Analysis of cone penetration and indentation tests in clayey soils

Penetration tests with 20 mm diameter steel cones have been made in large cylindrical samples of a reconstituted artificial clayey silt. A relationship is given between the point resistance q(c), the apex angle of the cone 2 theta, and the undrained shear strength S-u. For all cone angles, the results agree with Baligh's penetration theory. The experiments show that the point resistance first decreases with increasing cone angles and reaches a minimum value for a cone angle of about 60 degrees, then it increases again with increasing cone angles, up to a maximum value attained for a flat cone. Penetration tests have also been carried out from the bottom of drilled vertical holes in order to examine the mobilization of point resistance with depth. The results indicate that the maximum point resistance is reached after very small penetrations and is much higher than that predicted by the theory of expansion of cavities in elastic-plastic materials. In addition, indentation tests were carried out using the 60 degrees apex angle cone on two different artificial clayey silts. These tests allow the determination of undrained shear strengths of clays by means of indentation theory.