An experimental study of aeration control was conducted by dissolved oxygen (DO) as a parameter in a Sequencing Batch Reactor (SBR). Experiments were performed by changing the rate of aeration and concentrations of MLSS and COD within the range of the experimental conditions, and subsequently investigated the degradation rate of substrate and the variation of DO concentration.
It was revealed that there are two range of aeration time which the DO level indicates a certain value (balanced DO concentration) and great rise respectively, and DO level rose quickly in large range from the so-called “balanced DO concentration” just after degradation of the substrate in the reactor was completed. Consequently this indicates that DO can be reliably used as the indicative control parameter of reaction time. On the other hand, the “balanced DO concentration” varied with changes of aeration rate and initial concentrations of MLSS and COD. Therefore it might be possible to properly control the SBR process by watching the “balanced DO concentration ” with the measurement of DO concentration.

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A flood routing model has been formulated and applied to the natural rivets flowing through the western region ofJakarta, West Jawa, where floods cause severe damages every year. The model consists of the tank model for analyzing the discharge of direct runoff due to torrential rainfall and the hydrodynamic model for routing the behavior of the flow in the river network The parameters of the tank model were calibtated based on the observed data of actual rainfall and discharge, while the hydrodynamic model was numerically solved by using Preissmann scheme. By utilizing interior boundaries, the geometry of the mountainous river channel having steep slope was approximated by a stepwise channel in order to exclude the supercritical flow. The applicability of themodel was recognized with satisfactory results in routing water surface and the model was applied for demonstrating the effectiveness of three drainage projects planned to mitigate flood disasters.

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The purpose of the cutting-off zone of gravel layer was to shut off the capillary rise of brackish water up to the top soil. The leaching efficiency had been lowered with the so called capillary barrier phenomena which occurred at the boundary between the upper top soil and the lower gravel layer when the precipitation was not enough. Here, we tested model of “inclined cutting-off zone” because the low leaching efficiency might have been brought about with the horizontal structure of the cutting-off zone. The author conducted model experiments of infiltration, NaCl saline water irrigation and leaching successively for five different inclinations from 0° to 10°. As a result, the NaCl concentration of effluent changed to the fi al values with the smaller pore volumes with the larger inclinations, ex. the pore volume needed to reach 80%-leaching was as small as 0.8 for 10 °inclination compared to 1.2 for the horizontal case. The equivalent retardation factor calculated for the breakthrough curves decreased linearly from 1.0 according to the increase of inclination.

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Samples of the surface Andosols in the Kanto Loam Formation were extracted and the structural properties of macropores and drainability were examined.
Other properties which include pF-moisture distribution curve group, characteristics of organic matter content and macropore diameter were analyzed. The soil matrix of Andosols was observed using soft X-ray radiographs
The soil was found to contain many soild particles with high density and well-developed soil aggregates. The Andosol structure had a high difference between fine and coarse macropore and tortuosity of the water flow path was small.
The study has made it clear that macropores found in Andosols, regardless of bulk density or porosity become the main course of the saturated hydraulic conductivity. However, when the natural structure of Andosol is compacted, the saturated hydraulic conductivity declines explaining the reduction in the water path and increase in tortuosity.
With the above, discussion, it was confirmed that macropore of surface undisturbed Andosols in the Kanto Loam Formation contributed in the isotropic soil structure and soil drainability.

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It has been experimentally confirmed that steady viscosity of clay suspensions usually decrease with elapsed time, but sometimes increase for a certain clay suspension. To explain this phenomenon, Moore (1959) introduced the particle structure model in suspension in which build-up and destroy of links are balanced under steady state. Then he succeeded to express time dependence of viscosity quantitatively and graphically. From his model, changes of viscosity should decrease with elapsed time, and converge on a certain value.
In this study, we examined time dependence of viscosity for kaolinite suspensions experimentally, under the various conditions of temperature and shear rate. As a result, obtained curves of viscosity as a function of elapsed time could be categolized into three types of regression formulae including Moore model. Two patterns ofcurves, except Moore model, could not be explained using Moore's supposition. It suggested that these tendenciesof experimental results are much influenced by temperature and shear rate out of estimation.

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BOD removal performance was investigated using observed data on rural sewerage facilities with a submerged biological filter under recirculation operation. It was found that the probability distribution of influent and effluent BOD in rural sewerage facilities agreed with the logarithmic normal distribution. BOD removal in an anaerobic filter tank was assumed to depend on the recirculating ratio, influent BOD concentration, and effluent SS concentration. The multiple regression equation between BOD removal and the three factors can be obtained from observed data. The predicted values of BOD removal in an anaerobic filter tank were approximately in agreement with the observed values. The deposited sludge on the bottom of an anaerobic filter tank have considerable influence on the effluent SS concentration from the anaerobic filter tank. The control of sludge thickness is effective in maintaining BOD removal efficiency in an anaerobic filter tank. The multiple regression equation between BOD removal and sludge thickness was effective in estimating the removal efficiency in an anaerobic filter tank. BOD removal in a contact aeration tank was also influenced by four factors, i.e., influent BOD concentration, hydraulic loading rates, effluent SS concentration, and effluent ATU-BOD concentration. It is possible that BOD removal in a contact aeration tank can be predicted by four factors. Effluent SS concentration from a sedimentation tank was approximately linear in the range of observed hydraulic loading rates in a contact aeration tank, so the effluent SS concentration was predicted from the hydraulic loading rates. The BOD removals in an anaerobic filter tank and contact aeration tank have limitations due to elution of accumulated biofilm in the filters.

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A settlement prediction method of soft ground is discussed in this paper. The method is based on the settlement data measured previously at the same site or the neighboring site of new construction. The prediction procedure proposed here are as follows. Firstly, the coefficients of volume compressibility and permeability are identified by inverse analysis. The analysis is limited to the one-dimensional problem here. Secondly, the identification results are modified based on the distribution of the initial void ratio, the relationship between the initial void ratio and the coefficient of volume compressibility, which were obtained from conducted consolidation tests, and the in-situ effective vertical stress. The procedure of the parameter modification has two patterns in the proposed method. The procedure pattern (1) corresponds to the case that the identified parameters are applied to the settlement prediction of the new construction in the neighboring site of the previous measurement site. The procedure pattern (2) corresponds to the case that the new construction is carried out on the same site, in which the settlement behavior was measured during the previous construction. The method is applied to the results of the laboratory model consolidation tests in this research to verify the applicability of the proposed method.

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This is a case study of the effect of the introduction of an innovative information system into a large-scale irrigation projects in Indonesia. In the case of large-scale projects, it is more difficult to get a comprehensive understanding of water management performance than it is in small-scale projects. This is one of the factors hindering efficient water management in large-scale projects. To cope with such a situation, an irrigation information system utilizing radio modems was introduced into the Way Sekampung Irrigation Project as a pilot project in Indonesia. The introduction of the irrigation information system made it possible to grasp the entire water management situation in the project, thus resulting in improved water management. The effect even extended to the raising of consciousness among the management office staff and field staff regarding efficient water management. These effects were produced as a result of realizing a more open water management through the disclosure of irrigation management information and the creation of a data feedback loop among the control office, the field offices, field staff and farmers.

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In the present study, the relationship between the parameter of the residual strength, φ_r, and the physicaland mineralogical properties of landslide soils was examined, using the data reported by the authors until now.
The relationships of φ_r with the <2μm clay content and with the plasticity index were not clear. The relationship between φ_r and the smectite content in the <420 μm soil samples was not clear in the regionof the smectite content below 20%. In contrast, the appropriate relation was obtained in the whole range between Or and the total of the contents of preferred-oriented clay minerals (smectite, vermiculite, chlorite and mica) in the <420μm soil samples. The relationship between them was expressed as a chair-shaped curve and the transitional region in which control of φ_r changed from the non-preferred-oriented minerals to the preferred-oriented clay minerals was clearly observed. It was indicated the possible estimation of φ_r from the relationship φ_r and the total contents of preferred-oriented clay minerals in the <420μm soil samples.

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The nearest-neighbor (NN) method is a non-parametric scheme of time series forecasting and is suited to large sample time series problem. In the runoff forecasting using the NN method, some past rainfall-runoff events that are the most similar to the current event are selected from past data, and then the next flow is estimated as the sample average of successive flows to these similar events. In this study, the NN method is applied to the real-time runoff forecasting with lead time of 1 day, 2 days and 3 days in the Shinano River basin and the Ishikari River basin, which both are large and heavy snow basins. After the hydrological data are devided into snowfall-snowmelting period and no snowfall period, the optimal model structures are determined for each period and each lead time and the forecasters are applied. The results show that in spite of its simplicity the accuracy of 1 day ahead forecasting is very good in both basins.

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Two types of rice husk ash were pulverized in a ball mill for 10 or 60 min and used as a partial cement replacement material in mortar. Compressive and flexural strength tests were carried out on the mortar specimens containing 10 or 20% rice husk ash by weight of the total cementing material. The 3, 7, 28 and 91-day strengths of the rice husk ash mortar were determined and compared with those of the control mortar and mortar containing silica fume, fly ash and blast furnace slag powder. The strength development of the rice husk ash mortar was similar to that of the silica fume mortar and better than that of the control mortar. The 3-day and 7-day compressive strengths of the rice husk ash mortar were significantly higher than those of the fly ash mortar and slag cement mortar.

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Hiezu, Daisen and Saihaku in Tottori Prefecture, have been practicing the field tests jointly since 1995 in order to compost the sludge produced from the three communities and recycle it to farm lands. This paddy field test in gray lowland soil is scheduled to be continued for about 10 years. The interim results gained from tests of past 4 years are summarized as follows.(I) Yields of rice and tulip increased by using the composted sludge. Gains of rice and tulip increased too.(2) Shipment rate of tulip increased with increase of quantity of the inputted compost.(3) Content of heavy metals in crop did not increase.(4) The accumulation of heavy metals in soil could not be found even 4 years after test began.

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The observational procedure is often used for difficult excavation works such as large-scale excavation, excavation with extensive depth, excavation in soft ground and excavation neighboring other structures to improve construction management. Features of the observational procedure are in respect of the optimum design change (the posteriori design) from measurement data under construction, when the uncertainty in the design before construction (the prior design) was positively recognized. However, it is difficult to judge whether it was “optimum design”, sincethe construction work is generally a single item production in the field. Therefore, there are not small cases in which the evaluation that it becomes the disturbance of the construction is received on the observational procedure. In this paper, the effectiveness in safety and economical efficiency of the observational procedure is objectively evaluated by the comparison between non-observation construction and observational procedure. The approach of expectation total cost used in the reliability design is used for the method of the evaluation of the effectiveness.

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This study was carried out to clarify the mechanism of soil moisture consumption of reclaimed agricultural land under film-cover cultivation. Since the plant and soil were screened by the tunnel or mulch film, rainfall was concentrated to the side of bare surface. Infiltration was occurred mainly in furrows and the bare plane surface outside the areas without film-cover.
Accordingly, actual soil moisture behavior and consumptive use were clarified from the soil physical condition and soil moisture situation under film-cover and bare surface outside or furrow. Investigation was for 2 years, 1991 and 1992, and crop and cultivation mode were tunnel-mulching net melon, water melon and mulching sweet potato.
Results obtained are as follows.
Though in most sites and soil layers, the soil was classified as sandy soil, however soil in some sites and layers was classified as loam. Readily available moisture was about 35-75 mm in a 0-80cm soil layer.
On the other hand, the soil moisture situation was obviously affected by the film shield to the rainfall and evaporation from soil surface. Then, consumptive use under film-cover tended to decrease from the bare outside, and soil moisture extraction pattern was different in the shallow soil layer.
Generally, consumptive use under film-cover cultivation was reduced, furthermore, it was considered that moisture supply by precipitation depended on the horizontal or diagonal redistribution mechanism from the outside to root zone under film-cover.

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Strength characteristics of undisturbed Ariake clays obtained by thin walled sampling in the inner area of Isahaya Bay were investigated based on the results of consolidated constant-volume direct shear tests and isotropically consolidated undrained triaxial compression tests. As a result, if soil samples were consolidated under the pressure 1.5 times greater than yield consolidation stresses obtained from the oedmeter tests in the direct shear test and under the pressure 3 times greater than yield consolidation stresses obtained from the isotropic consolidation tests in the triaxial compression tests, they reached to the normal consolidation condition in which the rate of strength increase and the internal.friction angle were constant.
In the normal consolidation condition, the rates of strength increase of the soil samples were near the lower limit of that (0.3-0.4) of Ariake clays, and the internal friction angles of the soil samples obtained from both the tests were nearly equal in the same elevation. And that, there were no unique relations between the rate of strength increase and the plasticity index, I_p, and between the internal friction angle and I_p, for the soil samples.

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Pressure and flow control devices are usually set at the head of each rotation block in sprinkler irrigation systems. A comprehensive approach to the hydraulic design of sprinkler irrigation systems is to deal a lateral line and a submain line in the rotation block as one unit. A sprinklel discharge variation is theoretically related to a pressure head variation. Equations of pressure head variations along the lateral line and the submain line are derived as a function of the pressure heads at upstream end, downstream end and average point for a uniform slope situation. When the sprinkler discharge variation is set as a design criterion, an allowable pressure head variation for the rotation block can be calculated. The allowable pressure head variation for the rotation block is allocated to the lateral line and the submain line. The lateral line and the submain line can then be designed to meet the allocated values of the pressure head variation by a trial-error method. The developed design method is evaluated with a design example.

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[in Japanese]

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