Microscopic investigation on the physical and mechanical meanings of liquid limit tests on clayy soils.

点击翻译按钮获取中文摘要

Liquid limit (LL) is defined as the water content in which the soil ceases to flow easily like a liquid and becomes plastic. The two alternative liquid limit tests are standardized in general. One is the Casagrande test which is popular in Japan and the U.S.A., and the other is the fall cone test spread in Europe. The purpose of this study is to experimentally examine the mechanical characteristics of both two tests and investigate their physical meanings from microscopic view point on clay-water system.Two typical clay minerals ; montmorillonite (M) and kaolinite (K) were adopted and their mixture samples were tested according to both standards. In case of K=100% sample, LL values from both tests almost agreed as 30.2%. In proportion to the montmorillonite content, clay samples exhibited a fluidity and their LL values increased linearly. However, increasing degrees were different between them. At the extreme, M=100% sample took 895% from the Casagrande test, while 552% from the fall cone test.This discrepancy proved to result from the differences in physical procedures of both tests and from thixotropic properties of montmorillonite clay. Tensile strengths were also measured for the same samples with the use of simple force gauge. They expressed substantially the same tendency with LL tests and their tensile strengths were evaluated as 20-50 kPa in the state of LL.