Kojima湖表层水的腐殖质特征

Humic compounds are one of the major substances that affect the COD value of the surface water of Lake Kojima. The humic compounds in the lake water were studied with a spectrofluorophotometer. The 3-dimensional fluorescence spectrum suggests that two kinds of fluorescent substances exist in the lake water. One shows an fluorescence excitation maxim (Ex) at about 240 nm and an emission maxim (Em) at 413 nm. The other has an Ex at 330 nm and an Em at 418 nm. The former peaks are associated with humic acid and the latter peaks are associated with fulvic acid. These peak intensities are proportional to the COD values. The fulvic acid in the lake water may be enriched by the effluent from domestic water treatment plants.     

Use of lateritic fine-grained soils in road pavement base courses

Summary Lateritic fine-grained soils are, in large areas of Brazil and other tropical countries, the most frequent local materials found along road routes. However the use of these soils in pavements has been difficult, because they do not conform to the traditional specifications for base courses. This paper presents successful uses of many of these soils in pavement base courses, particularly sandy soils, following specially developed geotechnical test methods and construction procedures, thus sensibly reducing the cost of pavements, mainly for low to medium traffic levels.     

Transient response of finitely long cylindrical cavity with arbitrary cross-section

A semi-analytical boundary element method is developed for the efficient time-domain dynamic response analysis of a finitely long cylindrical cavity with an arbitrary cross-section geometry. High computational efficiency is achieved by mapping a complex shape of the cross-section into a circular shape. For this purpose a special coordinate transformation equation is presented. This mapping enables us to discretize the boundary element equation only along the longitudinal axis of the cavity. The versatility and accuracy of the method are amply demonstrated through a number of examples. The transient stresses and displacements are found to be considerably influenced by the slenderness ratio, length over diameter of the cavity and the incidence angle of the incident wave.     

Earthquake induced hydrodynamic pressure on axisymmetric offshore structures

The horizontal earthquake induced hydrodynamic pressure acting on the surface of axisymmetric offshore and coastal structures is explored. A semi-analytical and semi-numerical approach based on the use of a complete and non-singular set of Trefftz functions is developed. Using this method, one can model accurately the compressibility of the sea water and gravity waves on the water surface. The proposed method shows a relatively simple and efficient approach. This is because the number of degrees of freedom in the matrix equation depends only on the number of selected Trefftz functions and because the discretization of the fluid domain into boundary elements is restricted to the structural surface only. This method is also easy to apply in engineering analysis of hydrodynamic pressure induced by an actual earthquake acceleration. Numerical examples are presented to illustrate the results obtained from this method. Several special interesting topics, such as the effects of the water compressibility, the gravity waves on the water surface and the geometrical shape of the structural surface, are also discussed.     

The domain of validity of the KdV-type solitary rossby waves in the shallow water β-plane model

The Domain, where the necessary and sufficient conditions for the existence of the KdV-type solitary Rossby waves are satisfied is defined in the shallow water β-plane model. The KdV-type solitary Rossby waves are the Rossby waves whose time-longitude dependence is determined by the KdV equation. As far as an appropriate amplitude and an appropriate ratio of the scales of the east-west and north-south directions are given, the KdV-type solitary Rossby waves can exist for every basic zonal flow. This result suggests the large validity of the soliton model in geophysical fluid dynamics. The KdV-type solitary Rossby waves are classified into four categories: (1) shear solitons studied by Long, Larsen, Benny, Redekop, and Hukuda, (2) β-divergent solitons studied by Clarke, Yamagata, and Nogami, (3) β-solitons found in the case of the strong stratification, and (4) divergent solitons which exist in the planetary-geostrophic-scale zonal flow. A remarkable result is that, in addition to the conventional east-west elongated solitons, the north-south elongated solitons can also exist for the case of the divergent solitons.     

Resistance of soil to a horizontally vibrating pile

The resistance of a soil layer to steady horizontal vibration of an elastic pile is theoretically investigated. The pile is assumed to be vertical and of circular cross-section. The soil is modelled as a linear viscoelastic layer with hysteretic material damping. A closed form solution is obtained for the resistance of the soil layer to the motion. This resistance depends on shear modulus of soil, frequency, pile slenderness, material damping and Poisson's ratio. A parametric study of the effect of these parameters is included. The soil layer resistance is expressed in a form which can be used directly in the solution of the soil-pile interaction problem which is treated in a subsequent paper. The approach also applies for rigid deeply embedded footings.     

Periglacial environment in Japan: present and past

This review article is intended to introduce periglacial environment present and past in Japan, and to summarize some studies on it. The periglacial climate in Japan is characterized by a wide annual range of air temperature and much snow accumulation in winter. This makes for local variability in appearance of periglacial processes on the mountain slopes near crests. In Japan, the main interest in periglacial studies concerns the above-mentioned variability and its causes, that is, how periglacial processes relate to vegetation, local climate especially snow accumulation and its seasonal duration, soil, micro-relief, properties of bed rock etc.Seasonal soil freezing was measured in lowlands of Hokkaido. Depth of frost penetration without snow cover increases proportionally to the increments of accumulated degree-days. Depth of frost penetration on natural conditions is affected not only by the degree-days but also by the depth of snow cover which differs locally even within a small area.The oldest frozen ground phenomena was recognized in a horizon about 50,000 years old in the lowlands of Hokkaida. Involutions about 40,000 years ago exceeded active earth hummocks in size. And the phenomena reached the maximum phase is represented by icewedge casts of the En-a pumice (ca. 15,000 abp). Most of fossil features are covered with undisturbed Ta-d pumice (cz. 9,000 abp), but earth hummocks and vertical stones have been still formed in the Holocene tephra layers.     

Measuring hydraulic permeability in a streambed using the packer test

Permeability of a streambed is an important factor regulating nutrient and oxygen availability for aquatic biota. In order to investigate the relationship, an accurate permeability should be measured. However, it is difficult to measure permeability in a coarse gravel bed using a conventional permeability test. Moreover, turbulent flow may occur in coarse bed material, and then deviations from Darcy's law do occur. Thus, permeability calculated following Darcy's law may be overestimated under turbulent flow conditions and should be corrected. The packer test can be used in highly permeable gravel beds. We developed a field method applicable to a gravel bed using the packer test and derived an equation adopting a law of turbulent flow to study the problems under any type of flow condition. The accuracy of the equation was examined using a laboratory flume with a gravel bed. The results suggested that permeability calculated from Hvorslev's equation is overestimated for turbulent flow. In contrast, our equation, developed here, could evaluate permeability accurately under any type of flow condition. Copyright © 2005 John Wiley & Sons, Ltd.