Erosion of soil by rain water flow is considered as the result of interaction between erosion and carriage of soil layer caused by spattering erosion from rain drop energy and the tractive force of water flow.
The erosion mechanism of soil grains from the soil layer that comprises cohesive soil containing fine particles, unlike the case of a moving floor of sand, is complicated by the influence of grain-size distribution, compaction, water content, content of organic matters, etc. Provided the natural contents of organic matter and water in the soil are maintained on as uniform a level as possible, the grain size distribution in the soil layer (clay ratio*), the degree of compaction (dry density), etc, are considered to constitute the principal factor for the resistance of soil layer that is closely associated with soil erosion. An experiment was conducted to investigate erosion by the tractive force of surface sheet flow, on several types of soil such as granite, volcanic ash soil and calcareous soil systems extensively distributed in western Japan after regulating the soil conditions with clay ratio* and dry density. For systematic expression of the experiment results, the dimensional quantity of qe/u*d_k, u*²/(γd/ρ) gd_k were used as the pysical indices to obtain general tendency of experiment wherein the amount of erosion is represented by qe, the friction velocity by u*, the average clod size that shows the roughness of soil layer, by d_k, the dry density by γd, the water density by ρ and gravity acceleration by g.
Through an investigation into the relationship among the tractive force of surface sheet flow, soil resistance and amount of erosion, on the basis of the above quantitative data being performed, the general susceptibility of cohesive soil to erosion, especially the amount of erosion of soil, was analyzed.

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The compacted soils used on this study were three test banks that were rolled by a tire roller. Each test bank had its own passing of roller (3, 5, 8 times). This study was aimed at clarifying the shrinkage behavior and the crack formation in three test banks.
Results are as follows:
1. All of the disturbed samples in three test banks showed the fact that shrinkage was isotropic, and all had three stages of structural shrinkage, normal shrinkage and residual shrinkage.
2. All of the disturbed samples in three test banks showed the fact that water content of the starting point in residual shrinkage coincided with plastic limit of fresh soil (PL_f).
3. All of the primary cracks in three test banks formed near the starting point in normal shrinkage. Simultaneous with forming the primary cracks of surface soils, those of subsoils formed, and the primary cracks of surface soils were combined with those of subsoils.
4. All of the secondary cracks in three test banks formed near the starting point in residual shrinkage.

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Muck soil is a type of peaty soil made up partially of decomposed organic matter, in which plants remain non discernible and is found in wet places, mixed with some minerals. The organic matter in muck soil ordinarly ranges from 20 to 50%. In lower area of the West Tsugaru district in Aomori Prefecture, however, different types of muck soil exist. The organic matter content of this soil is over 50%, with less decomposed organic matter and with sandy soil mixed in with it.
Muck soil is the main soil in the paddy fields in this area.
Generally, muck soil has high fertility because of its large organic matter content, but is too soft as a base for farmlands, making it difficult to use big agricultural machinery in the paddy fields.
Sand dressing on much soil is the most effective method to improve its texture.
To obtain the fundamental data on sand dressing, the author investigated the physical and mechanical properties of muck soils and experimented with various quantities of sand under laboratory conditions, producing the following results.
(1) The plasticity index of muck soil descend along A-line in the plasticity chart, as it changed from fresh to the air-dried condition.
(2) The compaction curves of muck soil after repeated drying and crushing changed along the zero air void curve towards soil with a lower moisture content.
(3) Both consistency limits (LL and PL) and the flow index decreased when content of sand in muck soil was increased.

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To realize successive soil moisture profiles in the presence of the roots of transpiring. plants, a macroscopic scale model was designed and a pot-experiment was conducted.
The model, assuming a quasi-steady condition of the plants and an isothermal condition, uses a macroscopic extraction term in the one-dimensional soil moisture flow equation.
It describes both moisture removal by the roots and induced moisture movement through the soil. A numerical procedure based on the finite difference solution is used to solve this model.
An experiment was conducted in a phytotron to test the validity of this model, with soybeans (Glyeine max, Merrill) raised in pots packed with Otosibe sandy loam, without the presence of a water table.
Correspondence between experimentally determined and simulated soil moisture profiles was fairly good except under a very dry condition. And the numerical solution indicates that:
(1) Soil moisture profiles are significantly affected by root density, transpiration rate, axial (=conductive) resistance and root tortousity, but negligibly affected by radial (=absorptive) resistance and evaporation rate.
(2) Extraction rate profiles gradually shift their maximum zones downward, decreasing the maxima. But the profiles for extraction rate per unit root length keep their maxima nearly constant.
(3) The water storage rate by Darcian flow is nearly negligible compared with the extraction rate.

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Natural groundwater is usually replenished by the soil moisture flow through the unsaturated zone above the water table. Therefore, when groundwater is deep, the fiow in deep unsaturated zons is very important to groundwater recharge. In this paper, the deep unsaturated ow assosiated with groundwater recharge is numerically solved in homogeneous, layer on simplied boundary conditions, using the finite element method. As a result, water content and suction profiles and the rate of groundwater recharge are obtained for unsteady one-dimensional unsaturated downward flow in a drainage process in which the water table is static and flux of the upper boundary changes from Q₁ to Q₂ (Q₁>Q₂). The properties of the flow system are realized as follows:
(1) The influence of the water table on the unsaturated flow is limited to a zone in which variation of ux is rapidly transmitted to the water table.
(2) The relation between hydrography of groundwater recherge and length of the layer L from upper boundary to water table is non-linear for small L, and approximately linear for large L.
(3) When L is large, the drinage process can be approximated by a simple equation containing only the gravity term of the flow equation, because the magnitude of the diffusion term becomes smaller than that of the gravity term.

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In an effort to obtain a better understanding of the resistance characteristics of a flow passing through a foot protection construction of a diversion weir, the effects of a submerged overflow were researched. The following facts were obtained.
1. The energy loss due to flow passing through a foot protection construction was affected by the extent to which the overflow of the weir was submerged and this energy loss was smaller than the loss of a protective device of the same construction which was set up in an open channel flow with the same discharge and depth. The difference between these energy losses increased as the flow state approached the boundary of the free and submerged overflow, and decreased with an increase in depth, with both the losses reaching the same value. It was considered that this phenomenon was due to the difference in the velocity distribution of the flow coming into the protective construction of each channel.
2. The ratio, n_r, of n_w to n₀ for the flow state is the same (where n_r=n_w/n₀, n_w is Manning's roughness coefficient for the foot protection construction of the weir, and n₀ is the roughness coefficient for the case in which the same construction is set up in an open channel flow) is related to the degree of submerged overflow, Hr and Hrc (where Hr=H₂/H₁: H₁ and H₂ are the total energy in the upstream or downstream of the weir based on the crest, respectively; and Hrc is Hr at the boundary of the free and submerged overflow of the weir).
The relationship is represented by the equation,
n_r=1-0.6001-Hr/1-Hrc.

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Dynamic behavior of soil structures with a slope, such as fill dams, may be affected by initial shear stress, because soil under a sloping surface is subjected to shear stress prior to applying dynamic stress. The purpose of this study is to determine quantitatively the effects of initial shear stress on the dynamic behavior of the materials composed of those structures.
We performed dynamic triaxial tests on saturated Toyoura Sand applying static shear stresses prior to the application of dynamic stresses. The intensity of initial shear stress is determined by the static mobilized stress ratio MSR defined as MSR=(q/p')/(q/p') fail.; in which q=δ₁'-δ₃', p'=(δ₁'+2δ₃')/3 The sinusoidal dynamic load (f=1, 2, 4 Hz) is put through 30 cycles in an undrained condition.
The test results show that shear strain and pore pressure develop in different ways from those under the isotropic stress condition:(1) Plastic shear strain significantly increases in the first 10 cycles due to the anisotropic structure of the particles incurred by applying initial shear stress;(2), The development of positive or negative pore pressure and magnitude are determined by the anisotropic structure of the particles mentioned above;(3) Shear strain amplitude varies by the degree of the anisotropic structure and the magnitude of the pore pressure. Considering of the strong dependence of shear modulus G and damping ratio D on shear strain amplitude, it can be concluded that the dynamic deformation characteristic of sand is influenced considerably by initial shear stress. These effects of initial shear stress can be determined quantitatively by four factors; the static mobilized stress ratio MSR, shear stress amplitude q_a, effective initial confining pressure p_s' and number of cycles N.

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This paper describes the results of oedometer tests, triaxial consolidation tests and consolidation tests by dead weight in tank, using soft reclaimed clay whose moisture content is fairly higher than liquid limit. It has been definitely shown by the test results that the consolidation properties of oedometer tests are almost identical with those of triaxial consolidaton tests and the relation between e and log p of consolidation by dead weight is almost equal to the extension line of that of oedometer in the range of p>0.5g/cm².
Next, it is shown that the total consolidation settlement by dead weight can be estimated using the initial moisture content and the relation between e and log p. Also, the residual settlement can be estimated using the moisture content and the relation between e and log p, or using the relation between ρt-Δt and ρt from the surveying data of settlement for a certain period of time. But, the relation between settlement and time can only be predicted using the relation between ρt-Δt and ρt from the surveying data of settlement.

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Generally, in engineering construction, soil lime stabilization is often used for sub-grade course and for the road bed. More recently, soil lime stabilization has grown more popular as a construction technique. However, the methodology for stabilization of banking slopes is not yet fully developed This paper investigates agricultural considerations as opposed to engineering research.
The authors studied this problem and have attempted to develop a suitable method for soil stabilization considering agricultual problemes.
In the experiment, the authors investigated the case of spriyed sodding on a slope treated with lime, and they conducted pot tests in order to pursue an investigation, for grass. Kanto loam soil was used and stabilized with industrial lime.
The results obtained are as follows:
1) For a 30% addition rate of lime, the pH is higher and grass growth is poor, but does grow.
2) For up to a 10% addition rate of lime, there is very little influence on grass growth.
3) Addition of superphosphates at 30% soils in addition to lime shows a notable effect.
4) When soil hardness is nearly 20 mm, grass growth is good.

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In Japan, land, zoned for agricultural use, is by law defined for agricultural land use only. At present, it is a fact that there is too much agricultural land not zoned for agriculture. Because of the lack of land use control on such agricultural land, changes of land use tend to happen when it is not zoned. This is the most important problem in land use planning in rural areas.
In this paper, we propose that zoning presents conflicts among those who have different purposes for land use, and we analyzed the reason why agricultural land not zoned appeared to be too great. The results are as follows;
(1) There are four standards for using land in the future; the standard of preserving agricultural land for agricultural products, of reserving land for urban planning, of reserving land for village planning, and of preserving the right of landowners.
(2) Mostly, the subject of the standard of preserving agricultural land for agricultural products is defeated by the subject by other conflicting standards.
(3) The strength of each standard in the conflict is greatly related to a degree of persistence in the conflicted land by the standard.
(4) The degree of persistence in the conflicted land can be estimated by the rate of the area of the conflicted land to the area of all land that has the same value as the conflicted land (including the conflicted land).
(5) In this way, we estimated the degree of persistence of each standard in 35 cases. As a result, it was shown that the standard of agricultural products was less than that of the others. Therefore, too much agricultural land was excluded from land zoned for agricultural use.

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