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,...     

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...     

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。     

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.     

Simulating dynamic processes and hypermobility mechanisms of the Wenjiagou rock avalanche triggered by the 2008 Wenchuan earthquake using discrete element modelling

The discrete element method is well suited for simulating the cracks and subsequent large displacements of catastrophic landslides or rock avalanches, and is therefore a useful tool for analysing their complicated dynamic processes and hypermobility mechanisms. In this study, particle flow code was used to investigate the dynamic processes and hypermobility mechanisms of the Wenjiagou rock avalanche triggered by the 2008 Wenchuan earthquake. Characterization of the avalanche dynamics was achieved using a model comprising four stages: failure rupture, projectile motion, granular debris flow, and debris mass accumulation. The results show that collision on the valley floor was the main factor causing the fragmentation of the Wenjiagou rock avalanche. The upper and front edge of the landslide body were the most likely to move over a long distance. The results also show that friction was the main source of energy dissipation during the entirety of the avalanche movement. The high gravitational potential energy of the avalanche was the basis of the high mobility. In addition, because of their effects on energy dissipation, the low basal friction coefficient, favourable block movement, and topographical conditions played key roles in the rapid, long-runout Wenjiagou avalanche process.     

降雨条件下滇西典型土质滑坡渗流特性分析

降雨是诱发滇西土质滑坡灾害的主要因素,选择滇西红层典型土质滑坡——思铺滑坡做深入的调查,考虑降雨入渗的影响,基于饱和-非饱和渗流理论,利用有限元方法,对强降雨条件下思铺滑坡地下水渗流场动态进行了数值模拟,得到了滑坡地下水压力水头、总水头变化、流速的变化规律,为滑坡的稳定性分析和滑坡预测提供重要的分析数据。     

日本地下石油储藏的岩体特征分析

日本岛是环太平洋地区的一部分,位于欧亚板块、太平洋板块和菲律宾三大板块的交接处.在这一复杂的地质构造区域,一些欧洲的地质学家十分怀疑是否能在这种脆弱的地层中布置大规模、长距离的隧道进行石油储藏,但是,储藏量达500万kl的串木野、菊间、久慈三个大型地下石油储备基地的成功运行,证明了在日本这样脆弱的地层中储藏石油是可行的.由于我国东部沿海地区与日本岛在地层和地质特征方面具有相似性,因此分析日本地下石油储藏的岩体地质条件,对我国目前正在该区域进行的地下石油储藏具有重要的指导意义.     

云南华坪基度大理石矿地质特征及矿床成因分析

云南华坪基度大理石矿赋存于上扬子古陆块盐源-丽江被动陆缘北部中二叠统阳新组地层中,岩性为隐晶-微晶灰岩、含生物碎屑灰岩.矿体受层位、岩性、岩相等因素控制,产出稳定,矿床规模大型.矿石有瓷白、米黄、银灰三个品种类型.受构造、节理裂隙和风氧化作用影响控制,品种上乘、质量优良.矿床为中二叠世沉积的一套开阔台地相碳酸盐岩,经成...     

Statistical analyses of landslide size and spatial distribution triggered by 1990 Rudbar-Manjil (Mw 7.3) earthquake,northern Iran: revised inventory,and controlling factors

Bulletin of Engineering Geology and the Environment - This study is a revised inventory of landslides triggered by the Rudbar-Manjil earthquake (Mw = 7.3), 1990, obtained through the...     

Geological and geotechnical characteristics of Karameh dam site, north of the Dead Sea, Jordan

This paper describes a feasibility stage geotechnical evaluation carried out at the Karameh dam site. The 45 m high, 2,150 m long dam will be built across the Wadi Mallaha on Quaternary lacustrine deposits and store fresh water from the King Abdullah Canal. A confined highly saline aquifer was identified at a depth of 25 m, the saline groundwater migrating naturally through the Lisan Formation. Stability analysis of the foundation indicates that the slopes are just stable under dry conditions and may become unstable under wet conditions. The most important problem is the presence of the active main Jordan Valley Fault crossing both the dam body and reservoir. Electronic Publication     

Analysis of the geo-hazards triggered by the 12 May 2008 Wenchuan Earthquake,China

The Wenchuan Earthquake on 12 May 2008 triggered a large number of geo-hazards including landslides, slope collapses and debris flows. Field investigations and remote-sensing interpretation identified 11,308 geo-hazards in 16 seriously damaged counties in Sichuan Province, south west China. The paper reports an analysis of the distribution of these geo-hazards, particularly the earthquake-triggered landslides. Not surprisingly, the most significant geo-hazards were related to the main fault and on the hanging-wall side, although some occurred in deeply incised river gorges further away from the main rupture zone. Due to the high seismic intensity of the earthquake, most of the large landslides moved at high speed and for considerable distances.     

Deformation characteristics,mechanisms, and influencing factors of hydrodynamic pressure landslides in the Three Gorges Reservoir: a case study and model test study

Bulletin of Engineering Geology and the Environment - Hydrodynamic Pressure landslides are the most typical landslides affected by the water level in the Three Gorges Reservoir. These types of...