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

为了保证在高有机质土壤上安全施工，准确预测土壤的应力-应变特性是十分必要的。在北海道地区，这一问题很早就得到了解决，并在工程实践层面建立了一维固结沉降和稳定计算的分析方法。然而，近年来随着土地高密度利用的趋势，造成了土质沉积物侧向流动对周边工程结构的影响不容忽视的情况。本文提出了一维固结情况下和考虑土侧流情况下高有机土堆积物变形特性分析及土参数确定方法。(1)土体参数的一维固结分析与确定：提出了一种新的预测软泥炭沉积沉降时间关系的方法，取代了迄今为止采用的ROO<t>双曲曲线拟合方法。根据实验室试验结果和现场数据的统计关系，可以根据天然含水量和固结压力确定该方法所需的参数。以室内试验确定土体参数为例，表明可以采用短期加载固结试验或恒速率应变固结试验来代替标准的测土仪试验。得到了泥炭可压缩性与组成蔬菜间的定性关系。(2)基于弹塑性本构模型和土体参数确定的有限元分析：采用黏性土本构模型和反映有机土力学特性的本构模型进行了4例有限元分析，并与现场观测结果进行了对比。讨论了输入土壤参数的确定方法。从实际应用的角度来看，尽管仅根据自然含水率和现场锥贯试验数据粗略地确定了土壤参数，但计算结果与观测结果吻合较好。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