The object of mechanical analysis is to classify grain groups which compose the soil by grain size and to make clear the composition of soil by grain size. However, the previous methods of attaining this objective by separating the grain groups into single grain size. However, the previous methods of attaining this objective by separating the grain groups into single grain groups was not satisfactory both from the physical and chemical points of view and consequently, the significance of mechanical analysis has not been understood sufficiently.
The author therefore made clear the relation between the results of mechanical analysis obtained by dispersing soil grain groups uniformly and the significance of mechanical analysis.
It is believed that the defect of the previous analytical methods is that the chemical and physical operations were not sufficiently connected and that most studies were centered around chemical dispersion.
The author used supersonic wave as a new physical operation while studying the previous method and tried to establish a new dispersion method.
During this process, chiefly 1) ferric oxide, 2) the relation between ion of the dispersion medium and the electric charging property of grain, and 3) electrolyte ion were studied and a new method is indicated here.
As it will appear that the experimental method of this method is troublesome, the procedure of the experiment and calculation method of the experimental results are explained in detail.
Lastly, this new method was applied in the mechanical analysis of Kanto loam and Nishitsugaru soil, by which it was made clear that good dispersion was obtained in case of both soils and that there was no discrepancy from the results of the pepette method and the hydrometer method.

抄録全体を表示

As a result of recent development in the spray irrigation equipment and the farm machineries, agricultural land have been increased in the sand-dune regions and with this, the necessity for good farm road has begun to be realized gradually. Hence the authors constructed test roads in sanddune regions by two different methods, that is the hot-mix asphaltic concrete paved road and the emulsion macadam paved road.
Experiments have been carried out on these test roads by using several farm vehicles (wheel type and crawler type farm tractors, motor truck, etc.).
The following results were obtained from above investigation.
1) Little difference was found between the two test roads regarding the running resistance of farm vehicles.
2) A comparison of the distribution of internal stress in the roadbed under the travelling tractor wheel of the two test roads indicated that the internal stress directly under the tractor wheel of the emulsion macadam paved road was larger than that of the hot-mix asphaltic concrete paved road.
3) Damage to the road surface by truck shoes of tractor was large in case of the emulsion macadam paved road but the damage was small in case of hot-mix asphaltic concrete paved road.

抄録全体を表示

The compression of compacted partly saturated soil is divided into three parts, namely, instant compression, compression during primary consolidation and secondary consolidation In this paper, the fundamental properties of secondary consolidation are shown. The relation between volume strain ε during secondary consolidation and log t is expressed as a linear relation for a considerably long time. The shape of consolidation curve is divided into three types according as load increment ratio and the influence of secondary consolidation on the consolidation curve grows great as the load increment ratio is smaller. The value of dε/d log t during secondary consolidation is independent of the load increment ratio and some variation of dry density of soil but dependent on consolidation pressure. The secondary compression ratio grows large as the load increment ratio is smaller.

抄録全体を表示

The nature of the cracks which are developed markedly in the clayey paddy field soil will be treated in a series of three papers. In the case of the mechanized farming, it is important to accelerate the drying of the clayey paddy field soil after drainage of residual water and to increase its trafficability. In such cases, it is especially required to increase the evaporation of soil moisture from ground surface. Paying attention to the crack, which are developed markedly in clayey paddy field, experimental researches were carried out for the purpose of clarifying the effect of cracks promoting the evaporation.
In this paper, the first one in the series, a set of the drying box (30×30×20 cm, water tight) and a series of heat lump which gives a constant thermal condition of 25°C, 30°C and 40°C on soil surface, were used as a thermostatic box for the fundamental test.
The sample with the water content near the liquid limit was packed uniformly in the drying box, and was tested in several cases: the drying characteristics of clayey soil with or without crack.
These cracks were developed with shrinking of the sample in the drying box, and also with the artificial cutting in the sample.
A water tight sheet was applied to the side surface of the sample, to impede the evaporation from soil shrinkage cracks.
The experimental results are as follows;
1) When the sample are dried up only on the upper surface, its drying characteristics is divided into three or four stages. Namely, in the first stage, the rate of drying is mainly defined by its surface area and continues the constant rate till the surface soil moisture becomes about pF 2.4, and in the second stage, because of the impedimental action of interior factors of clayey soil (such as structure etc.), the rate becomes rather slow, but holds near the constant ratio till the surface soil moisture becomes pF 4. In these two stages, the relation between moisture content and elapsed time shows nearly straight line, and the diferences of these two stages are not so obvious when the applied temperature is low. In the third stage, as there is no free water in the surface soil layer, the rate of drying becomes much slow. When the whole portions of the sample are dried up to the pF 4 of soil moisture, the decrease of soil moisture becomes extremely little.
2) Being evaporated both from the upper surface and from the crack surfaces, the drying of clayey soil is so accelerated, and the aforementioned differences of the evaporation rate of the first and the second stage does not appear. It may be thought that because of the expantion of the crack width, the evaporation from the crack surface is supplied, and reduces the rate of drying related to the interior factors in the clayey soil.
3) Being 0.9-1.0 cm in width, the crack shows apparent effect on the drying of clayey soil. In the crack, drying is obvious in the upper part until 10cm depth, and the higher is the drying temperature, the greater is the effect.
For such problemes which need studying, the following paper will be noted as a mechanism of evaporation in a crack.

抄録全体を表示

The method of calculating the stable bed of a single section river seems to be almost established but there are many unsolved problems in case of double section rivers because the situation is very complicated.
Recently, with the exploitation of water resources, water intakes have been constructed or renovated in. a down stream river which has double sections. Therefore, there is an urgent necessity for a method of calculating the stable bed of the double section river.
This paper explains the calculation method of the following double section:
1. Unless the low water channel rises to the high water channel, deposition or scour occurs only in the low water channel, and the high water channel is fixed.
2. If the deposition of the low water channel progresses and the bed of the low water channel rises to the level of the high water channel, deposition takes place in the entire section including the high water channel.
3. The widths of both the high and low water channels are fixed.
The fundamental method of calculation is as follws: the equations which express the following:
1. Law of constant bed load-The bed load in a specific section must be constant.
2. Law of discharge-A specific section must discharge a given quantity.
3. Law of energy-A specified section must satisfy Bernoulli's theorem including head loss.47and the condition in which the flow profile becomes the double section are solved by simultaneous equations to obtain the unknown quantities-energy gradient, water depth and bed level of a specified section simultaneously.
It seems that the stable bed of the double section river including the part in which double section changes into single section, may be calculated consistently by this method.

抄録全体を表示

The theories of the paper (I) are applied to the downstream part of Watarase river, which is a typical double section river, and the problems of application and the results of calculations for the stable beds are discussed in detail.
Fig. 1 and Fig. 2 give the topographical outlines of the downstream of Watarase river. The part near Fujioka is an artifical river for making water from the Watarase river flow into Akama swamp, and in view of this the width of this part is very narrow. This explains how this part influences the stable beds.
Fig. 3 shows stable beds for various discharges from 500 t/s to 4, 500 t/s. This shows how the profile of flow on the stable beds and the features of the stable beds vary with discharges, and the discharge which influenced the present bed is analyzed.
Lastly, the stable beds at the planned point of intake are shown in Table 6, and a forecast is made on how the bed levels will change by floods in the future.

抄録全体を表示

We investigated the effect of underdrainage in large clayey paddy fields (Fig.1) in Niigata prefecture for three years.
We have already shown that in clayey paddy fields cracks have a great effect on underdrainage. It requires not only underainage but also landsmoothing and lengthen the period of drainage to develop cracks in puddled layers. In this district where the precipitation is high in August (Fig.3) longer period of drainage than one month is necessary to gain bearing capacity high enough for the combine harvesting. Therefore, it is necessary to start letting water fall into canals one month before the harvesting season. And for tracter cultivation in spring it is desirable to dry up paddy fields in the harvesting time because in this district it is impossible to dry them in winter (Fig.4, 5) owing to much rain and snow in that season.(Fig.3)

抄録全体を表示

The degree of drainage and drying in clayey paddy fields varies with some facters, especially with the condition of precipitation. In order to grasp these variations correctly we made a formula to calculate the degree of drying of clayey paddy fields. Constants for calculation were gained by field investigation.
This formula was used for ten years for calculating the influences of various factors such as the period of drainage, land-smoothing and underdrainage on the degree of drying, (Fig.5, 6, 7). As a result of the calculation it became obvious that the degree of drying varied much with these factors.
We consider that such a calculation is important for planning the improvement of drainage in paddy field.

抄録全体を表示

As a hollow gravity dam is a structure consisting of constituent blocks separated by transverse joints, it was considered to behave as a kind of a two dimensional structure. Thus, it is reasonable that many studies on design of hollow gravity clams have been carried out by employing the two dimensional theory or model tests.
It is planned to construct the Uchinokura hollow gravity dam at a narrow valley with steep side slopes and in such a case, some interaction of blocks takes place to generate three dimensional stress state although the hollow gravity dam is inherently a two dimensional structure.
The authors performed two dimensional and three dimensional model test, to obtain information on three dimensional behavior of the hollow gravity dam.
An investigation made on the three dimensional behavior of the hollow gravity dam according to the observations and analysis of the results of model tests is described in this paper.
The results obtained are as follows:
1. One of the features of the three dimensional behavior of the hollow gravity dam is the rotational displacement of the blocks on the side slopes in the plane perpendicular to the dam axis. This seems to be intensified as the side slopes of the valley becomes steeper.
2. Another feature is bending of the web coused by the shear force through the side part of diamond head. This couses a bending effect on each block of the dam.
3. The above two effects causes a complex torsional bending stress state in the blocks on the side slopes.
4. In a practical design, unexpected strong stress concentration will result if carefill considerations are not given in the determination of the shape of excavation line, joint treatment and the allocation of spillway or some other incidental structures.

抄録全体を表示