The purpose of this research is to clarify the evaluation of the bearing capacity of a pile with multi-stepped two diameters. Model tests were conducted by driving multi-stepped type metallic piles into two kinds of dry ground to evaluate the bearing mechanism. The following points about the pile with multi-stepped two diameters were confirmed; i) for the bearing capacity of the convex part, the failure mechanism is classified into two categories depending on difference in the concave part length, and ii) the normal pressure on the shear surface around concave parts is bigger due to the bearing effect of the convex part. Quantitatively, the procedure used the spherical cavity expansion method offers potential for better prediction of the pile with the long concave part. Considering the bearing effect on the base of the convex part, another procedure could be good predictions for shear resistance around the short concave part in the sand ground.

View full abstract

This study examined basic concepts and regulations on the fundamental performance of hydraulic ability and water serviceability for irrigation canal systems in performance based design and projects. Methods of verifying the performance of an existing system and the water serviceability design solution are arranged and criterion indexes, which are performance based design targets or evaluation indexes, are proposed. The regulatory principle chiefly conforms to the comprehensive foundation design code (Geocode 21) of the Japanese Geotechnical Society. The basic functions of this system are classified into six main types including the environment in a broad sense. Each function is defined from a basic regulation, and a tentative plan for making a layered structure is shown. The water conveyance and distribution ability, scheme management method and hydraulic conveyance ability are identified as basic performance requirements. Irrigation efficiency, travel time of water and total lifecycle cost subordinated to the hydraulic head allocation of the systems are set as indexes for water conveyance and distribution ability. The performance of each item varies according to the pattern, and an example of each performance index is introduced.

View full abstract

The microwave backscattering coefficient of ground covered with dry snow was observed at incidence angles of 25°, 35° and 45° using a C-band microwave scatterometer in winter in Sapporo, and relationships between the observations and snow water equivalent were examined. As a result, although the observations of each incidence angle did not show a correlation with the snow water equivalent, the differences between the observations at 25° and at 45° had a significant correlation with the snow water equivalent. This result shows possibility of estimating the snow water equivalent of dry snow pack using C-band multi-incident angular data with a Synthetic Aperture Radar (SAR) mounted on a satellite. From analysis using a backscattering model, it was guessed that an immediate factor in the increase of differences between observations at 25° and at 45° with the increase of the snow water equivalent was the change of the roughness condition of the soil surface (discontinuous plane of the dielectric constant) under dry snow pack. It was thought that this change of the roughness condition occurred along with snowmelt at the base of a snow pack.

View full abstract

Agricultural damage caused by wildlife is expanding to a nationwide scale in Japan. The ministry of agriculture, forestry and fisheries recommend the attempts to decrease agricultural damage caused by wildlife under the residents'cooperation instead of the attempts by an individual. This paper focuses on the relation between farmers' intentions to carry out the measures to decrease agricultural damage caused by wildlife and thecharacteristics of farming communities based on the questionnaire survey conducted in 14 farming communities of Wakayama prefecture in 2007. As a result of cluster analysis, the following characteristics of farming communities have connection with the following farmers' intentions; 1) the farming communities, which the ratio of paddy field to the total farmland is low and most of farm households are full-time, each farm household manage large farming scale, show the tendency that most farmers intend to carry out by plural farmers. 2) The farming communities, which decrease the number of farm households and acreage of farmland, show the tendency that most farmers intend to carry out by all residents. 3) The farming communities, which the ratio of paddy field to the total farmland is high and farmland consolidation was conducted, show the tendency that few farmers intend to carry out by individuals.These results tell the necessity of the considering to the characteristics of farming communities in the introduction of the measures.

View full abstract

Most of old fill-type dams were mostly needed the rehabilitation of the embankment by aging and accumulated with the muddy soil in reservoir that caused the water pollution and the loss of reserved water. In order to make efficient use of the muddy soil as the embankment soil, we have developed a new type method to rehabilitate the old fill-type dam embankment.
In this paper, we propose a new design method to rehabilitate the old fill-type dam embankments by constructing the sloping core and shell zones using the cement-mixed muddy soil for reinforcing the damaged embankment. The feature of the design method are introduced the strength control system considering the effect of the grading and the water content on the strength of cement-mixed muddy soil, and adopted the strength parameters (c', φ') using the bi-linear type failure criterion obtained from the tri-axial compression tests to evaluate exactly the strength characteristics at wide range stress levels of the cement-mixed muddy soil.

View full abstract

The mechanism of the generation and development processes of the gravity convection induced by water surface cooling were investigated through the flow visualization experiment and the water temperature measurement experiment for a closed density stratified water body covered with aquatic plants. When a part of the water surface is covered by aquatic plants, etc, the waters are inhomogeneously cooled, and the turbulent intensity in each area has changed greatly. The horizontal convection driven by this horizontal density difference greatly influenced the development speed of the mixed layer. And it is understood that the characteristic of the mixed layer in the covering part depends on the parameters; the heat flux from the water surface, temperature descend speed in the mixed layer, the thickness of the mixed layer and the horizontal convection velocity.

View full abstract

Preliminary study using microsatellite DNA loci, namely DNA markers, were conducted to elucidate genetic structure of the Japanese eight-barbel loach, Lefua echigonia populations in the upper Kokai River basin, Tochigi Prefecture. 17 existing and two new loci were tested with eight specimens each of five populations collected from the Kokai River and one from the neighboring Ara-kawa River. A total of 12 loci were used for genetic analysis. The average number of alleles per locus was 4.4-5.3 and the average observed and expected heterozygosities were 0.527-0.661 and 0.581-0.657, respectively, across the six populations. All populations had similar levels of genetic diversity and did not depart from the Hardy-Weinberg equilibrium. Genetic differentiation between populations in the Kokai and Ara-kawa Rivers (F_ST=0.147) was higher than an any the Kokai River populations (F_ST=0.078), suggesting that genetic properties of the sampled populations appeared to differ among river basins.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract