

新疆东天山卡拉塔格地区近年来新发现了铜锌金多金属矿田,找矿前景良好。该区火山(熔)岩具有流纹构造、气孔和杏仁构造、柱状节理等,研究其各自特征,推测岩浆的流动方向,并由此确定了火山机构C的位置,恢复了其古地貌为一自北西向南东倾斜的火山口。由于受北西向断层的影响,火山机构C在遥感影像图上呈蝌蚪状。根据火山熔岩的岩性和构造划分为两个喷发期次:早期的裂隙式火山喷发期,晚期的中心式火山喷发期。该区具有流动构造的火山熔岩与矿体的关系密切,具流纹构造的火山角砾熔岩区域多分布有脉状的黄铜矿,具柱状节理的玄武岩分布有浸染状的黄铁矿。卡拉塔格地区火山机构C从喷发中心由内向外依次为火山颈相→火山口相→近火山口相→远火山口相。研究卡拉塔格地区火山机构的地质特征,以期为在该区开展地质找矿工作提供参考。     

安徽李营子铁矿地质特征

李营子铁矿床属沉积变质型磁铁矿,矿体赋存于吴集组上段第一、第二、第三岩性段。主要矿体呈似层状,长度为116～1700 m,斜深105～1072 m。矿体总体走向NE30°～50°,倾向NW,倾角0°～23°,沿走向和倾向局部波状起伏,有膨胀、收缩、分支、复合特点。矿石自然类型为角闪石英磁铁矿,工业类型为需选铁矿。     

贵州务正道地区铝土矿产出特征及找矿方法探讨

贵州省务(川)正(安)道(真)地区是贵州省重要的铝土矿资源产地,铝土矿矿点多,含矿岩系分布广,储藏量大,找矿前景好.近年,贵州省有色、地矿等地勘单位通过地表调查、勘查,已发现矿床(点)26处,探明大型矿床3个,中型矿床1个,提交332+ 333资源量1.3亿t.文章从该地区铝土矿的形成环境、含矿岩系变化情况及与其顶底板岩性之间的关系,探讨该区铝土矿的找矿方法.