Frustum confining vessel for testing model piles

A cone-shaped vessel, a frustum, has been developed for testing model piles. The magnitude of the confining stresses in the soil within the vessel can be controlled by applying pressure to a piston in the bottom of the device. A series of continous cone penetration tests was performed to determine approximate stress distributions with depth along the frustum axis. The penetration test results indicated that vertical stress within the soil mass increased with depth from zero at the top of the soil to a maximum value at the bottom, which is controlled by the stress applied to the bottom piston. Finite element analyses, which were carried out to establish stress patterns within the frustum confining vessel, confirmed the results obtained from the physical testing. This study demonstrates that the new confining vessel enables physical testing of small-scale model foundations under soil mass conditions that more closely reflect the in situ stress conditions encountered with full-scale foundations under in-service conditions. Key words: cone penetration resistance, confining stress, finite element analyses, frustum confining vessel, small-scale model testing, stress distribution.