Regarding a fine?grained soil (below 0.42mm) sampled from Iwate Prefecture, experiments were carried out for a hygroscopic-dehygroscopic process using H₂O gas and an adsorption process using N₂ gas, and its specific surface areas were calculated. Its results were classified into four groups by four factors, that is, organic matter content, clay content, clay mineral, and existence of allophane, and the differences between the results of each group were investigated.
The results are outlined as follows.
(1) The hysteresis of hygroscopic?dehygroscopic process was so great that it was suggested that a fine void of the soil has a complex structure.
(2) The much more the samples contain organic matters, the larger the difference between H₂O specific surface area and N₂ specific surface area is. As the reason for it, the increase of H₂O specific surface area was considered to be an effect due to the polarity of adsorption radical in organic matters.
(3) H₂O specific surface area after the treatment of organic matter was reduced in a sand containing a high organic matter, however, it was increased in a sand containing a low organic matter. It was considered that the reducing effect of polar radicals in the former and the removing effect of organic matters surrounding its aggregate in the latter were predominant respectively.
(4) When the correlation between the specific surface area and physical properties of soil is investigated, the existence of organic matters must be considered, especially, in an allophany soil.

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The specific surface area of soil particles with sizes of 0.42mm or less was measuredthrough N₂ gas adsorption, and calculated by the BET equation.
Then the measuring errors and the difference between the specific surfaces area of various soilsamples were compared and examined carefully. The results can be summarized as follows:
1) For the sample that weighs about 1g and that has a specific surface area of 35 m²/g or more, the relative error is estimated to be less than 5%.
2) The specific surface area of soil stabilized by urtrasomic waves is almost the same as that ofnon-stabilized soil. It is found out that the stabilization do not cause any fine soil particles to fall topieces.
3) In most cases, the specific surface area of mineral soil available from various places in IwatePrefecture ranges between 10 and 50m²/g, while in a few cases, that of pyroclastic material ex-ceeds 70m²/g.
4) The specific surface area of natural soil is almost the same as that of N₂-saturated soil. It isconcluded that the results of the measurement are not influenced by the amount of adsorbed ions.

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Formation of macropores are said to associate with live or decayed roots. There were, however, few reports which examined in details the formation of macropores and its contribution to water movement. In this paper, the formation and morphology of macropores were examined visually to study how and when macropores are made by rice roots. Their contributions to the soil water movement were also investigated. Soft X-ray, stereo microscope, soil thin section were used to observe macropores.
Following findings were obtained.
(1) Because of the pneumatic system of rice roots, water could flow into decayed and even relatively fresh rice roots. Therefore, macropores channel the water even when the central cylinders are still exist in roots. That means, for water movement, it isn't necessary that rice roots had been rotten away, it only needs falling off or eaten holes in roots by fungi or nematodes.
(2) An experiment of pot cultivation showed that macropores were made by growing of rice roots in the course of cropping period. Therefore, it can be said that macropores found in paddy soils are mostly “root created” macropores.
(3) Decayed rice roots, iron mottling and oriented or non-oriented clay particles were often seen around the edges of macropores. They were considered to contribute to conserve macropores. They may be very effective in channeling water flow through the soil. On the other hand, they don't contribute to water movement into the soil matrix due to their impervious walls.

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Sewage treatment is required for removal of nitrogen and phosphorus which is animportant problem in Japan.
This study is performed in order to develop an economical technique, which is suitable for ruralsewage treatment, for the simultaneous removal of nitrogen and phosphorus at a high rate. Theexperimental plant is like a real rural sewage facility consisting of a sequencing batch reactoractivated sludge process and was operated by submerging iron contactors.
The results are as follows:
(1) For 8 months, the treated water quality was 3.3mg/l of BOD, 4.7mg/l of SS, 1.8mg/l of T-N and 0.4mg/l of T-P on the average. The treated water was not polluted by iron.
(2) Phosphorus was removed by a combination with iron and a composition of activated sludge. Biological phosphorus removal did not work effectively, because there was no process which tookout phosphorus.
(3) Removal ability of phosphorus by iron contactors was calculated roughly at 0.45gP/m²Fe·d.

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From the structural aspect of the Complex Tank ModelMethod, the fo llowings tudies were conducted in relation to the meaning of the dividing of the block and the accuracy during an hydrological analysis.
The authors investigated theoretically the discharge mechanism of a paddy field model whichinfluences the discharge of a river.
It was clarified that the runoff discharge was influenced by the dividing of the block in a tankmodel analysis, from the consideration about the water storage in a tank model for paddy fields and the times of reuse of water in an observed field.
The authors proposed that the size of a “basic block” might be composed of Strahler streams of 2 or 3.
The authors also compared the results of computation applied Complex Tank Model Method inseveral cases by dividing the basic block into some “unit blocks” in the Houki river basin.
As a result of this study, a method was proposed for dividing the blocks from which the estimatedhydrograph in a water balance coincided with the observed one.

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The nonlinear effects on water released waves (WRWs) in channels with significantly varying cross-sections, under subcritical flow, is examined.
To describe the nonlinear effects, first the new concept of the average celerity of a kinematic wave, C, based on the quasi-uniform flow approach, is introduced, and then the relationship of discharge and average celerity of kinematic wave (Q-C curve) is obtained. Using the Q-C curve, a hypothesis is set up in which the difference of average celerity of kinematic waves between two steady flows, κ(=ΔC), represents a constant characterizing the tendency of nonlinear effects of the convective term on WRWs. This hypothesis agrees with the results of unsteady flow simulations.
It is found that the average celerity of a kinematic wave is smaller in a nonprismatic channel than in a prismatic channel, and that, in the case of an increase in discharge, nonlinear effects become smaller and even negative nonlinear effects can arise.

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Only a few attempts to investigate the effects of internal erosion processes on soil structural changes have been made so far. This study deals with the soil structural changes in artificial macropores due to internal erosion, and shows the structural changes with structural coefficients. The method of this paper is applicable for evaluating soil susceptibility to internal erosion and dispersion.
The structural coefficients were computed from the relation between the observed and calculated percolation volumes per unit time through the specimens. The calculated percolation volume per unit time was computed using the equations of Buckingham-Reiner and Darcy.
Soil mass loss of a loosely compacted sample was the most predominant of all compacted samples. The average macropore diameter of the sample increased 1.71 times more than that prior to percolation. Sufficient compaction is necessary to prevent soil structural changes due to internal erosion.
The macropore structure was observed with a polarized microscope.The observed diamter of the macropore at a depth of 3.5cm was in agreement with the calculated one. It may be concluded that structural coefficients on the basis of Buckingham-Reiner equation and Darcy equation are applicable for evaluating soil susceptibility to internal erosion and to dispersion.

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In Mokkoku irrigation reservoir the siphon pipe is very long compared with the siphon pipe in usual reservoir and the diameter of siphon pipe is longer than that of usual reservoir. There were no data to estimate the volume of air release from the water in low pressure of such a large scale siphon pipe. The model siphon pipe was used to do experiment for estimating the air release and the volume of air release was estimated by experimental result. If the velocity of the water in the siphon pipe is high the released air is carried down by flowing water. Soitisnecessary to clear by the boundary of velocity when the air would be carried out by the velocity of water for design of air removal system in siphon pipe. Through the theoretical analysis of air removal in slope pipe the relation of slope and velocity to carry the air should be clearly known.
During the experiment four kinds of pipe diameter (45, 75, 100 and 200mm) were used. The boundary of velocity in slope pipe to move the air was cleared. The experiment of air release in low pressure was carried out by using 25, 50 and 75 mm pipe diameters. The characteristics of air release under low pressure were gained. Using the experimental results the capacity of air removal system in siphon pipe of Mokkoku reservoir was designed.

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The way of water intake and the type of intake from the torrents should be suitable for torrent morphology, purpose of intake water and quantity of intake water. The bar screen compound type torrent intake which is possessed of the function both of the bar screen bottom intake type torrent intake and the bar screen back stream intake type torrent intake, is wide available. Through hydraulic model tests and observations of existing torrent intakes, in this paper, the authors clarified the hydraulic characteristics of the bar screen compound type torrent intake as follows.
(1) The intake discharge becomes larger along with increase in installation angle of the bar screen.
(2) Setting up a water cushion, we can increase the intake discharge, since back-stream along the bottom of the water cushion enters into the inlet channel in addition to direct water intake through the bar screen.In this case, intake discharge is influenced by the height of a deflector.
(3) Unit wide intake discharge is approximately 250l/s on the conditions that installation angle of the bar screen, opening of the bar screen and length of the bar are:θ=45°.ψ=15%, L₀=1m.
(4) Setting up the stop logs at the end of inlet channel, we can regulate the intake discharge and prevent from clogging of the bar screen by floating materials.
(5) Applying the formula (2), the discharge coefficient:μ can be calculated to be 0.60-0.55 against installation angle of the bar screen θ=30°, 40°, 45° and 50°.
(6) It is necessary to install the fixed weir upstream of the bar screen, in order to keep the nappe of the drop along the bar screen slope.
Moreover, the authors estimated that the bar screen compound type torrent intake can be applied to the utilization system consisted of multiple torrent intakes and reservoir.

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In the previous report, the results of a study on the uplift capacity of short piles subjected to various conditions regarding frequency and acceleration of horizontal vibration and pile length of embedment were presented. From these experiments, we concluded that the ultimate uplift capacity of piles subjected to horizontal vibrations (Q_D) was much smaller than that without any vibration. The decrease in the uplift capacity of piles subjected to horizontal vibration is closely connected with the horizontal displacement of pile's axis.
In this report, we investigated the relationship of the ultimate uplift capacity and average unit friction force for piles with different diameters (D). In addition, this report investigated the coefficient of skin friction (μ_D) and that of lateral earth pressure (K_D) for the case of D=43mm.
In these experiments, the piles whose diameters were 43mm, 66mm or 83mm with the length of embedments being from 20-40cm were set into dry sand placed at either of the two densities: medium or dense. Also, vibration characteristics controlled were two: frequency ranging from 5-20Hz and base accelerations between 50-200cm/s².
From the results, the following conclusions were drawn: The average unit friction force of piles subjected to horizontal vibration did not increase in proportion to pile diameter because of scale effect. Particularly, in the case in which the pile length of embedment was short, that tendency was remarkable. The reason why the uplift capacity average unit friction force of the piles subjected to horizontal vibration was much smaller than that without any vibration was thought to be due to the fact that the product of μ_D by K_D around the piles greatly decreased due to vibration of the piles.

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The dynamics of water and salt in a Tottori sand dune soil column and its effect on element absorption using barley (Hordeum vulgare L. cv. Daisen gold) were investigated. Three air temperatures of 25, 30 and 35°C and three ground water levels were incorporated. The results are as follows.
(1) High air temperatures and ground water level stimulated the evapotranspiration from the soil column.The former had a much stronger effect than the latter.
(2) The ground-water level affected the soil moisture profile. The lower the water level, lower was the moisture content of the soil. At the same ground-water level, similar moisture profiles were obtained irrespective of growing crops although the moisture content was higher during the growing period.
(3) Salt content ranging from 0-3 cm of the surface soil were markedly high and sharply decreased with depth. The higher the air temperature, the more salt accumulated. Soil accumulation was stimulated using growing crops.
(4) The cation accumulation in rhizosphere affected its absorption using barley. This was especially true for sodium, although barley growth was dependent on nitrogen absorption.

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We made a study of some seepage characteristics in core zone of embankment dam, taking into account of anisotropy and heterogeneity of permeability simultaneously.Firstly, we reviewed some experimental studies on these characteristics that has been carried out and emphasized the necessity of analytical study.Secondly, we formulated two-dimensional finite element analysis of seepage through a core zone considering both effects simultaneously.Lastly, we demonstrated this numerical method selecting some typical shapes of core zone (inclined and central) and parameters ρ and γ which represented anisotropy and heterogeneity of permeability, respectively. And we discussed the effects of those factors on the potential distributions, exit points and discharge (Q).
The results are summarized as follows:
1) For both of inclined and central core type, the more remarkable the anisotropy is, the higher the phreatic surface and the exit point is.The other hand, the heterogeneity has not so influence on these locations, when ρ is constant. Concerning the potential distributions, however, the flow patterns considering the heterogeneity is much different from the cases considering anisotropy only and the equipotential lines are concentrated near the bottom of downstream face.
2) Relationship between discharge and anisotropy is recognized as linear in these simulations of both core types, when ρ is constant.And when the heterogeneity becomes remarkable, the discharge decreases.The rate of decrease shows larger for1<γ<5, but becomes smaller gradually as γ increases for 5<γ<50.
3) Using the normalized discharge by Q₀ (discharge of isotropic core), relationships between Q/Q₀ and ρ are linear for each γ value in both core types.Especially in case of central core, they are plotted on the same one line for all models.Getting the values of ρ and γ, discharge of anisotropic core studied here can be simply estimated by using the presented regression equations and tables.

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In this paper, a method for reconstructing three dimensional positions of macropores, using stereofilms by the image processor, has been improved.
Firstly, the errors occurring at soft X-ray radiographies and measurements of shade positions in a pair of stereo images were estimated, which illustrate that the effect of the movement of soil samples and the correctnsess of the conjugate pair of the macropores'shade on the height of macropores from the film surface are most dominant.Also, it was shown that the movement of soil samples on the moving unit has a deflection range of 0.02mm, which is lower than the resolution of the image processing device, which is 0.15 mm.
Secondly, a system was developed so that shade patterns on the left and right film can be recognized by the image processing device, conjugate pairs of the shade elements can be properly made, and the three dimensional coordinates can be calculated.Hence, it was ascertained that the system applied to the stereo films of pseudo-soil samples making wires macropores, can calculate the three dimensional data of the left and right shades.
Lastly, applications to real samples were explained, and the directions to develop the research were presented.

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Leakage of water due to internal erosion through a dam body or foundation is one of the major troubles of fill-type dams. Recent case, histories and researches suggest that most of the internal erosion are possibly triggered by hydraulic fracturing. However, the quantitative mechanism of hydraulic fracturing still remains to be solved. Therefore, in?situ hydraulic fracture tests were carried out by a cheap, concise apparatus using bore holes dug in soft clayey volcanic soil foundation of a low earth dam (Oyachi Dam) in Niigata Prefecture.
Water was injected into the foundation through a perforated pipe under a controlled pressure and the relationship between flow rate and injection pressure was observed. It was found that a yield pressure or fracture pressure existed in all the tests. By digging the bore holes to observe the development of fracture cracks, it was also found that the cracks developed perpendicular to the bore hole periphery, which means that fracture cracks were induced by tensile stress and denies the theory that fractures are caused by shear failure. By repeating the injection test it was confirmed that once a crack is developed, it is very easily reopened by a water pressure a little higher than the earth pressure exerted on the crack.

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This study evaluates the difference in the scale effect of a shallow anchor in dry sand, by comparing the conventional model test with the elasto-plastic finite element analysis using a strain-softening constitutive model including a shear band. The conventional model tests were performed in h/B=1, 3 and 4 (h: depth, B: anchor diameter). The scale effect due to the progressive failure was observed. The progressive failure differing according to h/B and the scale effect was remarkable with an increase in h/B. For the scale effect, the conventional test was compared with the centrifugal test, and the scale effect was remarkable for conventional test in case of h/B=3, but was almost equal in case of h/B=1. In case of h/B=3, the difference in the scale effect between the conventional test and centrifugal test was due to the relative grain size effect.
Finally, it became clear that the scale effect of a shallow anchor was the result of progressive failure caused by shear banding with the scale effect being dependent on h/B.

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This flash-board is a kind of the gate system which consists of the gate board and the weight linked to the board by the wire. The system dams up the flow and the discharged water flashes down the canal course automatically. The gate board overturns by the hydrostatic pressure when the storage water surface reaches to an established level. Therefore the system is not in need any of energy to drive it. This system is used for flashing down the polluted water and the accumulated sediment in the drainage canals or the small rivers.
In this paper, the timings of the overturn and the return of the gate board are predicted. The rapidly varied unsteady flow with the surge, which occurs after the overturn of the gate board, is analyzed using the numerical method based on “MacCormack's scheme”. The numerical method is modified by the addition of second-order artificial viscosity term to the original scheme. And the efficiency of the sediment flash of the flow is estimated from the results of the movable bed experiments.

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Five different irrigation water from 200 to 2, 500μS/cm electric conductivities were prepared through diluting sea water with under ground water. They were supplied into the respective blocks of rice plant every 2 to 3 days under the condition of percolation during the irrigation season. The blocks were placed in a green house and the relations between the growth of rice plants and the irrigation water were studied. The results are as follows.
1) The rice plant in the block getting irrigation water of EC value 2, 500μS/cm was damaged just after transplant in spite of the opitimum percolation which is 17 mm per day.
2) Etiolation was observed on the plant in the block of EC value 1, 900μS/cm immediatly after mid?summer drainage. The maximum ratio of etiolation judged by the number of plant stems was around 60% at the booting stage, but after that, this phenomenon decreased gradually and disappeared at the milk ripe stage. The average percolation rate in this period was 60 mm per day, which was a good condition for desalting soil layer. This shows that the development and the function of plant root after mid-summer drainage are great factors to the control of outbreak of etiolation. On the other hand, in the blocks under EC value 1, 400μS/cm, damages did not occur and the rice plants grew smoothly.
3) The salinity desalted in the soil layer by supplied water was around 250μS/cm in EC value in the average during irrigation season, but it varied due to the percolation rate.

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Analysis on inorganic nutrient components of tomato culture solutions were conducted concerning to cyclic application of fertilizer in green house cultivation for recent three years.
The considerable relations between the daily decreasing tendency of concentrations of the nutrient components and transpiration rate were evaluated with fluctuating electric conductivity.
The obtained results were summarized as follows.
Firstly, it was clarified that the absorption degree of K⁺ by tomato plants was the largest among the other components.The electric conductivity was affected not only by the absorption degree of K⁺, but also by Ca²⁺ at the same rate.
Secondly, the direct causation was not clearly observed between the transpiration rate and absorption degree of K⁺. The Yamazaki's method for evaluating tomato's transpiration from absorption degree of K⁺ has a tendency of overestimation of transpiration rate from tomato plants.
Finally, it was pointed out that the decreasing tendency of the electric conductivity was depended on growth stages of tomato. The fluctuation of electric conductivity was affected reciprocally by the transpiration rate and absorption degree of nutrients. The mechanism, therefore, could be given by a typical equation.

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The author examined the effect of sub-soiling, with the aim of improving drainage during the growing season of upland crops, on soil physical properties for 4 years in a rotational paddy field with high soil strength and low water permeability.
In this paper, the author refers to the effect of sub-soiling and straw-mulching regarding water permeability and seedling growth of soybeans. The results are as follows:
1. After sub-soiling to a depth of 40 cm, penetration resistance at plowsole was decreased from 20 to 50 kgf/cm², to about 5 kgf/cm² and the coefficient of permeability during saturation was increased from 10^-5 to 10^-6cm/s, to 10^-3 to 10^-4cm/s.
2. After a heavy rainfall (70 mm in 2 days), the planting of soybeans was carried out, and inundation was observed in the furrows in the non-subsoiled plots, but not in sub-soiled plots.
3. Cumulative percentage of seedling growth of soybeans was only 35 to 55% in the non-subsoiled plots, but 75 to 95% sub-soiled plots. The difference was considered to be due to the difference in the draining condition for each plot. From these results, the great influence of subsoiling for improving water permeability and seedling growth of soybeans, which were planted during the rainy season in a rotational paddy field under a dry condition, could be proved.

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Some probabilistic characteristics of rainfall were analysed to make clear the relations among rainfall, drainage capacity and allowable flooding for the drainage of converted upland field. The results of the analysis were as follows.
(1) Relations between drainage capacity and maximum flooding under certain rainfalls were represented using simple water budget based on hourly rainfall and constant drainage capacity under the condition of no time lag and no water losses.
(2) Drainage capacity that was needed for a certain maximum flooding proved to be of log-normal distribution through the application of annual maximum 24-hour rainfalls.
(3) Relations between drainage capacity and maximum flooding were formulated to be Q_d=c*exp (-kS_m), where Q_d: drainage capacity, S_m: maximum flooding, and c and k: coefficients.
(4) Relations between drainage capacity and maximum flooding were also formulated based on the Talbot and the Sherman formulae of the relations between intensity and duration of rainfall.
(5) Infiltration or runoff coefficients were taken into account in simple manner for the relations between drainage capacity and maximum flooding.
(6) Several examples of Q_ds are shown with S_m=30 and 50 mm for Mito, Utsunomiya, Maebashi, Yokohama, and Choushi.

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