MEASURING THE PENETRATION RESISTANCE OF SOIL USING DYNAMIC CONE PENETROMETER

Abstract

Recognition of the importance of soil compaction is increasing, but instrument cost, repeatability of measurements, and data interpretation restricts its measurement. Developed by Scala (1959), the dynamic cone penetrometer (DCP) device has been substantially utilized in recent decades for quality control of compaction of soils. The dynamic cone penetrometer described in this study follows the design of the American Society of Testing and Materials standards.

The penetrometer cone is pushed into the soil by giving successive hammer blows. Penetration resistance is calculated as the work done by the soil needed to stop the motion of the cone divided by the distance that the cone penetrates. The work done by the soil is defined as the kinetic energy of the hammer while it impacts the strike plate. The height of fall of the hammer has been varied for each test to vary the kinetic energy on impact. The effect of the variation of the apex angle of the cone on the Dynamic Cone Penetration Index(DCPI) and the soil penetration resistance has also been studied in this work. Numerous cone angles other than the standard 60 degree cone were designed and used for testing the effects and the results have been compared.

The results show that the average soil penetration resistance obtained for a depth of 15 cm is almost similar for the various tests on the same soil sample, each with a different height of fall of the hammer. The penetration resistance for four soil samples was then calculated using a fixed height of fall of 400 mm for each. The results also show that the DCPI value decreases as the apex angle of the cone is increased further from the standard 60°, although this similar sort of trend is not observed for the lower values of the cone angle.