Abstract: Geological risk of bridge foundation rock is discussed on the basis of case study for short-span and long-span bridges. Over/underestimation of geological and geotechnical conditions arise for most of studied bridge foundations and this geological risk often produce cost loss. Because difficult geological conditions cause noticeable estimation error of bridge foundation rock, improvement of investigation and analysis method is necessary.
Keywords: geological risk, bridge foundation rock, geological estimation and practice, over/underestimation, cost loss
p. 67- 75

Abstract: This paper is consists of two parts. Firstly, an overview is given for landslides on areas underlain by serpentinite and ultra-mafic rocks throughout Japanese island arcs. Major areas underlain by those rocks are Kamuikotan belt in Hokkaido, and Renge or Oeyama belt in western part of Honshu of the Inner Japan. Minor areas are found along Hayachine tectonic zone in northeast Tohoku of northern Honshu, Sambagawa belt, and Kurosegawa tectonic zone of the Outer Japan. Landslides are found in areas underlain by specific types of serpentinite in sheared zones, or contact zones with other rocks along faults. Secondly, detail aerial photo-interpretation is shown on Odokoro-Kijiya landslide at the northern part of North Alps of central Japan developed at the area composed of serpentinite and in addition a few landslides in the nearby areas underlain by similar rocks. A serpentinite rock body of scaly or phyllitic type in sheared zones, specifically contacting with other geologic bodies by faults, shows high susceptibility for landslides but very low of block type not contact with other geologic bodies. As the most of serpentinite rocks are considered as products of hydration of a wedge mantle along a Wadati-Benioff zone from a subduction of an oceanic plate, we have, through this study, approached in conclusion to an idea that those landslides on serpentinite rock bodies are fundamentally related to geologic structure and tectonics related to construction of island arcs.
Keywords: landslides, serpentinite, geologic structure, island arcs, Odokoro-Kijiya landslide
p. 77-118

Abstract: Soon after the Earthquake Disaster in the East Japan in 2011, the Asahi Shimbun reported the presence of the old documents that a tsunami following the Tansho Earthquake in 1586 hit the Wakasa Bay in Western Japan and the surrounding areas were suffered heavy damage. According to the article, the sentence that the beach along the Wakasa Bay in Tango District suffered by a tsunami is documented in “The Diary of Sir Kanemi”. According to the instructions from the Nuclear Safety Commission, Kansai Electric Power Co. Inc. and other two electric power companies conducted researches to get sediment cores by boring in the Wakasa Bay to clarify the presence or absence of seawater intrusion into the bay caused by the historically documented tsunami. Sediment cores from the Kugushi and Suga Lakes in the Mikata Five Lakes reveal the absence of such seawater intrusion into these lakes. Geologically speaking, these researches gave reliable evidences to deny the presence of supposed occurrence of “Wakasa Bay Tsunami following the Tensho Earthquake in 1586”. After reexamination of “The Diary of Sir Kanemi”, the words “the surging waves” were documented but the word “tsunami” was not used. When the Institue of Historiography of the University of Tokyo edited “The Historical Documents of Japan”, “The Diary of Sir Kanemi” was also involved in it and a historiographer commented annotation as “the beach along the Wakasa Bay in Tango District suffered by a tsunami”. Asahi Shimbun reported the presence of the sentence regarding the tsunami in the Wakasa Bay as if the sentence was appeared in “The Diary of Sir Kanemi”. In “The History of Japan” published by Luis Flois, the words “high waves” were expressed but the word “tsunami” was not appeared either. At the same time as the Tensho Earthquake occurred in 1586, heavy waves might have been generated by strong seasonal winds of winter time along the Japan Sea. Without clear discrinimation between tsunami and flood tide or high wave, a historiographer might have expressed the word “tsunami” for flood tide or high wave. An ambiguous usage of “tsunami” is regarded as the prime factor to introduce the confusion about the Wakasa Bay Tsunami.
Keywords: Tensho Earthquake, Wakasa Bay Tsunami, Diary of Sir Kanemi, Mikata Five Lakes, Tsunami Deposits
p. 119- 137

Abstract: The numbers of the house collapse and the dead person according to the municipalities caused by the 1923 Kanto earthquake in “Taisho Shinsai Shi (The report of the Great Kanto Earthquake, edited by the Department of the Interior Social Welfare Bureau 1926) were collected and made distribution maps of them. The areas where the number of the house collapse was big in (1) the area just above the fault plane; plain areas in Kanagawa prefecture and on the top of the Boso peninsula, in (2) Kofu and Fuji Goko basins which had been parts of lake areas in geologically ancient years, and (3) in Southeast Saitama prefecture which had been was flooding plains of the Former Tone River before the beginning of 17the century. There were many death tolls in (1) and (3), too, but there were few death tolls in (2). On the contrary, the place where there were many death tolls although there was little number of the house collapse existed in the natural levee plains of the former Tone and Arakawa rivers in the area of the north part of Saitama Prefecture. In such area as the area (2), houses were collapsed by long period vibration so, the residents took enough time to refuge measures. On the contrary, it is thought that the house collapsed instantly at the place where there were many death tolls.
Keywords: the 1923 Great Kanto earthquake, the number of the house collapse, the death toll, earthquake disaster damage concentration in the former wetlands ground, natural levee
p.139- 145

Abstract: Sandpile experiments have been performed using, not a circular, but a polygonal (octagonal) disk. Thus the pile becomes a pyramid, the surface of which is divided into several segments. Each segment is considered to be an individual surface. Avalanches sometimes occur on a single segment and sometimes on several segments simultaneously, resulting in a large avalanche which is regarded as a consecutive event. We used an WEB camera which takes images of the sandpile with a constant interval, in order to identify the location of avalanches by comparing the two images taken before and after a large avalanche. A large avalanche occurs as a result of successive collapses of adjacent segments. We found that when the drop point of sand onto a sandpile misses the center of the disk, the occurrence of large avalanches becomes periodic and regular because the same segments collapse every time, whereas when it matches the center of the disk, it becomes irregular so that it is very difficult to forecast the time and the magnitude of the next avalanche. However we found that the main segment of the next avalanche becomes calm (quiescent) just before the avalanche. The elucidation of detailed mechanism of the quiescence will be a future work.
Keywords: sandpile experiment, avalanche, consecution, segment, quiescence
p. 147- 156

Abstract: 4th Central Asian Geotechnical Symposium was held in Samarkand. It intended to discuss and exchange ideas on geotechnical problems as well as conservation of heritage and historical sites. Samarkand is one of the most important cities and the World Heritage sites in Uzbekistan. There are many historical sites, and some of them contain geological and geotechnical problems, for example salt weathering and soft ground. This report introduces abstract of the symposium with abundant beautiful photographs.
Keywords: cultural heritage, conservation, preservation, salt weathering
p. 157- 164

Abstract: For developing an effective method to estimate permeability of soils and rocks using geophysical data, we have studied the Koseny-Carman equation (K-C equation) with porosity and grain size estimated from geophysical data based on rock physics models. For application of the proposed method to saturated soils, S-wave velocity and resistivity logging data are input to the unconsolidated sand model and the Archie’s equation for estimating porosity and grain size of the soil, which are employed in K-C equation to calculate permeability. Comparison of estimated permeability with actual measurement by in-situ permeability test shows that permeability is estimated in accuracy less than one order of magnitude for 78 % of the compared data. For application to sandy siltstone, S-wave velocity and density logs are employed in the bimodal mixture model to estimate clay content, which can be used for calculating grain size. The grain size thus obtained and porosity derived from density are utilized for calculating permeability with K-C equation. Permeability estimated in accuracy less than one order of magnitude is only for 53% of the compared data.
Keywords: rock physics, geophysics, permeability, Koseny-Carman equation
p. 165- 172

Abstract: In recent years, 3D geophysical exploration has begun to be applied to detailed investigation of river embankment. In order to present geophysical data on river embankment clearly, we performed 3D visualization of them using Voxler®, a 3D imaging software. This paper describes its operating procedures with some examples of 3D images such as block diagram, panel diagrams, isosurface views and cross-sectional views commonly used in presenting geophysical data.
Keywords: Voxler, geophysical exploration, river embankment, 3D visualization
p. 173- 186