Empirical Factors for Miniature Cone and T-bar Penetrometers for Kaolin Clay

Undrained shear strength is a key parameter of clay and is popularly determined by penetrometers. Miniature penetrometers are preferred to estimate the undrained shear strength of clay for small-size model tests. In order to estimate undrained shear strength, an empirical factor should be established to correlate the tip resistance to the undrained shear strength. However, published data on miniature penetrometers are limited. This paper aims to evaluate empirical factors on miniature cone and T-bar penetrometers using a cylindrical chamber. Kaolin clay specimens were prepared in the chamber under five pre-consolidation pressures to control their undrained shear strength. Two miniature cones with diameters of 10 mm and 16 mm and a T-bar penetrometer with 10-mm diameter and 40-mm length were used to investigate penetration rate, boundary, and empirical factor. Unconsolidated-undrained triaxial tests and vane shear tests were carried out to measure undrained shear strength. Finally, empirical factors for the penetrometers were constructed to correlate tip resistance to undrained shear strength. The empirical factors established at 20 mm/s of a penetration rate for 10-mm-diameter cone, 16-mm-diameter cone and T-bar penetrometer are 18.33, 13.09 and 12.5, respectively.