The Influence of Contents of the Organic Matter and Treatment with the various Electrolyte Solution on the Atterberg Limits of the Soil : Studies on Jukuka of Soil after Land Reclaimed to Paddy Fields(II)

The authors divided the reclaimed land into three kinds of field conditions; only irrigated field, chemical manure given field and chemical manure and barn yard manure given field; and planted the aquatic rice in each of them. After harvest, we sampled sub-soil from each field and made a study of the Atterberg Limits of the soil. The results are as follows. The chemical manure and barn yard manure given field showed the highest Atterberg Limits, the second was the chemical manure given field and the lowest was the only irrigated field. The contents of organic matter of soil increased in the following order: Chemical manure and barn yard field > Chemical manure field > Only irrigated field. Therefore, it is concluded that the organic matter affects the atterberg Limits. Then the authors studied how the manure, (NH4)2 SO4, KCl, affects the atterberg Limits. In this study, the atterberg Limits of sub-soil soaked in various electiolyte solutions of 1N, 1/2 N, 1/4 N, 1/8 N, and 1/16 N were determined. The atterberg Limits was controlled by the concentration of the solution and was dominantly low in the case of the high concentration

Dispersion Characteristics of Soil in the Jukuka Process : Studies on Jukuka of Soil after Land Reclaimed to Paddy Fields[I]

The authors have studied the Jukuka process from the view-points of soil physics, soil mechanics and chemistry. It is important to recognize the grain size distribution as one of the physical indices. At first we investigated the deflocculating agents and, the initial water contents of samples which dispersed the soil particles best. We used four kinds of deflocculating agents, NaOH, (NaPO3)6, HCl and NH4OH, and the samples presented here were two kinds of volcanic ash sub-soil and two kinds of non-volcanic ash sub-soil. Each of them is composed of soils before land reclaimed to paddy fields, two years later, five years later and ten years later (in case of volcanic ash sub-soil eight years later). In this mechanical analysis, we used the Hydrometer method. Therefore the results obtained are as follows. In the volcanic ash ~oil the dispersion is affected by the initial water contents comparatively and the highest dispersed soil contains about 10-15% more clay than the lowest one, as shown in Fig 1, Fig 3. Concerning Kanto loam (volcanic ash soil), HCl showed the best dispersion before land reclaimed to paddy fields, but(NaPO3)6 Showed best later, as shown in Fig 1. On the other hand in the non-volcanic ash soil the dispersion efficiency does not differ with their initial water contents, and most particles are dispersed by (NaPO3)6 and NaOH, as shown in Fig 5

Investigation of the Physical and Mechanical Characteristics of Poldered Paddy Fields in Kojima Bay(I) : On the Behavior of the Foundation of the Poldered Paddy Fields caused by the Operation of a Combine Havester

In the poldered paddy fields in Kojima Bay the behavior of the cultivated surface soil is clearly distinct from that of subsoil, and in such fields the drainage of water and salt is generally not so easy. It is very difficult to work by the machinery, because the machines cause, such difficult problems as the drain disorder and other facilities' disorders. In order to solve these problems obstructing factors must be found. So the authors have experimentally investigated the behaviors of the soils before and after the operation of a combine havester. The results of the investigation are as follows: Concerning the consistency of the soils, either surface soil or subsoil is in the unstable condition, especially the disturbance gives it a tendency easily to flow and deform : the sensitivity ratio of the soils is･ very high (that of the surface soil is 2～3 and of the subsoil is infinity). These phenomena also clearly correspond with cone penetration resistance (qc), shearing resistance (τ), cohesive force (C) and unconfined compression strength (qU). Every value of the post-condition is lower than that of pre-condition. In other words they are the phenomena of the soil softening. The authors have proved in this paper that these phenomena are due mainly to the operation of a combine havester