The investigation of the influence of suction history on volume change and shear strength behavior of unsaturated soil is one important topic in the study of unsaturated soil mechanics. From the view point of some geotechnical problems there is a lack of investigation on the effect of continuous wetting and drying process, (cyclic suction loading), on the mechanical behavior of unsaturated soils. In this paper a quantitative investigation of the shear strength behavior of compacted granular soils were undertaken using modified triaxial apparatus for unsaturated soil. Constant water content, and consolidated drained tests were carried out on specimen after and before undergoing cyclic suction loading. The deformation of the specimen during cyclic suction changes under an isotropic loading, and the shear strength behavior of the soil sheared before and after undergoing suction history were investigated and discussed. From the investigation, it was found that the shear strength of unsaturated soil depends not only on the magnitude of matric suction but also the suction history the soil undergoes. In addition, specimen that undergoes cyclic suction loading is found to have higher peak shear strength.

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Recently, wetlands are spotlighted, since it is playing important roles not only on regional ecosystems but also on the global environment, and rapid regional development or global warming threatens them. Akkeshi Lake-Bekanbeushi wetlands, which are located in the eastern part of Hokkaido Island, has high environmental values because they are including about 100 ha of very valuable bog which has still remained undisturbed and there are important habitats for many kinds of migrant birds. In order to keep their ecosystem sustainable, we have to precisely evaluate their values. So, this paper aimed to exact ly evaluate the natural environmental economical values of the Akkeshi-Bekannbeushi wetlands by selective-conjoint analysis, as mainly focusing on values of landscape and wild birds. Questionnaires asking the amount of willing to pay for environmental preservation were conducted to those who visited this area for sightseeing. Consequently, the economical value of ec osystems in this area turned out to be 1, 300 yen/year/person, the value of landscape and recreation is to be 2, 085 yen/year/person. Moreover, providing more information about the Akkeshi-Bekannberushi wetlands leads more amount of willing to pay of visitors.

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The variable infiltration capacity (VIC) model had been widely used for rainfall-runoff analysis since early 1970s. In this study, the VIC model was modified for the purpose of flood runoff analysis and real-time flood forecasting. The modified model has another non-linear tank model into which the direct discharge in the original VIC model is inputted as effective rainfall. Besides a percolation hole was added to the original one in order to preserve water balance during flood periods. The accuracy in calculated flood discharge by the modified model was confirmed by flood runoff analysis of the Kuroki Dam Basin in Okayama. In addition, the real-time flood forecasting system based on the modified VIC model combined with sequential state updating technique as extended Kalman filtering technique or inverse estimation technique was developed. The result of the application of the developed system to flood forecasting at the Kuroki Dam showed satisfactory performance that is comparable to that of the real-time forecasting system based on the non-linear tank model previously developed, though the result also showed the dependency of the flood forecasting accuracy on the rainfall forecasting.

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A variety of theoretical methods for sharing cost of irrigation operation and maintenance has been widely discussed while how farmers practically share the cost on the field does not gain enough attention. This study surveys how water users' groups in five small scale pumping irrigation projects in Monsoon Asia manage their irrigation facilities and levy their members, and analyzes the problems of their cost sharing methods. Results show that, in spite of the claimed use of cost sharing methods based on farm acreage or water volume, the direct cost sharing method, in which only the group members who use irrigation water in each operation session pay for the pump fuel cost, is more dominant. This method can be easily accepted because it is directly related to water use and appears to be fair. However, its weaknesses are far-outweighed because there are differences in the rate of fuel consumption per one unit of water from different hydrants. Farmers who bear relatively higher charges would abandon the system, and the projects cannot achieve the expected efficiency of government investment. A serious consideration of their cost sharing is needed.

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Evaluation of undrained shear strength (s_u) of clay by using laboratory tests usually faces serious problems due to limited data available and often large scatter caused by sample disturbance. In this paper, the value of electronic cone factor N_kt =11 was used to predict s_u of Ariake clay by electronic cone penetration testing. The filtering equation which is expressed as the function of the deformation modulus (E₅₀) and excess pore water pressure (u_d) was proposed as a simple equation to remove the s_u values those are considered to be rather disturbed. The filtered selected s_u values were compared to find fairly good agreement with the s_u predicted by the electronic cone penetration testing data. These errors were about ±20%.

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The role of clay liner placed in a waste landfill is the retardation and retention of the pollutants leached from waste. In the present paper we assessed the retention capability for bentonite-basalt soil composite potentially used as a clay liner material, using batch equilibrium and column tests, and predicted the heavy metal concentration in pore water leaching from the clay liner by numerical analysis. The relationship between the heavy metals retained and those of equilibrium concentration in soil solution was formulated by Freundlich equation, where the selectivity order of the metals was Pb>Cu>Zn>Cr. In the equilibrium sorption characteristic curve determined by the leaching column test, the heavy metals retained increased with increasing equilibrium concentration for Pb and Cr while exhibited almost constant at a whole equilibrium concentration range for Cu and Zn. The selectivity order of the heavy metal was the same as for the batch equilibrium test. The comparison of heavy metal retention determined by the batch equilibrium tests and by the leaching column tests indicated that the mass of metals retained was almost identical for Pb at a whole equilibrium concentration range while was different for Cu, Zn and Cr depending on the equilibrium concentration. The prediction of Pb concentration in pore water leaching from the clay liner indicated that the bentonite-basalt soil composite exhibits extremely high Pb attenuation capability.

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Consolidation experiments were conducted for Ca-Na bentonites with various ESP (0, 24, 100) and solution concentrations (0.1, 0.05, 0 molc/l). The compression index C_c and the coefficient of volume compressibility my were significantly higher for ESP = 100, whereas C_c and m_v were almost identical for ESP=0 and 24. The coefficient of consolidation C_c decreased for higher ESP. The C_c for ESP=100 was one-order of magnitude smaller than that for ESP=24. The hydraulic conductivity k decreased exponentially as the porosity n decreased. The k for ESP=24 was slightly smaller than that for ESP=0, while k for ESP=100 was two to three orders of magnitude smaller than that for ESP=24. Observed consolidation behavior did not depend on solution concentrations. Although ESP>15 is conventionally used to define a sodic soil, the results for ESP=24 were close to those for ESP=0. The soil matrix of the betonite during the consolidation changed on a larger scale compared to a clay micro-structure which could be easily influenced by soil solution concentrations and ESP.

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Animal wastes have been stored in unlined storage ponds. One concern is that nitrogen loads accumulated in soils would affect long-term water quality. At the A10 area in the Lake Kasumigaura basin, Japan, where pig production ranked high, field investigations were conducted in 1992 and 2002. Water quality and discharge in four sub-catchments were measured in detail. The nitrogen pollutant load was calculated using the unit pollutant load; the nitrogen effluent load was calculated using load-discharge regression curve. Consequently, in the sub-catchment, where pig production was ceased in 1990, nitrogen effluent loads from the retired unlined storage pond were 1.34×10₃kg·y^-1 (nitrate nitrogen load) for 1992 and 95kg·y^-1 (T-N load) for 2002. The effluent loads decreased 5% in terms of T-N load over 10 years. Furthermore, the calculated effluent rates in the sub-catchments, where pig production is performed currently, were approximately 40% for 1992 and 30% for 2002.

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In order to take fresh water from a tide river, it is necessary to clearly understand the salinity intrusion, which periodically changes according to the river discharge, tidal fluctuation and density difference. In this study, a new model having multilayer structure was developed to simulate the salinity intrusion phenomena. The model is aiming at calculating flow simply and shortly by employing new calculation techniques for vertical mixing and for boundary calculation at the river mouth. In addition to such techniques, density equivalent method was developed. In the method, thickness of each layer is changed, while density of each layer is kept unchanged in order to show the vertical density distribution. Based on such calculation ideas, the model is capable of simulating various mixing patterns caused by interaction of tide and fresh water flow. Field measurements were also carried out in the Tama River to examine the performance of the model. It was confirmed that the model could simulate the density current with enough accuracy through the comparison of numerical and observed results.

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Effectiveness of newly designed viscometer which is composed of two mescylinders connected with a long spiral capillary was tested if this apparatus can be applied to the analysis the relation between weak surface forces and flow properties of dilute clay suspension. In the apparatus, the difference of water levels in the two cylinders is measured as a function of time. This setup realizes the analysis of viscosity and non-Newtonian behavior of dilute clay suspension with solid volume fraction as small as 5.0×10^-4. The pressure-gradient in the viscomerter can be adjusted 1/1000 times lower than that of conventional one. The validity of this apparatus was confirmed using distilled water and NaCl solution. The confirmed method was applied to the analysis of flow properties of dilute suspension of montmorillonite saturated Na and Ca ions. In the case of Na-montmorillonite suspension at pH6, critical coagulation concentration which is detected as immediate increase of viscosity turned to be lower than the case at pH10. This result was interpreted as edge-face interaction. On dispersed state of Na-montmorillonite suspension, viscosity increased slightly as Na concentration decreased. This result was interpreted as electroviscosity effect. In the case of Ca-montmorillonite suspension under coagulated condition, the changes of viscosity against Ca concentration was different on each pH. Camontmorillonite suspension flowed more smoothly than that of Na-type when the suspension is coagulated. In each case, viscosity increased with the decrease of pressure-gradient.

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Hydraulic design method of curved pipe bend flow meter with bypass was shown in previous paper (Yuan, B. 1 et al., 2003).
In this paper, the development of curved pipe bend flow meter using a float meter in bypass route was shown. Recently, the mulch is introduced to prevent the infiltration of rainfall in order to control the soil moisture in the orange orchard.
Under the mulch, drip irrigation systems were carried out in orange orchard. By the introducing the flow meter, control of the irrigation system is easy. Especially if the float meter is installed at the beginning of drip irrigation system, controlling of the irrigation system is very easy.
The result is as follows.
1) The flow meter with float in bypass route is recommended to control the irrigation system and is low cost system.
2) The hydraulic design method of flow meter with bypass is proposed.
3) As curved pipe bend with bypass is used, the cost of flow meter is low and easy to set up in irrigation system.
Although main flow direction is horizontal, using the bypass flow system, float meter is easy introduced.

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Up to now, the reuse of demolished concrete is limited into the use for the foundation of structure or sub-base coarse of pavement. From the point of essential effective use of resources, however, it is necessary to compose the cascade process of utilization system for the purpose of applying the characteristics of material itself Inthis research, the new utilization of demolished concrete as the water purification material is investigated experimentally. Focused pollutant is phosphate ion in environmental water. Demolished concrete was crashed and divided into coarse particles and fine particles, and phosphate removal ability of these particles was examined with column method passing through an aqueous phosphate solution. As a result, it was confirmed that concrete particleshad the phosphate removal ability, and its mechanism of removal was assured to be the crystallization due to the calcium ion dissolved from concrete. Furthermore, removal ability of fine particles was about 8 times higher than that of coarse particles. Therefore, it was confirmed that demolished concrete is able to use for water purification material.

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The influences of rice husk ash (RHA) used as a partial cement replacement material on the durability of concrete and mortar were studied and reported in this paper. The properties of the RHA concrete, such as carbonation, freeze thaw durability, drying shrinkage, compressive strength development, resistance of steel corrosion to chloride ion penetration, and resistance to acid attack were determined and compared to those of the control concrete without RHA. The results indicated that the RHA in concrete increased the carbonation depth of the concrete with increasing the RHA content, while it improved the resistance to acid attack of the RHA mortar immersed in a sulfuric acid solution. The observed differences between the control and RHA concrete also showed that the RI-1A in concrete was effective in the strength development and the improvement of the durability of concrete.

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The purpose of this paper is to assess the transferability benefits from the rural community sewerage improvement project. We analyze the multifunctional effects of agriculture, sewerage system, sanitary equipments, water environment improvement in rural domain and water environment improvement in public domain by contingent valuation method (CVM).The main fmdings of the analysis are listed below: 1) benefit functions of 4 effects, sewerage system, sanitary equipments, water environment improvement in rural domain and water environment improvement in public domain are transferable. 2) benefit values of 3 effects, sewerage system, sanitary equipments and water environment improvement in rural domain are transferable.

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Hydrological variables in an experimental watershed (A=19.45 km²) set up in a snowy mountain region have been observed and measured in detail from Sep. 2000. In this paper we discuss and evaluate the effect of different snow cover conditions such as snow water equivalent (SWE) on the hydrological cycle by using these observed records and hydrological information estimated with a snowmelt model. The results of this study indicate that the ratioof discharge during the cold season (Dec. to May) to precipitation is about 90% every water year without beingaffected by the amount of precipitation during the cold season. It is also presented that the ratio of total snowmelt discharge during cold season to annual discharge is 50 to 57%, and this large ratio means snowpack and snowmelt playan important role in river recharge. Indicators of snow cover condition such as maximum SWE and starting date for snowmelt season are correlated with the occurrence of droughty events. Additionally, the validity of an improved temperature index snowmelt model is shown.

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To clarify the impacts on tide and tidal current in Ariake Bay by the dyke of the Isahaya Reclamation Project, it have been carried for investigating with using two approaches:(1) by analysis of observational data at tide stations and (2) by three-dimensional numerical model. Model output indicate that the 0.8-1.5% decrease of the spring tidal range in outside area of Isahaya Bay is caused by the Isahaya dyke. On the other hand, it is found that there areno changes on tidal conditions in Ariake Bay due to the Isahaya Reclamation Project from consideration on observational data. Although the about 5% decrease of tidal currents off shore of Shimabara peninsula is assumed to be influenced by the Isahaya dyke according to the results from three-dimensional numerical analysis, it is confirmed that tidal currents in outside area of Isahaya Bay illustrates no difference due to the Isahaya Reclamation Project from comparison of observational data before and after construction of Isahaya reclamation dyke; that is, tidal currents in Ariake Bay depend on observation points or water depth. Therefore, it is concluded that tide and tidal current in Ariake Bay is not primarily affected by the dyke of the Isahaya Reclamation Project.

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