Influence of reservoir water level variation on slope in lab. flume test

The Tenth International Symposium on Mitigation of Geo-disasters in Asia. Kyoto Symposium. Place: Uji Campus, Kyoto University. Date: 7 October 201

Deforming mechanism and influential factors of giant Jinnosuke-dani landslide, Japan

Synopsis The Jinnosuke-dani landslide is a giant landslide with a scale of 2000 m in length and 500 m in width in Haku-san mountainous area, Japan. This landslide consists of alternative layers of sandstone and shale in Tetori Group that deposited from Mesozoic Jurassic period to Early Cretaceous period. Based on deformation monitoring results for more than seven years, the landslide is divided into upper block and lower block. The upper block moves at a relatively high speed (80 mm to 170 mm / year), while the lower block moves slowly (3 mm to 15 mm / year). Monitored data also show that the variation of the groundwater level has a great influence on the landslide movement. The effects of the weathering of the alternative layers of sandstone and shale on the landslide deformation were confirmed through numerical analyses

Assessing the internal structure of landslide dams subject to possible piping erosion by means of microtremor chain array and self-potential surveys

An integrated geophysical approach comprising microtremor chain array and self-potential surveys was used to assess the internal structure of landslide dams subject to possible piping erosion in selected sites in Japan and Kyrgyzstan. The non-invasive geophysical approach is cost effective, environmentally friendly and portable, and hence, it has proven to be valuable for the geotechnical assessment of landslide dams where piping can trigger failure of the dam. While the microtremor chain array survey results revealed the internal structure of the landslide dam, the self-potential survey results indicated the path of anomalous seepage zones. In the surveyed sites of long-existing landslide dams, the presence of a seepage path in the dam was confirmed by a good correlation between the areas of low phase velocity and large negative self-potential anomalies. In summary, this integrated geophysical approach could be useful for the early risk assessment of landslide dams and prediction of landslide dam failure by piping

Experimental study to identify premonitory factors of landslide dam failures

Identifying premonitory factors before final failure for long-existing landslide dams is of high importance in disaster prevention and risk reduction. In this study, a series of large-scale (outdoor) experiments were designed and conducted to identify premonitory factors that may be used in failure prediction for actual landslide dams. Surface deformation, especially dam-crest settlement, dam seepage-water turbidity and self-potential across the dam crest were selected as the target parameters. Changes in these parameters showed apparent correlations between each other. Based on the monitoring data obtained and the observation performed during the tests, the deformation and failure sequence of the dam model can be separated into four time-sequential periods: 1) Emergence of seepage water and front wetting. In this period, the monitoring parameters did not show any obvious changes. However, wetting was observed in the downstream face. 2) Hyperconcentrated flow discharge. In this period, water flowed out of the drainage channel, and the vertical deformation of the dam body became obvious, while the turbidity of the seepage water increased. 3) Emergence and development of cracks on the dam crest. In this period, the dam-crest settlement also increased. 4) Sudden collapse and final failure. In this period, self-potential across the dam crest decreased rapidly, and the dam-crest settlement reached a peak value. Therefore, dam-crest settlement, seepage-water turbidity and self-potential changes can be regarded as premonitory factors of landslide dam failur

Investigation of shallow landslides triggered by heavy rainfall during typhoon Wipha (2013), Izu Oshima Island, Japan

金沢大学理工研究域地球社会基盤学系BackgroundTyphoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall. It triggered widespread landslides on the western slopes of Izu Oshima Island, and caused significant loss of life and serious property damage. Authors have conducted both field investigations and laboratory experiments in an effort to understand the initiation mechanism of the shallow landslides triggered by heavy rainfall.ResultsPyroclastic-fall deposits on the slopes are well-graded fine sand with silt, and with high specific gravity and void ratio. These soil properties will affect the mechanical and hydraulic characteristics of soil. The results of consolidated-undrained triaxial tests show that the effective internal friction angle of soil is 38.7 degrees. The results of triaxial tests using pore-water pressure control show that static liquefaction can occur in porous pyroclastic-fall deposit layers due to rainfall infiltration.ConclusionsThe effective strength of pyroclastic-fall deposits on the upper slope is quite high. Even though the slope is very steep (over 30 degrees), it can remain stable while in an unsaturated condition. Due to heavy rainfall and the porosity of the pyroclastic-fall deposits, rainfall can quickly infiltrate into soil layer. Moreover, the interface above the underlying basalt will stop groundwater infiltration, acting as an impervious boundary. With increase of groundwater level, the effective strength of the porous soil will decrease. Finally, static liquefaction can be triggered, leading to the generation of shallow landslides on the upper slopes

Effects of topographic and geological features on building damage caused by 2015.4.25 Mw7.8 Gorkha earthquake in Nepal: a preliminary investigation report

金沢大学理工研究域地球社会基盤学系BackgroundThe 2015.4.25 Gorkha earthquake affected about eight million people in Nepal. Most injuries and loss of life were due to building collapse and damage. This work aims to investigate the topographical and geological effects on the severe damage caused by this earthquake.FindingsIn one-week field investigation in the earthquake-affected areas, several severely damaged areas with different topographic and geological features were surveyed, as well as the site of Kaligandaki River landslide dam failure. Some general tendency related to the building damage and landslide dam failure was obtained.ConclusionsThrough the field investigation, it was found that geological and geomorphological characteristics of a site, combined with the structure feature of the building, such as the short column effect, amplified the seismic vibration and caused severe building collapse and damages, i.e., 1) For buildings on flat area consisting of lacustrine deposit or diluvial deposit, resonance effect might be the main reason, while for the buildings on the top of hills or narrow ridges, topographic effect and sometimes, short column effect should take the main responsibility; 2) For buildings located on the gentle slopes or landslides, the settlement in the infill side caused by the strong seismic vibration can be the main reason; 3) Besides of the building failure on lacustrine deposit, failure patterns in three types of topographic and geological features, i.e., narrow ridges formed by landslides, diluvial deposits and alluvial fans, and landslides, were proposed as the possible mechanism of the building damage caused by the earthquake. For landslide dam failure, it was found that landslide dam could easily breach or collapse, when the landslide-dam-deposits were fine

Acknowledgements to referees in 2016

Abstract In 2016, Geoenvironmental Disasters published 29 scientific articles. Besides the appreciation to the authors who contributed their works to the journal, we want to express our sincere acknowledgement to the referees, who actively supported the journal with their expertise during peer review. Their qualified and constructive contributions to the journal are respected and appreciated

せん断中の砂質土の粒子破砕と過剰間隙水圧発生特性の実験的研究 : 地すべりの高速運動の基礎的要素

京都大学0048新制・課程博士博士(理学)甲第7668号理博第2053号新制||理||1092(附属図書館)UT51-99-G262京都大学大学院理学研究科地球惑星科学専攻(主査)教授 佐々 恭二, 教授 千木良 雅弘, 教授 奥西 一夫学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

Experimental study of submarine landslides -Motion mechanism and impact force to cable-

The Tenth International Symposium on Mitigation of Geo-disasters in Asia Matsue Symposium Place: Shimane Civil Center, Matsue Date: 8 October 201