In order to establish a suitable lowland-upland cropping system in wetland rice fields, it is very important to study how to control percolation when a dry field whose plow-sole was destroyed is changed into a wetland rice field.
In this report, the author inferred mechanisms for percolation control induced by puddling and proposed an evaluation method of the effect of puddling on percolation control in a wetland rice field, whose plow-sole was destroyed, from the experimental results in laboratory. In addition, seven kinds of soil were used as the material. The results are summarized as follows:
1. Mechanism of percolation control due to puddling depend greatly on clay content in the soil.
1) In fine textured soil, it is the most important mechanism for lowering the percolation rate that the water transmission pores in the part just below the puddled layer are blockaded by clay particles.
2) In medium-textured soils to-which most of the types of soil used in the experiment belong to, the largest dry-bulk density formed at the lower part of the mixed layer played the most important role in controlling percolation.
3) In coarse-textured soil, a very clayey layer formed in the upper 0-1, 2 cm of the mixed layer mainly reduced the percolation rate.
2. Considering the experimental results for seven soils whose clay contents varied to a wide extent and estimating the largest hydraulic gradient which would appear in the paddy fields, the effect of puddling on percolation control was estimated as follows: For wetland rice field soil whose clay content is larger than 20-25%, it is possible that the percolation rate in the field, even if the plow-sole of the field was destroyed, is controlled below 20 mm/d by a careful puddling under a condition where the groundwater level is kept at about 50 cm depth.

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Lot management water requirements were intensively measured using 17 test rice-field lots in Shiga Prefecture during one or two irrigation periods. The measurements were carried out under normol rice farming water management practices.
Both of the two components of that requirement, spillage with flow-through and intended surface drainage, were separately surveyed, and its ratio to total supplied water was calculated.
According to the records, the average of the lot management water requirement was 1. 1 mm/d for irrigation period (11% of the total water supplied). Its quantity varied with the growing stage and lot, and the variation was influenced by the standard water management practices of the district to which the test lots belong, and by lot factors and farming practices.
After the character of lot management water requirement was clarified by the analysis of its actual conditions, nowadays in a planning of water requirement for an irrigation project, it is difficult to estimate that requirement separately with high accuracy.

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Available rainfall on a rice-field lot was intensively measured at 17 test lots in Shiga Prefecture over a five-year period. The available rainfall was defined as that saved in a lot from a runoff, which can be used for irrigation, so the availability means its ratio to total rainfall.
A total of 752 rainfalls were analyzed concerning availability with the water management practice. After the arrangement of these records, the following actual conditions of available rainfall were clarified.
1) The average of availability was 64% for the irrigation period, and it varied greatly with the ot and growing stage.
2) It was greatly influenced by the natural conditions of the lot, for example, the higher availability was measured in the lot with a higher soil permeability.
3) It became higher when the lot was not submerged just prior to a rainfall.
4) Generally, the upper limit of available rainfall was about 40 mm and the availability was about 80% for rainfall under 50 mm.

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Recently, large-scale development of farmland in the Shikoku area has been carried out. Even though such development has been taken during a short period, serious soil erosion still remains.Such problems occur especially during the summer monsoon season.
In this study, an investigation was undertaken to clarify the rill initiation and its development under different rainfall patterns, soil properties and topographical conditions. A discussion concerning the process of rill development and soil loss in the area investigated was also carried out.
Through cross-sectional and surface measuring approaches, rill erosion, which contributes to most of the soil erosion in the developed land area, shows a tendency to increase as the slope length increases.
It shows that the rill structure on the fields investigated has features common with the rill order which is characterized by Horton's ordering. Also, the rill distribution pattern regarding the fields is seen as being of the subdendritic type categorized by a network of channels and streams.
The rill length also increases drastically during heavy rains of the monsoon season.
As the amount of soil loss has high correlation with rill of 3 rd and 4 th order, a reasonable slope length for better soil conservation, about 30 m after this observation is recommended when the land development work is carried out.
Soil loss estimations derived from the cross-sectional profile measuring and USLE were in good agreement with each other. These two methods will be reliable for predicting soil loss in a specified period during a rainstorm.

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An approach for evaluating the effect of rural improvement policies subsidized from national coffers is presented. The integrated rural improvement work called the Model Project is selected as an example of the policies and the effect on improving the rural living environment is evaluated. The improvement levels of the living environment as of 1976 and 1983 are examined and compared for each municipality type due to the progress of the Model Project. The results demonstrate that the rise in the improvement level between these two points of time is different according to the administrative investment of the Model Project. It is concluded that the Model Project is effective for improving the rural living environment and is useful for correcting the difference in the improvement among municipalities.

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Recently, techniques for small-scale sewage treatment for rural settlements have developed in Japan.
However, there are still many unsolved problems regarding the removal of phosphorus. A new dephosphorization technique which is simple, reasonable and stable is needed.
To meet such a demand, the authors have developed a simple and highly effective phosphorus removal process by replacing the plastic contactor submerged in the tank with an iron contactor in the already developed aerating submerged contactor process.
The new experiment has been conducted in an aeration tank with submerged iron contactors to clarify the characteristics of phosphorus removal and the characteristics of iron corrosion with a concentration of dissolved oxygen.
From the results, it was discovered that a more stable rate of dephosphorization can be achieved with bacteria corrosion by sulphate reduce bacteria than with electric chemical corrosion by dissolved oxygen diffusion and the bacteria method is preferable in the aerating submerged iron contactor process.

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The basis of argument that isotropic nonliniear deformations are made by some theoretical facts and a lot of assumptions, the soils must be treated as essentially anisotropic bodies. From this viewpoint, the stress-strain relationship is verified by an independent principal stress control test.
To improve on some of the inadequacies occurring in the past, a counterbalance is set up as a prop to cancel the mass quantity of the upper-cap. And for reducing the friction of the Bellofrom-Cylinder axis, oil-less metal and teflon-coating is inserted between the cylinder and axis that is directly connected to the plate suppling intermediate principal stress.
In order to define the two coefficients of anisotropic nonlinear deformation, a test was conducted under the condition of σ₁>σ₂=σ₃ in which mean principal stress was maintained at 98, 196, 294 and 392 kN/m². Five factors (a, α, b, β, n) are fixed due to the results obtained.
Regarding the results of previous test with Toyoura Sand, one matching factor was made use for fi tting the calculation to the data. However, from the results of the calculation with five factors obtained by the present elementary test with cohesive soil, it is not nessesary to use the matching factor. And the proposal equation used for the five factors can expressed the stress-strain relationship in a uniform manner.

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In designing fill dams, one of the current major problems is how to successfully provide a contacting part for an abutment to avoid a fractured zone which is found to be large in scale in the adjacent riverbed. In other words, the problem is how to suitably cut the bedrocks and excavate a section along the axis of the dam.
This paper discusses this problem as a case study with a numerical analysis using the finite element method (FEM) and base friction model tests.
In the case in which a fractured zone has a width of 65 m at the riverbed, a base friction model test carried out and a nonlinear stress analysis performed using FEM. There have been two such cases taken up for studying bedrock excavated sections, and the contacting part is simply provided to avoid the fractured zone and to avoid the fractured zone with a step on hard rocks.
The results obtained from the aforementioned study can be summarized as follows.
1) Base rocks settle remarkably due to the fractured zone, and around the boundary of the fractured zone and the hard rocks, the stability of the dam body has a tendency to decrease.
2) When the contacting part is provided with a step on the hard rocks to avoid the fractured zone, it is desirable not be place the step on the hard rocks because tension stress induces in the hard rock under the step.
3) The base friction model tests are effective to clarify the properties of the ultimate displacement and fracture mode of the dam body.

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In this paper, an attempt is made to apply the fuzzy sets theory to seepage problems through earth structures. It is well known that the coefficient of permeability has many indeterminate components consisting of the essential indeterminacy of the soil, the experimental indeterminacy by men performing the experiments and the indeterminacy of the decision maker who determines the coefficient of permeability based on the results of experiments and his experience. Therefore, it is of practical significance to incorporate the above indeterminacy of the coefficient of permeability into the seepage analysis as the fuzzy sets. The investigation of the indeterminacy is made by a questionnaire on engineer's judgement concerning the soil measurements. It was concluded that the application of the fuzzy sets theory is a more reasonable method than using the determined coefficient of permeability.

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This paper discusses the 2-D characteristics of seepage, especially quantity of seepage under a dam with two rows of sheet-piles built on a permeable layer of finite thickness. Of two rows of sheet-piles, one is set at the heel of a dam and another at the toe. A conformal mapping technique is used for analysis.
Variables used in numerical calculation are dam width l, depth of one sheet-pile d, depth of another sheet-pile c and thickness of permeable layer e.
Applying the ratio e/l=1.0, 1. 5, 2.0, 2.5 and 3.0 with various values of ratios d/e and c/e, we obtained the quantity of seepage for 275 cases of the dam sheet-pile system.
The results obtained are as follows:(1) When the depth of one sheet-pile is shallow, the effect of another sheet-pile for suppressing the quantity of seepage clearly appears, but the deeper the depth of one sheet-pile, the more the effect of another sheet-pile for suppressing quantity of seepage decreases.
(2) In case of the sum of the depth of two rows of sheet-piles is constant, different depth of two rows of sheet-piles has more effectiveness for suppressing quantity of seepage rather than the same depth. Furthermore, the relation between thickness of the permeable layer, depth of the two rows of sheet-piles and quantity of seepage has been illustrated by a diagram.

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Mole drains were constructed at various speeds in the terraced-upland fields, which had bad drainage. The changes in cross sections of the mole drains observed after construction were discussed, regarding the rheological behaviors of the types of soils. Consequently, the construction was carried out in such a way so as to maintain the mole-drain sections as much as possible, since they were regarded as desirable for the following reasons.
Matters relating to the moling method:
1) The cross-sectional areas of the mole drains after construction tended to increase with a decrease in the construction speed. It was concluded that the lower construction speed was best for providing the most desirable construction.
2) Soil-deformation processes under construction were investigated using the Burgers model. One of the results obtained was a longer mole body which seemed best for the above-mentioned construction. Matters relating to the soil-layer conditions:
3) Suitable soil-layer conditions for mole-drain construction are shown, based on the characteristics of the soil-stress relaxation. The decrease in the rate of soil-stress relaxation in general caused by kneading, compaction and wetting of soils, was seen as best for diminishing the cross-sectional areas of mole drains after construction. Namely, kneading of the soil seemed disadvantageous for the sought after construction.
4) For the same reason, compaction of the soil seemed to be similar.
5) Increase in the soil moisture, in a like manner, seemed to be similar, too.

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An automatic valve for controlling pressure in a closed conduit system has to be able to adequately respond to the sensitivity of the flow conditions such as changing discharge and fluctuating pressure. How to set the sensitivity is very important for the stability and safetiness of a conduit system. Numerical simulations based on the theoretical model are carried for evaluating the relations between the response of an automatic control valve and the hydraulic transient phenomena in a conduit system. In addition, the phenomena and mechanism of self-excited pressure vibration are analyzed and considered.
Results are summarized as follows.
1) The dominant period of pressure variation caused by hydraulic transient phenomena is approximately the same as the fundamental period in the conduit of the upstream part of a control valve.
2) The self-excited pressure vibration in a conduit system appears when two following conditions are kept at the same time.
(1) Condition 1: The phase delay in valve response is around 1/4 the cyclic period to pressure variation in the system.
(2) Condition 2: The supplied energy due to the valve action exceeds the energy loss such as friction in the system.
3) The dual arrangement of automatic valves in series can cause severe self-excited pressure vibrations due to the interference of each valve action in a conduit system.

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When baffle-block-type stilling basins of hydraulic jump-type drops for irrigational canal were designed, drag coefficient C_D' was an important factor. The baffle blocks left one or three blocks per row in the horizontal canal and examined drag coefficient C_D' with a direct measurement of drag force among the low Froude number (Fr₁=3.0-4.5) of the forced hydraulic jump.
The results of this study can be summarized as follows:
1) The related diagram of the flow surface profile classification with parameters that cosisted of φ(=h_p/h₁, h_p=tail-water depth, h₁ initial-water depth), (B_h/h₁)/β(B_h=height of block, β=B_s/(Bω+B_s), B_s=space of each block, Bω, =wide of block), X₀/h₁ (X₀=horizontal distance from the toe of the hydraulic jump to block), were obtained.
2) Drag force P became smaller as X₀/h₁ increased. Drag coefficient C_D' became exponentially smaller as X₀/h₁ increased. The relation between drag coefficient C_D' and X₀/h₁ processed with Fr₁ with the experimented equation being obtained. And C_D'cal.(obtained by a calculation) agreed closely with the C_D'exp.(obtained by a direct measurement).
3) The relation between f (=coefficient of energyloss) and β, B_h/h₁, X₀/h₁ were obtained by the experimental equations for the number of blocks (N=1 and N=3). Generally, f tends to increase as (B_h/h₁/β on each X₀/h₁ increases and the rate of increase of f decreases as X₀/h₁ increases.
4) Tail-water depth of the hydraulic jump can be expressed by the following equation.
φ³-[{2-(1-β) (B_h/h₁) C_D'} Fr₁²+1]φ+2Fr₁²=0
The theoretical water-depth ratio derived from the equation of the tail-water depth, agreed closely with data obtained.

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The flow characteristics of the artificial large-scale roughness (bar roughness and block roughness) on a steep-slope channel were studied experimentally, with the following being obtained.
The flow over the roughness surface of a steep slope channel can be classified into tumbling flow, disturbed flow and quasi-smooth flow (each term is provisional).
The conditions of occurrence and flow characteristics of these flows were studied.
1. The conditions of occurrence of the tumbling flow were found due to the relation between the roughness arrangement (element height and spacing) and the flow properties for the cases of the bar roughness and the block roughness, respectively.
The discharge relationship of this flow was shown as a function of the overflow depth of the element at bar roughness or the overflow depth and element height at block roughness.
2. Regarding the quasi-smooth flow of the bar roughness, at first the boundary between the disturbed flow was shown as an experimental relationship related to the channel slope, element height and spacing and flow properties. The resistance of this flow was adjusted using the Knight-Macdonald's method for a mild slope bar roughness channel, that is, the tested data were regulated by resistance equation V/U_*=k log (h/χ) (where, V: mean velocity, U_*: friction velocity, h: depth of flow, χ; a parameter that depends upon the roughness states, k coefficient). The tested data were classified into 2 groups of k=6. 30 and k=10. 50, depending on the roughness state and depth. The boundary relationships of these groups were found, and then the estimate methods of χ shown for each group. All tested data agreed with the resistance equation.
3. Regarding the quasi-smooth flow of the block roughness, at first the boundary between the disturbed flow was shown as an experimental relationship, and then, the resistance of this flow. was adjusted by the same method for bar roughness. k is 5. 80 in this flow. The estimate method of χ was shown and it was shown that all tested data coincided with the resistance equation.

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