A series of stability analyses of cohesive soil slopes was conducted by means of limit equilibrium method to clarify the effects of three-dimensional shapes of sliding mass and slope on the slope stability. In the analyses, straight and curved slopes consisting of frictionless soil were considered; the curved slopes were defined with concentric circles instead of straight lines, and sliding surfaces were defined with spheroid. Through the analytical investigations some important features of three-dimensional slope stability were found. Even straight slope with finite width has a critical sliding depth with notably higher stability factor than that of with infinite width that shows the lowest stability at infinite depth as in ordinary two-dimensional analysis. Curved slopes have their own critical sliding width depending on its curvature. We updated the stability diagram presented by Terzaghi with three-dimensional effects taken into account.

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A box culvert (C-Box) is placed over the road in order to allow traffic to cross over a small river or other roads. Currently, two types of frost heave damage in cold districts are being reported: cracks that are generated when the road surface, which is directly on the C-Box, is lifted like the mound, and cracks that are generated in the sidewall by the frost heaving pressure. In the investigation to determine the mechanism of these damages, we set an embankment model in a large-scale low temperature room, and compared the results of soil temperature measurements and those of 2-dimensional FEM heat conduction analysis. As the result of these experiments and analyses, the soil temperature distributions and progress of freezing fronts (0 degrees centigrade) in the soil around the C-Box were reproduced. It was revealed that frost entered the soil around the C-Box from the inside of the C-Box as well as from the surface of the embarkment, and this frost caused the shape of the freezing front to interfer with each other, which generated a bigger frost heave.

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Applicability of the Piezocone penetration test (CPTU) for estimating various soil parameters such as SPT-N value, unconfined compression strength, pre-consolidation pressure, soil classification, liquefaction criteria and so on is examined through comparison of CPT data with results of SPT, Swedish Weight Sounding (SWS), soil tests such as oedometer tests, unconfined compression tests and sieving tests. It was shown that various soil parameters estimated from CPTU conformed well to the measured results, compared with the performance of SWS.

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Construction wastes such as concrete and asphalt have been reduced, recycled and reused. However, scraped woods are not sufficiently recycled. Attempts to improve material property of the scraped woods by adding biodegradable plastics (PLA) have been made in various fields. In this study, an applicability of biodegradable material for drainage layer in fill material was investigated. A granular material with biodegradability was buried under a ground during different periods in order to change degree of biodegradation. Mechanical behavior of the granular material was examined by various soil testing. Main conclusions are as follows. 1) Biodegradable rate of the granular material is low as compared with other materials. 2) Compression and tensile strengths of a single particle decrease with increasing the duration in which the material was buried in the ground. 3) Influence of deterioration due to biodegradation on drained shear and cyclic strengths as particulate media is not recognized.

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Recently, impact to society by global warming is attracting greater attention in all the world. It is afraid that the global warming is bringing sea-level rising and increases of heavy raining and storm. The IPCC prefigures that the maximum amount of rising sea-level due to global warming will be 59 cm. It is also prefigured that brackish-region in rivers will expand by running of seawater to the upside of rivers. If the above phenomenon will appear, it is afraid that levees and riverbanks made by soil material are affected by seawater. From the background, it is required to evaluate vulnerability of levees and riverbanks as infrastructures in Japan. This study investigates changes of properties of soil materials, which is used to construct levees and riverbanks, by water chemistry in laboratory. The laboratory experiments use the distilled water assuming fresh-water, and the artificial seawater assuming brine-water and brackish-water. From the laboratory experiments, this study evaluates vulnerability of levees and riverbanks as infrastructures by sea-level rising due to global warming.

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In the research of extensive and multifaceted disasters such as earthquake disasters, grasp of disaster points and damage conditions, plus the information sharing are most important. This greatly contributes to damage reduction. However, getting to the very important location sometimes becomes difficult due to by-passing sections blocked by collapses of embankments or slopes. Moreover, the drivers may be endangered by searching various signposts and disaster points. In order to ensure safe investigation, rapid location searching, recording, and information sharing, we developed a new disaster investigation support system on the basis of our experience in the research of earthquake disasters. We utilized this system for the geotechnical examination of the heavy rain in October 2006, and verified its effectiveness. The system could be employed in periodic inspection of slopes and aerial investigation.

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Ground freezes from the surface downward, and during this process soil moisture is drawn upward. The moisture content of soil that has frozen is high, whereas the moisture content of non-frozen soil below that is low, because water is drawn upward toward the soil that has frozen. If high-moisture soil can be improved to yield low-moisture soil using this phenomenon, low-cost improvement will be possible. Moisture can be reduced by repeated freezing and thawing, changes in soil temperature, then, soil moisture change through winter were monitored in outdoor experiments. It was shown that unsuitable soil could be improved by repeated freezing and thawing, that the decrease in moisture content was finished within one season.

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This article proposes an efficient way of routine investigation for maintenance of the structure against falling rock based on the site simulations using a mobile GPS device. The simulations of investigation were conducted on the rope net countermeasures at ten locations by two technical groups. We compared trip time to reach the investigation site for two groups. Group-A carried only the site map as the information. On the other hand, Group-B carried the map and mobile GPS device. As a result, the total trip time by Group-B was shortened by 42% in comparison with Group-A. It was found that the mobile GPS device helped the staffs to get to the destination. The GIS system with GPS coordinate information about the locations of the infrastructures will make it possible for engineers to easily manage the integrated data and to share the detailed information about access route. In addition, that system will make it possible to plan the maintenance survey easily.

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