Disposal of incineration ash from municipal solid waste has become one of serious social problems from the standpoint of environmental preservation. In order to cope with this problem, a technique of melting incineration ash at as high temperature as thousand and hundreds degrees, and setting by rapidly cooling using water to produce slag has been developed in recent years. On the other hand, insufficiency of aggregate is serious in the construction industry. As one of countermeasures against environmental preservation and insufficiency of aggregate, this research studied whether or not it is possible to use melting slag from incineration ash from municipal solid waste as fine aggregate for concrete. As a result, the followings have been clarified
1) Slag consists of noncrystal glass, and has no latent hydraulicity. Slag hardly elutes heavy metals.
2) Slag has excellent physical and chemical properties as fine aggregate for concrete though its fineness modulus is high. Since, however, slag has slightly high specific gravity and low coefficient of water absorption, bleeding increases with concrete using slag.
3) Since aluminum particles contained in slag aggregate react with alkali in the cement, the compressive strength of concrete using the slag aggregate lowers with an increase in the amount of mixed slag. For this reason, although slag alone can be used as fine aggregate for concrete of about 20 MPa, it is difficult for high strength concrete of about 30 MPa or more, and means for restraining the expansion is necessary to further improve the quality of slag concrete.

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When a steel piston is pushed into the specimen of cohesive soil from the surface, the soil surface around the steel piston begins to swell up and a ridge circle is built there. As this range of a ridge circle is seemed to be the non elastic zone, it was intended to describe the non elastic deformation by FEM analysis. For the purpose, a stiffness matrix of joint elements applicable to the condition of the axial symmetry was induced. In the specimen of cohesive soil (elastic body) in the cylindrical vessel, a cap zone of the joint elements was assumed. Actually the cap zone shows a non elastic behavior in loading state. And by adding different initial stresses to the joint element, various patterns of surface deformation can be derived under condition of the axial symmetry. This is the theoretical method to control the pattern of surface deformation.
The experiment was carried out as follows ; the loaming soil was packed in the cylinder mold which was 30 cm in diameter and 12.5 cm high. A steel piston of 5 cm in diameter was inserted in the soil from the center of the soil surface. The surface displacement of the specimen was measured precisely by using non contactive displacement meter. The result of the measurement was in agreement with the result of the cap zone analysis, and thus the validity of the proposed method was confirmed.

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Preserving the water quality of lakes and ponds is very important as they are one of the main water sources. Therefore, comprehensive watershed management is indispensable in order to achieve the above objective which requires the precise estimation of runoff pollutant loads. The unit load method is widely used to calculate estimated runoff loads. However, this technique does not take seasonal fluctuations or the effects of irrigation into account because yearly average values are used in this method. The monthly unit load method, developed by the Ministry of Agriculture, Forests, and Fisheries, shows the monthly fluctuations and the effects of irrigation since fertilizer time or the irrigation period is taken into account. We calculated the estimated runoff load using this method and compared it with the measured runoff load. The calculated values of the fertilized month were much larger than measured values. Then, we divided the monthly amount of fertilizer by 5: 3: 2. After the above changes calculated runoff pollutant loads were very accurate. In conclusion, more accurate estimation of the amount of fertilizer used and the amount of time involved, will lead to a more accurate estimation of pollutant loads.

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Open channel flows are studied for channel beds covered wholly or partially with rigid aquatic plants. The aquatic plants for the wholly covered channel beds are simulated by cylinders of the same height and diameter covering the bottom part of channels. In the other case, the aquatic plants for the partially covered channel beds are simulated by the same kind of cylinders, set at three kinds of spacing in the near-bank region. Based on turbulence measurements in laboratory flumes with simulated aquatic plants, the turbulence structure of the flows in the vertical and lateral directions are investigated. In these experiments the aquatic plants largely affected the turbulence structure of the flow. A theoretical method can be a tool to predict the effects of the aquatic plants on the retardation of the flow.

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A systematic modeling method and an efficient flow condition analysis algorithm inlarge-scale canal networks using the Preissmann implicit scheme are proposed. The results are shown as follows.
1) The modeling is generally complicated in case of computing unsteady flows in canal networks with the Preissmann scheme. However, this problem can be simplified by means of disconnecting the looped network. This procedure means that the looped network is considered to be a branched one. The branched network is represented by an oriented graph, and the topological sort technique is applied to it in order to decide the order of computation for the efficient sweep algorithm.
2) The large-scale simultaneous linear equations derived from the Preissmann scheme are solved by a sweep algorithm for a branched network and low dimensional simultaneous linear equations. The algorithm is certified with a simple network model, which has 57 grid points for computations. The computational cost depends on the configuration of the canal network, and it decreases according as the grid points' ratio of loops to whole networks and the number of detachedcanals decrease. The proposed method is enough of practical use, because the computational cost for the simple network model is equal to Gauss method for a sparse matrix.
3) The method is applied for flow condition analysis of a large-scale canal network which has 539 grid points for computations, in low-lying paddy field basin, and the calculated values are closely consistent with the observed results. The computational cost is 5.5 times larger than the simple network model's one per the same time steps. It is suppressed, because the grid points ratio of loops to whole networks is low in comparison with the simple network model. Meanwhile, the computational cost using Gauss method increases drastically, namely, it is 90.5 times larger than the simple network model. The reason is that many non-diagonal elements of the coefficient matrix appear by the increase of canal junctions. These results indicate that the proposed method is excellent for flow condition analysis in large-scale networks using the Preissmann scheme.

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We qualitatively interpreted the typical unsaturated soil behavior under triaxial stress conditions by using the elastoplastic model for unsaturated soils proposed by Kohgo et al. which was based on the modified Cam clay model. The results of consolidation and triaxial compression tests for compacted DL clay and a mixed soil were selected as typical unsaturated behavior. In the consolidation tests, we interpreted the behavior due to increases and decreases of suction and isotropic stresses. In the triaxial compression tests for DL clay and a mixed soil under constant suctions, we discussed their shear behavior. The elastoplastic model with two suction effects; an increase of effective stresses due to suction increase and an increase in yield stress and stiffness for plastic deformation due to suction increase, could well explain the typical behavior of unsaturated soils mentioned here.

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Use of local materials is not economically justifiable but also has secondary benefits such as improved self help in developing countries. Typical application of the local material can be found in throughflow embankments constructed by using rockfill materials to reduce peak flow of flood water. In designing the throughflow dam, it is necessary to evaluate the ability of rockfill to transmit water in response to an applied flow gradient.
As the first phase of our study to develop a design procedure for the throughflow dam, onedimensional permeability tests of the rock column specimen were carried out to investigate a head loss behavior of flow through rockfill disposition. A power-type head loss equation was proposed based on a relationship between friction factor and Reynolds number, and coefficients describing the head loss equation were determined as a function of the hydraulic mean radius. One of practical features of the head loss equation proposed is that it includes a hydraulic mean radius which can characterize effects of particle size, shape and disposition of rockfill on the hydraulic behavior of flow through granular materials. Determining the hydraulic mean radius, one can predict easily flow rate through rockfill in response to the applied hydraulic gradient by using the proposed equation. A method to determine the hydraulic mean radius based on Zingg classification of rock particle shape and the published data was proposed. It was shown that the velocity in voids calculated by the head loss equation proposed agrees fairly well with the one calculated by the Wilkins' equation which has been considered as the one most commonly used in practice. Small remarks on subjects to be investigated in our study was commented lastly.

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The load-displacement diagrams of concrete, which had been produced from recycled concrete aggregate (RC) and crushed stone (NC), were determined by notched cubic specimens and wedge splitting procedures allowing for stable crack growth. From the load-displacement diagrams, the specific fracture energy and the tension softening diagram were derived. In the process to evaluate numerically the tension softening behavior the polylinear approximation analysis method based on the fictitious crack model was used. The observed differences of the mode I fracture behavior between RC and NC were analyzed and discussed. The results showed that the specific fracture energy of RC was 110J/m², which was only 70% of that of NC. The cohesive stress of RC at the lower part of the tension softening diagram was smaller than that of NC. This means that RC has a lower aggregate interlock compared with NC. Thus, this leads to a decrease in the specific fracture energy value of RC.

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At the site, when the vacuum sewer system crosses a river or irrigation canals, a apparatus needs to be installed in the system to reduce vacuum loss. In this paper, a new type of vacuum siphon apparatus is investigated using a full scale test model.
Water and air are separated at the upstream end of the apparatus ; that is, water flows with a so-called gravity siphon pipe across the river and the separated air flows in an adjacent pipe. Then water and air are mixed at the downstream end of the apparatus and flow into vacuum sewer system again.
The flow characteristics of the vacuum siphon apparatus are examined under various conditions of inflow rate and negative pressure levels in the system. The results are 1) the new vacuum siphon apparatus worked smoothly without unexpected difficulties, such as air entrapment in the siphon pipe. 2) The flow characteristics of the siphon pipe are not affected by the conditions of negative pressure levels in the vacuum sewer system. 3) The time interval of inflow to the apparatus and the surge period occurring in the siphon pipe are important time scale for the flow conditions in this apparatus. 4) The simulation model for conditions of the siphon pipe was set up and this model makes it possible to define the design factors for an actual vacuum siphon apparatus in the vacuum sewer system.

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Each irrigation district determines the time to enforce drought measures based on a comprehensive analysis of relevant information on river discharge, weather forecasts, irrigation ability etc. This action is similar to that of a living creature protecting its body from lack of water. Based on this idea, this paper clarifies the efficiency index of drought resistance of irrigation districts and regions, which is the difference between cumulative rainfall amount from start of irrigation to commencement of drought measures and the average value for the same period in the past 30 years. In addition, an inverse relation was found between the difference of the cumulative rainfall amount and the utility ratio of water resources in the respective regions.
As for factors influencing the drought in each irrigation district, the area rate of drought occurrence (damaged area/total area) tends to be high in the order of 1) large-area districts where rotational irrigation is conducted, 2) districts utilizing small ponds as major water sources, and 3) small-area districts. The cost of drought measures per unit area tends to be low in the order of 1) large-area districts, 2) districts located downstream large rivers, and 3) districts with small-area to which supplementary water was supplied from other water sources.

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To estimate the turbulent diffusion coefficient and the particle fall velocity for suspended kaolin in open channel flow, distributions of concentration were measured using image processing. This measurement is the way that a two-dimensional vertical distribution of concentration is indirectly acquired by processing the picture recorded by a commercial video. Vertical profiles of turbulent diffusion coefficient and particle fall velocity were assessed from concentration distributions obtained by the method and advection diffusion equation, and then examined on relation to turbulent characteristics of flow. As estimating two hydraulic parameters, a fuzzy linear regression model was utilized to remove local errors in the measured concentration distributions. It was seem that the fall velocity was lowered as increasing in turbulent intensity or Reynolds stress and was notably associated with the power spectrum in rather higher frequency than lower one. It was shown that the turbulent diffusion coefficient was influenced by the energy spectrum in lower wave numbers.

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In this paper, lime and slag were added to three types of soils as a stabilizer. The strength and frost heave properties of these soils were evaluated.
When the experimental water content approaches the optimum water content, the long-term strength of stabilization soil with the slag increases significantly. When the experimental water content is relatively high, the lime stabilization method is effective at increasing strength. This implies that the strength of that soil is influenced by the decrease in water content caused by the addition of stabilizers. It was found that lime stabilization could restrict frost heave. The effect of lime stabilization on frost heave was highly significant when the addition rate or curing period increased. Frost heave was proportional to the CBR. It was found that stabilized soil having a CBR of 100 could restrict frost heave ratio below 5%.

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In water pollution of closed watershed, especially in urbanized area, there is a tendency for a nitrogen or a phosphate pollutant load to increase. In this paper, annual variations of water quality T-N and T-P, were examined for long term (1975-95) by model simulation in Imbanuma basin. The model has two sab-models, the one represents a variation of runoff load and the other represents a variation of population and land uses. In the runoff load sub-model, total load quantity is determined by multiplying population or land uses area by the unit quantity. In the population and land uses sub-model, System Dynamics was applied, and outputs are calculated to yield annual variation of population and various land uses area by feed-back loops. These feed-back loops are mainly determined by interviewing responsible persons in rural offices. This sub-model's output fits the real data of population and land uses area. The total model's output fits the real data of water quality.

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Improvement of drainage is one of the most important problems in converting a paddy field into a multi-purpose one in Hokuriku Area where clay-type soils are widely distributed. Macropores, whether cracks or those made by roots, play an important role in the underdrainage of a field with clay-type soil. Underdrainage in a field is usually estimated by measuring the permeability of soils using 100 cm3 core samples. However, it is difficult to estimate changes in volume of macropores caused by seasonal wet-dry cycles or cropping system in a field. This report deals with a method of estimating the vertical distribution and seasonal changes of volume of macropores such as cracks in a field by operating the outlet of the underdrain pipe. The procedure of this method is summarized as follows: 1) Close the outlet of underdrain when rainfall is respected. 2) Measure the water level in the underdrain pipe after the rainfall ceases. 3) Open the outlet of underdrain and measure the total discharge of water from the underdrain pipe. The total discharge of water corresponds to the volume of macropores between the water level and the depth of underdrain pipe. The vertical distribution of macropores can be estimated from the results of experiments for several independent rainfall. Changes in macropores can also be estimated by comparing the results of the different sets of experiments conducted in the concerning seasons or years.

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Water requirements for non-tilled and tilled paddy fields with marshy heavy clay soil in Hachiro-gata polder were examined during second and third year non-tilled farming.
The following results were obtained:
1) To facilitate the transplantation of what; the soil surface of non-tilled paddy field should be covered initially with water and softened. The daily consumption following its introduction into non-tilled paddy fields was found to be as much as 30 mm, though 20 mm on the average. Based on the relation of daily water consumption to ponding depth and soil hardness, a method for water management to keep the soil of non-tilled paddy fields sufficiently soft was established.
2) Water requirement for non-tilled paddy fields was 15.8 mm/d in the second year and 12.6 mmjd in the third year during irrigation. Water requirement thus does not appear to increase yearly since the soil texture is marshy heavy clay called muddy sediment and the groundwater level for such fields is high. Horizontal percolation in non-tilled paddy fields was 10 mm/d in the second year and 8 mm/d in the third year. In non-tilled paddy fields, this parameter was greater than for tilled paddy fields.

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Recently, farmers are greatly troubled about the burden of the weeding of levees, and are planting ground cover plants (GCP) tentatively as one means of decreasing the amount of weeding. GCP is expected to control levee weeds and to give a better appearance to agricultural fields, but only a few cases that have succeeded in achieving these aims.
To clear up the problems regarding the spread of GCP to levees, we carried out an investigation of GCP planting areas using a questionnaire, which was delivered to each agricultural extension station. The questionnaire was made up of the following matters.
1) Position of GCP in levee's weeding means
2) Actual maintenance conditions of GCP
3) Expected functions and estimation of GCP
The results showed characteristic inclinations that appear in the early stage of GCP planting, and the expectations for conditional arrangement such as technology developments of planting were high among the answers received. From among these, we have been paid a great deal of attention to lawn grass as basic GCP for levees.

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As one means of lessening the need for weeding, ground cover plants (GCP) are as a potential way of solving this problem. Among these GCP, we have directed our attention to lawn grass. To grasp the present condition and solve the problems, we carried out an investigation using a questionnaire for areas, where lawn grass has been planted on levees.
The lawn grass was not spread out too densely, but the estimation of lawn grass is high in these planting area. Especially, the characteristic of low height and of bearing ability for trimming and stamping are greatly estimated, and the aptitude of lawn grass for levee's basic GCP could be achieved. However, the merits of lawn grass were not effective enough, and the need for technology development of planting and maintenance must be clarified too. To get steady high estimation of lawn grass as levee's GCP, we have come up with some ideas.
1) Necessity of technical standardization regarding planting and maintenance so on
2) Necessity of having a better appearance by complex planting with other GCP

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Recently, the aggravation of water environment has become a social problem. One of the main pollutants is considered the waste food oil discharged from households. Then, authors began the study to treat the oil continuously by the Thermophilic Oxic Process (TOP). The following points were derived from this study.
1) Continuation of high temperature fermentation and high decomposition rate of the waste food oil were confirmed under the conditions of appropriate BOD load and aeration.
2) But, the activity of micro-organisms was getting low, while the process was operated by putting only the oil in the apparatus for long term. Therefore, it was found to be essential for continuous operation that the rice bran or the white of egg has to be added in order to adjust C/N ratio and to supplement the lack in the nutrition.
3) As TOP is very simple in operation and autogenetic micro-organism plays an important role in the decomposition, consumption of energy is very economical. Besides, it is characterized by the less amounts of the produced liquid and sediments. Practical use of this method will be very promising.

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