Studies on the vertical downward percolation flow water in layered soil have been considerably fully carried out by research workers hitherto.
In this paper, the authors grasped the actual state of the vertical downward percolation flow of water in layered soil in which the ground water level exists at infinite depth, and made clear the phenomenon of the flow.
-Method of experiments-The experiments were carried out by layered soils where order of stratification has six sets which are made by combination of three kinds of soils. At first, the permeability of unity layer soil which had been made from each soil was measured, then the discharge quantity of permeation flow of water in layered soils was measured.
-Result of experiments-Permeability of each soil layeres, except the least permeable layer in layered soils, does not indicate the permeability of layered soils.
The velocity of percolation flow is determined by the pressure which acts on the least permeable layer (in general its shows positive pressure), the depth of soil layer where pressure falls down to zero, and the layer's own permeability in layered soil. The results obtained shows that the theoretical values agree fairly well with the experimental ones.

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Reinforced concrete pipes which are used in construction of inverted siphons should be designed so as not to produce cracks reducing watertightness of the cylinder walls.
In this paper, a method for analyzing the state of stress in a reinforced concrete cylinder subjected to the internal bursting pressure is proposed for the case where the circumferential reinforcement in the cylinder wall is embedded in a single layer. The procedure is derived by assuming the cylinder to act as an elastic body consisting of concrete and reinforcing steel.
Some numerical computations are made to illustrate the influence of thickness of the cylinder shell and the reinforcement ratio on the state of stress in reinforced concrete cylinders under internal pressure. The results show that the magnitude of tensile stress in concrete due to internal pressure depends to a great extent on the thickness of the cylinder wall and that the amount of reinforcement does not have so much influence on the stress reduction in concrete. It is noted that the circumferential reinforcing bars are more effective to reduce stress in concrete when they are located nearer to the inner surface of the cylinder.

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Monolithic reinforced concrete pipes are sometimes used for barrels of relatively large siphons. To study the design method for such circular siphon barrels, in the previous paper, the auther dealt with the problem of the concrete cylinders with a single layer of circumferential reinforcement. In this paper, the structural analysis of reinforced concrete cylinders in which the hoop reinforcement is placed in two layers is discussed to clarify the state of stress in the cylinder walls subjected to the internal bursting pressure.
The method of computing the stress distribution in a reinforced concrete cylinder under internal pressure is developed on the assumption that the behavior of the cylinder is elastic and that the compatibility condition of the deformation of the reinforcement and the ajoining concrete layer holds. In the first instance, the tensile stress in concrete is assumed to be effective to withstand the internal bursting pressure. Further discussion is made for the case where the tensile stress in concrete is ignored. A numerical example is shown to demonstrate the application of these methods and satisfactory results are obtained.
Some calculations are made to investigate the tendencies of stress variations relating to the arrangement of hoop reinforcement in the cylinder walls.

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Formerly, paddy field agriculture in Japan has been carried out by the private concern based on a private narrow land. But nowadays, new types of agriculture such as group cultivation and joint operation were introduced into the process of modern agriculture.
In this report, the author considered on the variation of the design of land readjustment under new style agriculture, and then compared it with the result of the practical investigation.
The result is as follows: It is considered that, the design of land readjustment under joint operation should be fairly different from that of private concern based on a narrow private land. But in practice, it was found that the ploughing structure did not varied as much because of several obstacls. The obstacls may be devided into two; one of the imperfection of joint operating and mechanization, and the other is the poor accumulation of technical study.

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As the length of the longer side ot a paddy field section suitable for the rice farming of large mechanization becomes considerably long, the arable land formation of the former type having roads, irrigation water ditch and drainage parallel to the shorter side comes to have a problem of bad drainage, especially on the land of the heavy clay soil with properties of bad drainage.
When the drainage length, or the longer side of a section, becomes longer, and drain on the earth surface becomes worse, sowing and harvest work at the suitable season cannot be done, and consequently it causes lower yield of rice and lower efficiency of the machine work.
On the other hand, roads and irrigation water ditch decrease in number and therefore the area of unavailable field and construction cost decrease. From the consideration of the balance of this advantage with disadvantage, the most profitable length of longer side is determined. The author derived an equation to calculate the most profitable drainage length-χ₀, assuming that the relation between the drainage length and yield of rice, and that between the drainage length and quality of labor can be expressed in simple equations, respectively. With this equation, the author considered further how χ₀ varies with various factors such as the rice price, labor costs, the road width, width of irrigation water ditch, and construction costs, etc.

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Regarding to the arable land formation of former type, the length of the longer side of a section is equal to the drain distance of it, so in the case of large section formation which the large mechanization is suitable for, bad drainage is essentially unavoidable.
To solve this fault radically, it is necessary to consider the arable land formation where the longer side of each section has a drainage along it.-named “Drainage emphasizing type”-
But if we settle drainage along the longer side, extention of the drainage becomes large, and consequently the area of unavailable field increases and also the construction cost is high.
Moreover, because of the increase of intersection between drainage and road or irrigation water way, the construction cost increases. Then, from the consideration of the balance of such disadvantage with advantage of reformed drain, the drainage distance, or the short side length of a section can be determined.
The author derived a equation for the use of determination of the most profitable drainage length of drainage emphasizing type, and compared the profits of former type with that of drainage emphasizing type. Then he showed drainage emphasizing type has advantage in such a case where the road interval is equal. At the area where the soil is heavy clay and the drain is not good, the introduction of drainage emphasizing type must be in consideration.

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At a step shaped orange orchard of steep-slope land with inclination of 20°-30°, when the interval of each truck roads were arranged closely, the carriage of fruits and fertilizer by man power decreases, but the road construction cost increases and the number of cultivated plants decreases. Under the consideration of balance between these advantage and disadvantage, the author derived an equation to cultivate the most profitable road interval χ₀.
The value of χ₀ becomes smaller, when the price of orange becomes lower, labor cost higher, the road gradient steeper, the road width narrower, and the land gradient gentler.
But it is not necessary to consider the χ₀ value so nervously, because the influence of χ₀ on profit is relatively small. The inclination of land slope, the road gradient, influences on the profit more than the value χ₀.

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we have been studying the aggregate characteristics of granular materials of civil engineering such as soil, sand and gravel.
In this connection we give in the present report an experimental consideration to the optimum grainsize distribution which permits the most dense packing of the material. Various studies theoretical as well as experimental on the optimum grain-size distribution have suggested, as the best type, the gap grading which lacks a suitable intermediate grain-size group. On the other hand, JIS regulation provides a continuous grading, and the above mentioned distribution is not practically used at present. The reason may be found in the following:(1) complexity of the expression for the distribution proposed and (2) necessity of readjustment of the natural granularity in its application.
On experimental investigation of these points, we obtained the expression for the grain-size distribtion at the most dense packing, in terms of the void ratio efficiency (y). We further proposed an approximate expression, using the results of measurement of 2-component mixture, to determine (1) mixing ratio for each grain-size group, (2) differences of grain-sizes between different grain-size groups and (3) the minimum void ratio.
Comparison with other methods proposed shows that our method is completely applicable.
The grain-size distribution of the material of maximum size 5 mm at the time of most dense packing (corresponding to the fine aggregate in the range of concrete aggregate), as calculated by our proposed method, gives the volume ratios of 51%, 25% and 24% for the grain-size groups of 5mm, 0.9mm and 0.13mm respectively.
In general, the optimum grain-size distribution for the most dense packing seems to be devoid of 1 or 2 classes in comparison to the standard sieve for aggregate as employed in the present Japanese Industrial Standard. This tendency is also found in the calculations by other methods proposed heretofore.

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