Yoshihiko Tanabashi

Reasonable Construction Management In Fill Loading With Vacuum Consolidation Method Based On Fem Analyses

Vacuum consolidation method (VCM) is one of the recent methods for the improvement of soft ground. This method can forcibly drain pore water, and increase ground strength by loading of the vacuum pressure. A fill loading with vacuum consolidation method (FLVCM) is considered to be able to control lateral flow and upheaval of surrounding area during the rapid fill construction. However, the behavior of this combination on the ground deformation is not fully clarified on FLVCM, fill design and site management is depending on the experienced technique. In this study, numerical simulation has been carried out by finite element method (FEM) for the quantitative evaluation of the deformation suppression effect of FLVCM on the soft grounds of ariake clay, Japan. The utility of FLVCM was confirmed from comparison with the observed and the analytical ground deformation. In addition, the numerical simulation have been carried out under the various conditions of vacuum pre- and post-loading pressures and fill speeds, and it is suggested that the reasonable construction management index can be easily obtained by the site measurement of deformation.

A Prediction Method for Landslide Occurrence by Applying Vegetation Vigour Calculated from Satellite Remote Sensing Data

本研究は, 1990年7月に発生した長崎県松浦市・石倉岳地すべりを例として, 人工衛生LANDSATデータによる植物活性を利用した解析を行い, 地すべりの進行状況と比較するとともに, 数量化理論第III類および第II類を適用した危険度評価を実施したものである。その結果, 植物活性の経時変化解析が地すべり現象の把握に効果的であり, 数量化理論による地すべりの危険度評価において, アイテムの一つに植生指標を導入することが有効であることが判明した。

A RISK EVALUATION METHOD FOR LANDSLIDE OCCURRENCE WITH QUANTIFICATION ANALYSIS

Todays increasing demand for land development can no longer leave vulnerable landslide areas untouched. Therefore, a rigorous method for this risk evaluation, if available, would be a valuable instrument for preventing landslide disasters in such development areas. Currently used conventional evaluation methods are empirical and qualitative in nature, largely depending on professional/pertinent expertise and judgement. In order to introduce some scientific rigor instead, this paper proposes a quantitative evaluation method, which (a) items from Hayashis quantification theory with regard to relevant aspects (data items) connecting landslide risks, (b) classifies these items into a few categorical groups, (c) assesses the vulnerability of landslide in these items, (d) expresses the vulnerability in terms of the distribution of these data items in the multi-dimensional Euclidian space, and (e) evaluates the vulnerability as expressed by the distance measure between the eigenvalues which are respectively and uniquely determined for each category group in this space. This quantitative method, as well as the conventional method for comparison purposes, are applied to the vulnerability evaluation for Yuya district in Yamaguchi prefecture, well-known for frequent past occurrence and high risk of landslide. A significant consistency between the two evaluation results is found, including the applicability and practicality of the proposed quantitative method.

AN ANALYSIS AND SOME DESIGN GUIDES TO PILE NET METHOD

Pile-net method has been used gradually as one of the countermeasures for the high organic soil deposits (peat and muck) in Hokkaido and for the high sensitive soft clay deposits (Ariake clay) in Kyushu, Japan.Pile-net method may be often used in the future, because of its advantages which are for example, a rapidity of construction, a facility of execution management, an arresting effect on the lateral flow and so on.However, a reasonable design guide to pile-net method has not been established untill now.This paper presents the applications of two finite element analyses previously proposed by the authors to the Ariake clay deposits used pile-net method which are subjected dead loads of testing embankments.And presented herein is a few remarks on the design guide to pile-net method, as the results of some consideration and comparisons between the observed and the calculated settlements.