The physical properties of residual soils vary with soaking. In this paper, we have described the influence of soaking on the shear strength and pF moisture property of residual granitic soils.
The results are summarized as follows:
1) By soaking, strength parameter C_u and tan φ_u of sandy soils, such as Kitayama soil decrease to about 50% in a dry and loose condition.
2) Strength parameter C_u and tan φ_u of fine-grained soils, such as Omishima soil show a remarkable decrease, occasionally to about 20-30%.
3) The pF-moisture content curves of these soils change remarkably. Namely, capillary water and gravitational water in these soils increase greatly by soaking.
4) The decrease of the shear strength by soaking is considered to be closely related to the change of the pF moisture property.

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This paper describes the difference in soil erosion owing to the solidity of water drops.
In order to clarify the influence of the solidity (diameter and surface tension) of water drops and kinetic energy of rainfall for the quantity of splash erosion (rain-drop erosion), an experiment was performed to provide artificial rain to the soil surface. Namely, the factors concerning water drops are the diameter, surface tension and kinetic energy, the same as the 3rd part of this study. And the specimens are Kuroboku and decomposed granite (Masa soil). They consist of soft surface sparsely filled and hard surface densely filled. So, the factors concerning the soil are hardness of surface and distinction of soil.
These factors have two levels-high and low, so the number of experimental conditions are ten. In addition, the quantity of erosion is shown in the dry weight per unit area ΔW (g/cm²) and the splash depth H (the volume per unit area: mm).
The principal experimental results are as follows.
1. The order of the influence of the factors on ΔW and H was as follows.
Hardness of surface>Kinetic energy of rain>Diameter of drop>(Distinction of soil) >Surface tension
2. The relation between the two levels of a factor on ΔW and H was as follows.
1) Hard surface>Soft surface
2) High kinetic energy>Low kinetic energy
3) Large diameter (large drop) >Small diameter (small drop)
4) High surface tension (water drop) >Low surface tension (solution drop)
3. Look at from another viewpoint, the above-mentioned results were able to be expressed as follows.
1) In case of a large splash diameter, the quantity of erosion:ΔW and H increased.
2) In case of a splash of a high kinetic energy level, ΔW and _H increased.
3) Under the condition that a large impact was given to the soil surface, ΔW and H increased.
4. The results owing to the distinction of the soil was as follows.
1) Masa soil>Kuroboku on ΔW
2) Kuroboku>Masa soil on H
Therefore, it is necessary to consider the expression of quantity of soil erosion.

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This paper describes a method for estimating land use suitability according to Quantification Theory Type By this method, area suitability classification can be made without the use of an external standard.
Consideration is first directed tb the importance of area suitability classification which is indispensable for land use planning and is based on physical and non-physical properties of land for agricultural and urban use.
After making a comparison of Quantification Theory Type III with Quantification Theory Type I, the paper outlines a method for evaluating land use suitability which does not involve error from a judges' estimation. The suitability of both agricultural and urban land can also be determined by this method.
An example is given for evaluating land use suitability according to Quantification Theory Type III in Nagahama City in Shiga Prefecture. Using the classification factors in Table 1, the area suitability classification map in Fig. 1 was obtained and by which land use planning can be carried out. In the final part of the paper, some of the problems and the major characteristics of the planning stage are considered.

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In the design of fill-type dams built on pervious foundations, there is a trend toward the control of seepage by the construction of a blanket. Ordinarily, the majority of the blankets have been designed by the blanket formula of constant thickness proposed by Bennett. But when the blankets were constructed actually, many blankets had partial differences in thickness from the planned design due to the structural stability of the blankets, the resistance to the uplift, the shape of the foundation and so on.
For the above-mentioned reasons, blankets of the triangular section (an approximation of the theoretically obtained parabolic section), which Bennett indicated had the advantage of the required volume per unit width, with also a great possibility of a partial difference in the thickness from the planned design when the blankets are constructed.
Therefore, in this paper, three blankets having partly varying thicknesses on a realistic basis were analyzed, and design formulas were proposed in accordance with Bennett's way of thinking. The three blankets were one in which a part of the constant thickness varied with that of a gradual sloping upgrade toward the end where the blanket came in contact with the dam ; another in which, a part of constant thickness varied with that of a gradual sloping downgrade toward the upstream end of the blanket; and a third, in which the blanket varied its thickness by means of a step.
The accuracy of the blanket formulas proposed here were examined using the FEM analysis. As a result, it was clarified that within the limit of Eq.(3-3) in this paper, the accuracy of the proposed blanket formulas compare quite well with the accuracy of the blanket formulas of a constant thickness and parabolic section which Benett proposed.
Because the blanket formulas of a constant thickness and parabolic section have been used successfully in many practical cases, the above results indicated that the three blanket formulas proposed here could be used satisfactorily. And consideration is also given to the required length and volume per unit width of the three blankets having partly varying thicknesses.

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The reclamation works in the northwest part (1, 689 ha) of Lake Nakaumi, which is a brackish lake with an average depth of 5.4 meters, have been in progress. We have been making air temperature observations in the surrounding area for the past ten years to study the effects of largescale land draining on the air temperature conditions in the vicinity. In the present paper, the effects caused by the construction of the closing dikes around the land draining site have been discussed.
The annual mean temperature level at Station located on the shore (Fig. 1) after the construction of the dikes is about 0.5°C higher than before the construction. The levels of the pentad minimum and maximum temperatures are also found to have risen almost all the year round, but the degrees of the rise vary from season to season.
The closing dikes cut off the inflow of relatively low-temperature freshwater from the basin resulting in the a rise in the surface water temperature, which must be responsible for the rise in the air temperature of the surrounding area.

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The change in salinity distribution accompanied by drainage and drying of soil layers was investigated primarily in an experimental field (20ha in area) whose land draining was completed at the beginning of 1977. Just after this drainage, a large quantity of salt accumulated on the surface layer of the soil. Following this, desalinization advanced from the surface soil layer by the leaching action of rain. Within a period of three years, the salt became distributed in a straight line extending from an upper layer of low salinity to an under layer of high salinity. However, subsequent desalinization became stagnate, and so countermeasures for salt exclusion were examined in order to determine the necessary conditions for salinity distribution that would ensure normal growth of field crops.
1. To promote desalinization, the use of salt accumulation on the soil surface accompanied by dryness of soil layer and the leaching of that salt by rain and irrigation water were found effective.
2. To prevent the concentrated accumulation of salt in a root zone (about 0-30cm layer), the adequate improvement of the physical properties of the soil and irrigation were found to be of the utmost importance.
3. The drainage capacity of underdrain and the quantity of excluded salt were directly in proportion to each other. Based on the above findings, it was concluded that the foremost countermeasure for salt exclusion was the enhencement of the permeability of the under layer and second, the exclusion of saline percolation water and then the control of the rise of the groundwater table by the underdrain.

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In this paper, the effects of repeated loading on the moisture holding characteristics and relaxation characteristics have been investigated for the surface soil and subsoil of paddy fields. The sample soils were similar in basic physical properties, and contained aggregates amounting to about 65%. In order to discuss the effects of repeated loading, observations of the soil structure with scanning electron microscopy and stereoscopic microscopy have been carried out at varying load frequencies. The results obtained are summarized as follows:
1. In regard to the moisture holding characteristics, the pF value of the samples tended to decrease with an increase in the frequency of the loading though the water content ratio hardly changed, and the value was lower than that of the samples compacted by static loads to the same density. Again, these tendencies were more pronounced in the surface soil.
2. In regard to the relaxation characteristics, the relaxation time increased with an increase in the frequency of loading, and the time was longer than that of the samples compacted by static loads to the same density. In the range of static loads 9.8×10-2.5×10² kN/m², there was a remarkable difference in the relaxation time between the surface soil and subsoil samples.
3. Under scanning electron and stereoscopic microscopes, the aggregates from the surface soil appeared soft and loose with numerous pores with a diameter of 4-5μm, whereas those from subsoil was fairly compact with only a small amount of such type pores. The changes in the moisture holding characteristics and skeleton structure in the surface soil were more conspicuous than those in the subsoil.
The difference in the effects of repeated loading between the surface soil and subsoil (1.-2.) was almost estimated qualitatively with the photographs obtained.

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The study was performed, in the second stage of the series, to determine the salt accumulation patterns in the drying process of soil specimens saturated with NaCl solution.
The soils were Toyoura Standard Sand and Sands mixed with Kibushi Clay at 10, 20, 30% weight ratios.
Concentrations of NaCl solution ware employed at 0.05, 0.1 and 0.5%. Two hundreds cubic centimeters of soil ware placed in a glass-column 5 cm in inner diameter, so that the depth of the specimen was 10 cm. The specimens were saturated with NaCl solution and placed in the closed chamber at 40°C and 50% relative humidity. At each step of the drying process, the upper part of the specimen by 2.5cm depth from the surface was divided into five layers. On the other hand, the lower part of the specimen was divided into six layers of each 1.25 cm thickness. Thirty mill-litters of H₂O were added to the upper layers, soil and 75 ml to the lower layers soil to obtain a soil suspension. The electric conductivity of each soil suspension was measured and expressed in terms of NaCl concentration.
The following results were obtained.
1) Following preparation of the soil suspension, measurement error was found to arise from difficulties in deviding into soil layers of equal thickness. A certain correction method was used to deal with this problem. Measurement error increased with dilution of the soil suspension concentration.
2) The depth of the accumulated layers was each 5. 0 cm in the case of Standard Sand saturated with 0.1% NaCl solution, and 6.25cm with 0.5% solution. With an increase in clay content, the depth of the accumulated layers decreased, i. e., 2.5cm at a 10% clay content, 2.0cm at 20% and 1.5cm at 30%.
3) The concentration gradients of the accumulated layers showed a tendency to increase with drying, and at a fixed stage of the drying process for specimens containing a large content of clay.
4) In upper-most layer (1st layer), the concentration of salt in soil suspension (C') increased in proportion to the increase in evaporation of water from the soil surface (E). From point A to B, the salt concentration of C' still continued to increase with the higher proportional constant and then took on a constant value after point B. The in creasing vatio of proportional constant at point A took on a maximum value in the case of the Standard Sand, ane decreased with an increase in clay content.
5) The difference in C' between each of the layer deeper than the 2nd layer and-the layer which could hardly observed the salt accumulation increased in the progress of the drying process. In the extent of E where points A and B could be seen, the diff-Terence in C' decreased but increased after point B. Since NaCl accumulated in the 1st layer dispersed in the bottom layers, the indirect salt accumulation was considered to be dominant in the layers beneath the 2nd layer.
6) At point A, the water present in each accumulated layer was recorded as about.pF 1.9. No difference in water retentivity with respect to the soil texture of the specimens and concentration of NaCl solution could be found.

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The steady-state method is the most basic and reliable for measurement of unsaturated hydraulic conductivity of the various soils. But the measurement requires a lot of time and labor and is not so easy to obtain reliable and accurate values that are needed.
First in this paper, the author shows the unsaturated hydraulic conductivity of two kinds of soil measured using suction plate equipment, and then discusses the conditions (hydraulic gradient, length of columm, distance of tensiometers) needed to obtain reliable and accurate values.
Second, the drainage process toward steady-state in the soil column with upper and lower pressure boundaries is represented by a numerical solution of an unsaturated flow equation. The results are that the time required for equilibrium (to steady-state) is proportional to L²(L: length of column) when L is small and to L when L is large, and this relation is determined by the ratio |dK/dh|/(K/L).

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The authors studied the correlation between soaked, unsoaked CBR (California Bearing Ratio) and the penetration resistance of the proctor needle and have made clear that the CBR value could be estimated from the penetration resistance of the proctor needle. Soil samples of two volcanic ash soils (Tachikawa loam) and two diluvial soils from Narita formation (Table 1 and Fig. 1) compacted by the drying process were used.
The results obtained are summarized as follows;
1. The unsoaked CBR value increases with decreasing initial water content (wi) of the compacted soil. On the other hand, the soaked CBR value have the maximum value at some point of initial water content in wi-CBR relation (Fig. 2).
2. It is the point of initial water content at which the compaction curve departs from zero void curve (Figs. 2, 3 and 4). Increase in compaction energy decreases the water content where the soaked CBR has the maximum value (Figs. 3 and 4).
3. Generally, the unsoaked CBR value is larger than the soaked CBR, but at higher initial water content the soaked CBR value is larger than the other due to overcompaction (Figs. 2 and 3).
4. The relationship between the initial water content and the penetration resistance of the proctor needle is similar to wi-CBR relation, therefore the CBR value can be estimated from the penetration resistance of the proctor needle for compacted soil samples (Figs. 5 and 6).
5. According to the experimental results, we would propose the following regression equation to estimate the CBR value from the penetration resistance of proctor needle for compacted soil samples.
for unsoaked samples;
CBR=0.16 P_R+2.03 (%)
for soaked samples;
CBR=0.26P_R-1.31 (%) where P_R is the numerical value of the penetration resistance of the proctor needle (Figs. 7 and 8).

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This paper presents the work carried out in numerical study on a vertically upward water jet.
The jet flows are presently computed by the both solution procedures (the modified MAC incompressible Eulerian hydrodynamic computing technique) and the k-ε two-equation turbulence model.
The three-dimensional numerical calculations are made with a computer code called MAC 3 DTB. A flow chart of this code is given in Fig. 5.
The results are in fine agreement with the experiments in velocity profile. Illustrative examples of fully developed turbulent upward jet flows are given in Figs. 6 and 13.

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