1990 Volume 60 Pages 2-5
A hypothesis was performed on the A- line in the plasticity chart proposed by Casagrande for laboratory classification of fine- textured soils. By examining the results of tests on both the liquid and plastic limit published earlier on Bentonite, Illite and Kaolinite which are typical clay minerals, it was found that the relationship between the liquid limit (WL.) and plastic limit (Wp) could be expressed by the equation: WP 0.30WL +15.85 (WL≤120%) and Wp 69.8 ( constant) (WL>120%). On the basis of this linear relationship and the definition of the plasticity index (Ip), the following equation, which is closely similar to that of the A- line, was obtained as follows: IP 0.70 (Wl-22.6) (W≤120%).