This study was aimed at clarifying the optimum effective soil layer depth for field improvement in a limestone area. Three experimental areas (15m×12m) with different effective soil layer depths (40cm, 60cm and 80cm) were prepared in the same field and sugar cane was planted under conditions of irrigation and non-irrigation. After the harvesting of sugar cane, the sugar production, which was calculated by multiplying the cane weight by the sucrose content, was compared among all conditions.
As a result, the effective soil layer depth with the highest production was different for conditions of irrigation and non-irrigation. The effective soil layer depth of 80cm gave the best production in the non-irrigated condition and that of 60cm gave the best production in the irrigated condition. Therefore, we concluded that effective soil layer depth for field improvement with an irrigation system in a limestone area had better be 60cm.

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In this study, we investigated water use in 5 upland irrigation districts to estimate the influence of greenhouse ratio on capacity of farm pond and water distribution system. First, we measured the water level of farm pond and estimated the amount of hourly water distribution. Then, we calculated a (indicating the ratio of the regulating capacity to amount of the daily water distribution) and F (indicating hourly concentration of water use). The capacity of farm pond or water distribution system restrict a free water use, it is difficult to clarify the relationship between greenhouse ratio and these two indices especially during the period when water requirements were intensive. We estimated the values of a and F without restriction of free water use. The results showed a positive correlation between these two indices and greenhouse ratio. When applying the value of these two indices to the amount of maximum daily water requirement, we found that the required capacity of farm pond in open field area and greenhouse area were 20m³/ha and 40m³/ha respectively.

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This paper presents an analytical method for determination of earth pressures on retaining wall with inclined backfill. The analytical method deals with a combination of two failure straight lines and the optimum failure line is obtained by the procedure of trial and error technique applied using failure equations developed in the study. The results of the present study are compared to available rigorous active and passive earth pressures of other accepted methods in both cohesionless and cohesive soils. In cohesionless soil, it is observed that the passive earth pressure coefficient obtained from the present method is less than Coulomb's theory in all cases but greater than the logarithmic spiral method when soil friction angle is greater than 30°. The variation of earth pressures with changes of cohesion of soil by the present method shows the same trend as of the Coulomb's theory. It is also observed that the decreasing rate of active earth pressure is higher in more cohesive soil. It is concluded that the earth pressures determined by the method developed here in is less than the Coulomb's solutions but greater than other methods such as Caquot & Kerisel solutions and slice method.

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To investigate the index for the 3-D displacement measurement of landslide, the system of 3-D measurement was constructed for laboratory model test with basis of photogrammetry. The experiment simulated the landslide by raising the groundwater level at the up stream side. About 50 markers were set on the slope and 3-D displacement of slope surface was analyzed. The change in areal strain distribution was calculated and compared with the location of crack of failure. It was found that the location of increasing areal strain coincides with the location of crack and that the areal strain was important index for 3-D displacement measurement. Moreover, it was found that the change in normal direction of slope surface was a possible index to know the failure aspect. From the observation of groundwater level and failure pattern, it was seen that the discharge from cliff made newly from slope failure induced the decrease of groundwater level and the successive slope failure was stopped.

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The objective of this work was to study the accuracy of the calibration equations of the amplitude domain reflectometry (ADR) sensor, that measures volumetric soil water content (θ) and of the four electrode sensor, that measures soil solute concentration (C). Sand dune soil samples with known levels of θ and C were prepared. Then θ and C were measured using ADR and the four electrode sensors. Empirical calibration equations for each sensor were calculated. For ADR it was calculated by two methods:(i) by a constant coefficient and (ii) by a variable coefficient. For the four electrode sensor it was calculated by substituting θ calculated by these methods. Water and salt balances in weighing lysimeter were measured by the ADR and the four electrode sensors, using the constant coefficient, the variable coefficient and the traditionally used coefficient. It was found that the variable and the constant coefficients of the calibration equation, for both sensors, fitted better than the coefficient calculated by traditional method. Salt and water levels as calculated by the variable calibration coefficient were especially in good agreement with the real water and salt levels.

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In these years, red-soil erosion and runoff have led to agricultural and environmental problems in Okinawa, and models predicting erosion rate are required for the purpose of assessment on land development projects and sustainable management of farmlands. The authors carried out long-term continuous and multi-points simultaneous observations at sugarcane fields. In these studies, the Universal Soil Loss Equation (USLE) and the Water Erosion Prediction Project (WEPP) were tested to verify their applicability in predicting sediment runoff at rainfall event. The calculated sediment runoff by USLE was found to be accurate except after soil disturbance. On the other hand, the result by WEPP was accurate for almost all rainfall events. The accuracy of USLE and that of WEPP was compared by using the value of root mean square error, which has revealed that WEPP is more accurate than USLE. Moreover, methods for improvement of each model were proposed based on the comparison of the prediction with the data obtained herein.

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This paper focuses on measuring and estimating diversion lengths of capillary barriers. Under unsaturated conditions, fine overlying coarse soils cause a capillary barrier along their contacts. Diversion capacity of capillary barriers has been attracting great interest when, for example, they are applied to divert water away from contaminated subsoil regions. The diversion lengths on flat boundary slopes have been estimated based on several models. But few laboratory experiments measuring diversion lengths have been conducted. And no study tries to measure and estimate the diversion lengths on curved boundary slopes. In this study diversion lengths on flat boundary slopes are measured and compared with estimated diversion lengths. The results show that the model by Steenhuis estimate diversion lengths well. This means water entry value is important to know capillary barrier phenomena. Then capillary diversion lengths on curved slopes are measured and estimated by the way newly suggested in this study. The estimated diversion lengths on curved boundary slopes were in good agreements with measured diversion lengths.

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Compost recycling is one of the methods of watershed management to reduce pollutant load flowing to the river system. An evaluation system for compost recycling scenarios was developed for watershed water quality management in Lake Kasumigaura basin, Japan. The basin was divided into six regions, and the nitrogen effluent loads of each region were computed from the GIS database constructed from the statistical data of each city. Outflow loads to Lake Kasumigaura were calculated with a water tank model classified by land use. Four scenarios concerning compost recycling were developed, and the outflow loads to Lake Kasumigaura were predicted over 10 years. As a result, the nitrogen load reduction ratio was about 10 to 40% according to the characteristics of scenarios or regions; in the scenario of compost recycling within the entire watershed, the nitrogen load was reduced in the region of high livestock waste load, and the nitrogen load increased in the region that received compost.

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One of countermeasures of reducing loads from non-point source is the use of water purifi. cation functions of a lagoon. In this study, a water quality model was developed for the lagoon around Lake Biwa in order to estimate its water quality and examine its management to enhance purification efficiency.
This model amsists of two sub models. One of them consists of a tank model and L-Q formula, and it estimates discharge and load flowing into a lagoon. Another sub model consists of a water quantity balance model and an ecosystem model, and it evaluates water quality of the lagoon. In addition, Noda Lagoon is divided into two boxes to estimate water quality, since it is divided into two portions of short-circuit and retention.
The simulation is carried out using this water quality model to control the primary production in the case of extending the operation term of a facility of circular irrigation. As a result of extending an operation term for 20 days, it can be said that the rise of the COD concentration by primary production may be controlled.

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In this research, the concrete gravity dam by the block layer construction method that uses Portland blast-furnace slag cement is targeted. The autogenous shrinkage that has never been considered in the thermal stress analysis of the concrete gravity dam was examined. Moreover, an appropriate setting method of the analytical modeling and the air temperature in the block layer construction method was examined. As a result, the following was clarified. The autogenous shrinkage exerts a big influence on the thermal stress analysis of the concrete gravity dam. Even when the concrete gravity dam is placed by the block layer construction method, an enough analytical result is obtained by 2-dimensional plane strain analysis. The thermal stress that takes the change of the air temperature into consideration can be analyzed by using the proposed air temperature estimating model.

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Authors devised the expanded steel pipe joint characterized by the structure that utilized the ductility and the toughness of steel, and the elasticity of rubber for the purpose of improvement in the reliability of steel pipeline construction, or large construction nature. As compared with the conventional welding joint, the unevenness of an inside was large and hydraulic performance needed to be checked. Then, hydraulic experiment was conducted with the test tube of the diameter of a small sum using the new joint and the conventional welding joint, and the hydraulic performance was evaluated relatively. Moreover, while examining in the pipeline constructed with the actually new joint and verifying the result of a previous experiment, the friction factor which should be adopted in the hydraulic design of the pipeline which applied the new joint was examined. The hydraulic performance of the pipeline, which applied the new joint, was not based on direction of a joint, but it was the conventional welding steel pipeline and more than equivalent, and when using the same friction factor (C=130) as a welding steel pipeline, it turns out that it is a safety side at least.

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There has been a renewal of interesting in economic evaluation of agriculture and rural areas' multifunctional roles based on choice experiments. However it is known difficult to compare more than seven roles by choice experiments from the limit of the information processing ability of human at a time. We propose the procedure for reducing the individual roles evaluated in choice experiments by the importance degree evaluation of each role by respondents, and the application possibility is verified in Tsuchiura City, Ibaraki Prefecture. The evaluated multifunctional roles consist of preventing floods, underground water nourishment, preventing soil erosion, health recreation and serenity, preservation of biodiversity and wildlife habitats, creation of beautiful landscapes, preserving water environment, and managing organic wastes. The roles evaluated to subordinate position don't obtain statistical significance when the number of observations is insufficient. It is necessary to estimate number of observation for the main survey from results of the preliminary survey.

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The effect of rice husk ash and natural zeolite on preventing expansion due to alkali-aggregate reaction was investigated according to mortar-bar method (JIS A 1146). The changes in length of mortar bars containing rice husk ash or natural zeolite were measured at different ages up to 2. years and compared with those containing various mineral admixtures such as silica fume, fly ash and blast furnace slag. The results confirmed that the expansion caused by reactive aggregates can be controlled by adding 10 % rice husk ash or 15 % natural zeolite by weight of the total cementing material. The observed differences in the expansion behaviors among mortars with various mineral admixtures were also determined and discussed.

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