Volume 32, Issue 6 (November 2009)
Re-evaluation of Laboratory Cone Penetration Method for High Liquid Limit Based on Free Swell Property of Soil
Percussion and laboratory cone penetration are two different methods employed for the determination of liquid limit of the soil. The empirical nature, advantages and limitations of these methods in determining liquid limit of the soil has been discussed in detail in the literature. One of the most important observations is that the soils with high liquid limit exhibits higher discrepancy between the two methods. There is a need to understand the reason for this discrepancy and to obtain identical values for all ranges of liquid limit. As an initial attempt, the present study reviews the possible reasons for the discrepancy in liquid limit values obtained by the two methods. Furthermore, a re-evaluation of the cone penetration method has been done and a modified penetration limit is proposed based on the free swell index of the soil. The cone penetration liquid limit was re-calculated by employing the modified penetration limit, and compared with the percussion liquid limit. It is noted that the modified penetration limit based on free swell property of the soil minimizes the difference in liquid limit values obtained by using both methods. It is further emphasized that the observations obtained from the present study cannot be compared with the field cone penetration results. The details of the experimental scheme adopted are described in detail in this technical paper.