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

为了在高有机质土层上安全地建造工程结构，准确预测土层的应力应变特性是十分必要的。在北海道地区，这类问题早在几年前就得到了解决，并在工程实践层面上建立了一维固结沉降和稳定性计算的分析方法。然而，近年来随着土地利用的高密化趋势，沉积土的侧向流动对周围工程构筑物的影响不容忽视。本文提出了一维固结情况下和考虑侧向土流情况下高有机质土体变形特性的分析方法和土体参数的确定方法。(1)一维固结分析和土体参数的确定：一种新的…固结-时间关系预测方法提出用更多的软泥炭沉积来代替目前使用的Roo&lt；t&gt；双曲线拟合法，该方法所需的参数可以通过室内试验结果和现场数据得到的统计关系来确定与自然含水率和固结压力有关。对于通过室内试验确定土体参数的情况，可以用短期加载固结试验或恒定应变固结试验代替标准固结仪试验来获得。基于弹塑性本构模型的有限元分析及土体参数的确定：利用建立的粘性土本构模型和反映有机土力学性质的本构模型，进行了四个算例的有限元分析，并与现场观测结果进行了比较。从实用的角度来看，尽管仅根据天然含水率和现场贯入试验数据粗略地确定土性参数，但计算结果与观测值具有较好的一致性。较少

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