Harison (1988) stated a method for determination of plastic limit as shown in Figure4. Based on the figure, the upper line is used for determination of the liquid limit with arange of penetration value from about 14 – 15 mm. The lower line indicates the plasticlimit determination. Theoretically, according to assumption that the point of intersectionof the two line is at
d
2SL
= 14 mm, the lower line can be simply constructed by performingan additional penetration test until at say 5 mm. From the lower line, the water content at
d
PL
can be determined in which refer to the depth at 2 mm