Loading Rate Effect on Piles in Clay from Laboratory Model Tests

Abstract

The strength of cohesive soils is affected by the rate at which the external load is applied. Bearing capacity of foundations is also affected by the rate of loading since it is a function of the shear strength of soils. In this study, the influence of loading rate on the axial capacity of piles in clay is experimentally investigated. Two series of model tests were carried out using a steel model pile having a diameter of 30 mm under different loading rates. The first group of tests was performed under axial compression loads, while the model pile was subjected to axial uplift loads in the second set of tests. In addition, consolidated undrained triaxial tests were performed under the same loading rates used in the axial capacity tests. Compressive and uplift axial capacities of the model pile were found to increase as the loading rate increases. The relationship between time to failure, and both the undrained shear strength of the clay and the axial capacity of the model pile can be represented by a straight line on a log-log plot.