Prediction of Deformation Behavior of Highly Organic Soil Deposits and Determination of Design Parameters

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In order to constuct engineering structures safely on the highly organic soil deposits, it is essntial to predict exact stress-strain behavior of the soil deposits. In Hokkaido area, this kind of problem has been tackled since early years and the analysing method for one-dimensional consolidation settlement and stability calculations have been established in the practicing engineering level. However, the situation where the influence of lateral flow of the soil deposits on the surrounding engineering structures cannot be ignored has recently been caused with the trend of high density land use.In this study, the method of analysis of deformation behavior of highly organic soil deposits and determination of soil parameters for one-dimensional consolidation case and for the case when the lateral soil flow should be taken into account were proposed.(1) One-dimensional consolidation analysis and determination of soil parameters :A new method of prediction for settliment-time relationship of … More soft peaty deposits was proposed in place of ROO<t> hyperbolic curve fitting method which has been used up to the present.Parametes required for this method can be determined with natural water content and consolidation pressure by using the statistical relationships obtained from laboratory test results and field data. For the case of determining soil parameters by laboratory test, it was shown that they can be obtained by short term loading consolidation test or constant rate of strain consolidation test in stead of standard oedometer test. Qualitative relationships between compressibility and composing vegetables of peat were also obtained.(2) Finite element analysis based on the elasto-plastic constitutive model and determination of soil parameters :Four cases of finite element analysis were perromed using the constitutive model developed for cohesive soil and that developed reflecting the mechanical properties of organic soil, and the results were compared with field observation. Method of determination of input soil parametes was also discussed.From a practical point of view, fairly good agreement between calculation and observation was obtaine in spite of crude determination of soil parameters based on the natural water content and field cone penetration test data only. Less