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ザマニアハリ, ゴラムレザ ; 山口, 謙太郎 ; 宮島, 昌克
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Achour, Nebil ; Miyajima, Masakatsu ; 宮島, 昌克
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[研究概要]
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Miyajima, Masakatsu ; Setiawan, Hendra ; Yoshida, Masahiro ; Ono, Yusuke ; Kosa, Kenji ; Oktaviana, Ida Sri ; Martini ; Irdhiani ; 宮島, 昌克
概要:
金沢大学理工研究域地球社会基盤学系<br />BackgroundOn September 28th, 2018, at 18:02 local time (10:02 UTC), a strong earthquake of magnit
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ude Mw = 7.5 struck Central Sulawesi Province, Indonesia. The epicenter was located at 0.256o south latitude and 119.846o east longitude, around 77 km from Palu city, and 20 km below the ground surface. To understand the damage caused by the earthquake, and find a solution to mitigate the geo-disasters in Indonesia, a preliminary investigation on the 2018 Sulawesi earthquake was conducted from 16 to 20 November 2018. This quick report focuses on ground displacements induced by fault movement and large-scale ground flow.ResultsDuring the survey, there is some geotechnical damage were found, such as ground displacement induced by fault movement, liquefaction, landslides, and large-scale ground flow in some certain areas. Large ground displacement was found in some particular areas, such as Kedondong, Pipa Air, Pangeran Diponegoro and Cemara streets in Palu city. The earthquake also triggered large-scale ground flow in some different sites, such as Balaroa and Petobo districts in Palu city and Jono Oge and Sibalaya Villages.ConclusionsThe locations of large ground displacements appeared at surface coincide well with the estimated fault line. Therefore the large ground displacements were seems to be induced by the fault movement. Large ground flow caused severe damage to not only human but also houses and buildings. The mechanism of the large ground flow should be clarified in near future.
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Wang, Fawu ; Miyajima, Masakatsu ; Dahal, Ranjan ; Timilsina, Manita ; Li, Tonglu ; Fujiu, Makoto ; Kuwada, Yohei ; Zhao, Quanli ; 宮島, 昌克 ; 藤生, 慎
概要:
金沢大学理工研究域地球社会基盤学系<br />BackgroundThe 2015.4.25 Gorkha earthquake affected about eight million people in Nepal. Most inju
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ries 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.
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Setiawan, Hendra ; Serikawa, Yuko ; Sugita, Wataru ; Kawasaki, Hajime ; Miyajima, Masakatsu ; 宮島, 昌克
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金沢大学理工研究域地球社会基盤学系<br />BackgroundEarthquakes in liquefaction-prone areas are frequently followed by the settlement of su
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rface structures due to subsoil liquefaction. This paper aims to study the influence of geosynthetics along with gravel usage to reduce the vertical soil displacement caused by liquefaction using a shake table equipment. This influence is analyzed by means of measuring soil acceleration, pore water pressures and vertical soil deformation due to the shaking process.ResultsResults of a series of 1-g shaking table tests which have been conducted in different initial relative densities which are 50% (loose sand conditions) and 90% (dense sand conditions) to evaluate the performance of proposed mitigation against settlement problem are presented. It is found that ground settlement reduced around 11.4 mm for loose sand conditions, from 20.9 mm in the case with no countermeasure (Case 1) to 9.5 mm in the Case reinforced with gravel and geosynthetics Type II (Case 4). Correspondingly, for dense sand states, the settlement decreased by about 1.8 mm, from 5.6 mm in the Case 1 to 3.8 mm in Case 4. Moreover, a differential settlement between loose sand and dense sand conditions decreased as well, around 9.6 mm, from 15.3 mm in the Case 1 to 5.7 mm in Case 4.ConclusionsBy conducted a series of shake table tests, it is confirmed that the vertical ground displacement decreased by the use of geosynthetics and gravel up to 54% and 32% for loose sand and dense sand states, respectively. Furthermore, test results also show that there is a decrease in the differential settlement between loose sand and dense sand conditions, around 62%.
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Yang, Hufeng ; Wang, Fawu ; Miyajima, Masakatsu ; 宮島, 昌克
概要:
金沢大学理工研究域地球社会基盤学系<br />BackgroundTyphoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall. It
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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.
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Setiawan, Hendra ; Serikawa, Yuko ; Nakamura, Mitsuru ; Miyajima, Masakatsu ; Yoshida, Masaho ; 宮島, 昌克
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金沢大学理工研究域地球社会基盤学系<br />BackgroundIn April 2016, Kumamoto City, Japan, and its surroundings were hit by a sequence of str
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ong and devastating earthquakes including two significant events, one on April 14th, 2016, at 21:26 JST (Mw6.2) and the other on April 16th, 2016, at 01:25 JST (Mw7.0). These disasters caused 120 fatalities (including indirect fatalities), 2337 people injured and 177,914 residential houses were damaged. This paper aims to ascertain the damage to residential houses and buildings caused by liquefaction during this earthquake and suggests possible mitigation methods.ResultsField reconnaissance was conducted in the target area on May 27th–30th, 2016. The post-earthquake inclination angle and the tilt direction of 68 affected houses and buildings in the liquefied sites in Kumamoto City were measured by using a laser rangefinder (Leica DISTO D 510). Ground structure and condition were also determined from topographic maps, bore data and the calculated liquefaction resistance factor, FL.ConclusionsBased on this investigation, the inclination angle of the houses in the target area seems to be related to the type of building structure and their foundation as well to the local ground composition. The tilt direction has a tendency to be associated with the location of the nearby river. The results presented could be useful to develop future liquefaction mitigation measures for detached residential houses.
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Karimzadeh, Sadra ; Matsuoka, Masashi ; Miyajima, Masakatsu ; Adriano, Bruno ; Fallahi, Abdolhossein ; Karashi, Jafar ; 宮島, 昌克
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金沢大学理工研究域地球社会基盤学系<br />In this study, we used fifty-six synthetic aperture radar (SAR) images acquired from the Sentinel
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-1 C-band satellite with a regular period of 12 days (except for one image) to produce sequential phase correlation (sequential coherence) maps for the town of Sarpole-Zahab in western Iran, which experienced a magnitude 7.3 earthquake on 12 November 2017. The preseismic condition of the buildings in the town was assessed based on a long sequential SAR coherence (LSSC) method, in which we considered 55 of the 56 images to produce a coherence decay model with climatic and temporal parameters. The coseismic condition of the buildings was assessed with 3 later images and normalized RGB visualization using the short sequential SAR coherence (SSSC) method. Discriminant analysis between the completely collapsed and uncollapsed buildings was also performed for approximately 700 randomly selected buildings (for each category) by considering the heights of the buildings and the SSSC results. Finally, the area and volume of debris were calculated based on a fusion of a discriminant map and a 3D vector map of the town.<br />CC-BY 4.0
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Kiyono, Junichi ; Fujiwara, Tadafumi ; Hamada, Masanori ; Hashimoto, Takao ; Ichii, Koji ; Isoyama, Ryoji ; Konagai, Kazuo ; Miyajima, Masakatsu ; Murakami, Hitomi ; Nakamura, Susumu ; Nozaki, Tomofumi ; Taji, Yoichi ; 宮島, 昌克
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金沢大学理工研究域地球社会基盤学系<br />Damage done to civil structures by the 2000 Tottori-ken Seibu Earthquake was investigated. Field
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surveys were made from October 8-10 by eight members dispatched by the JSCE in cooperation with other researchers. Descriptions are given of the earthquake, seismic ground motion; the damage done to such civil structures as roads, road bridges, lifelines, dams, port facilities; slope failures; and public risk management. Although peak ground accelerations were extremely intensive, structural damage was not as severe as compared with the average damage caused by past earthquakes in Japan. Such disaster responses as search and rescue activities, emergency responses, disaster information communication, and victim supports are discussed.
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Bourzam, Abdelkrim ; Goto, Tetsuro ; Miyajima, Masakatsu ; 宮島, 昌克
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金沢大学理工研究域地球社会基盤学系<br />This study describes an analytical proposal to predict lateral shear capacity of confined masonry
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walls that fail by diagonal splitting, where the maximum shear is evaluated as the dowel action of confined columns' reinforcement added to the shear capacity of the plain masonry panel. In order to validate the proposed approach, experimental test results and gathered data from literature were used. The experimental tests concerned two confined clay brick walls subjected to different level of gravity load and cyclic lateral loading. The applicability of some empirical formulae found in literature regarding the stiffness degradation was investigated. Good correlation between the predicted lateral resistance using the proposed approach and all data was achieved.
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