Collapse Potential and its Mechanism in Unsaturated Granular Soils

Abstract

コラプスを示す土は含水比に敏感で湿潤過程には体積圧縮挙動を示す．荷重作用下で湿潤する場合に締固められた土がもつコラプスポテンシャルは土木工学応用における一つの主要な関心事である．湿潤によって締固めた土が示す体積変化挙動の研究は，不飽和地盤工学において注目される最近の一トピックである．本稿では締固められた粒状土について実験的にその力学挙動を分析した結果を述べる．体積変化挙動は各種応力状態について独立に制御できる改良した三軸試験装置を用いて観測した．湿潤過程の応力径路は，コラプス性の土供試体が等方応力負荷状態で地下水位が上昇する現場を想定して選択された．全体積変化及び含水比変化を観測した．実験データから，初期状態の異なる不飽和粒状土のコラプスポテンシャルとそのメカニズムについて分析した．

Collapsible soils are moisture sensitive soils that induce volumetric compression on wetting. A major concern in utilizing compacted soil in civil engineering application is their potential to collapse when wetted under load. The investigation of wetting-induced volume change behavior of a compacted soil is one of the recent topic that has given due attention in the study of unsaturated soil mechanics. In this paper the mechanical behavior of a compacted granular soil is experimentally investigated. The behavior of volume changes are explored using a modified triaxial permeameter system where the stress state variables are independently controlled. Wetting stress paths are utilized to refelect field conditions associated with the rise in groundwater level in collapsible soil stratum under a certain constant isotropic loading. Measurments of total volume change and water content change are made. The experimental date are analyzed to investigate the collapse potential and its mechanism of unsaturated granular soils prepared at different initial conditions.