Excavating the ground which consists of the marine deposits formed during Neogen and/or Quaternary period, the acid sulfate soil occasionally appears on the execution basis. As this soil includes sulfuric acid produced with the oxidation of sulfide, the growth of plants is disturbed and it becomes difficult to improve the soil by adding a stabilizer. In general, the calcic materials such as stone powder and zeolite have been employed to neutralize the acid sulfate soil from the past. Therefore, the shells which are composed mainly of a calcium carbonate can also be considered to be useful as a material for the neutralization process. We have ascertained the stabilization effect due to the using of crushed oyster shell by comparing the amount of swelling and CBR value for soil-stabilizer-shell mixture with those for soil-stabilizer mixture. Mixing crushed oyster shell into the soil, pH value of the mixture gradually shifted to neutral with elapsed time and its water content decreased immediately. Furthermore, the amount of swelling which occurred during submergence curing was extremely small for soil-stabilizer-shell mixture and CBR value of this mixture was 1.5 to 4 times larger than that of soil-stabilizer mixture. These results indicate that both surplus soil and non-industrial waste will be utilized effectively as embankment and subgrade materials at a time.
The vegetation method has been usually and widely used in order to control the erosion on slope surface. In sandy soil slopes, however, the vegitation often cannot be sufficiently carried out because in such soils, the erosion occurs within a short period after planting vegetation or seeding . Therefore, it is necessary to stabilize the slope surface temporarily until the vegitation has covered the surface .In this paper, a temporary stabilization method, in which the mixed solution of iron-salt and lime is sprayed on the slope surface, is proposed. To examine the validity of the proposed method , soml aboratory tests were carried out on sandy soils by adding the solution of iron-salt and lime mixed in various ratios.The results are summarized as follows: 1. The appropriate mixture ratio of iron-salt and lime is about 7:3. 2. The internal friction angle of soil is increased by mixing it with iron-salt and lime. 3. The strength increase is considered to be caused by the action of iron oxide as a cementing agent between the soil particles.
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