In this study, the Influence of rate of loading on uplift capacity of pries In clay is experimentally Investigated. Uplift capacity tests were conducted under different loading rates using a model steel pile having an outside diameter of 30 mm~ In addition, consolidated undrained triaxlal tests were performed under the same loading rates used tn the uplift capacity tests. Experimental results showed an Increase in undrained shear strength of the tested soil with the Increased rate of loading. Furthermore, the uplift capacity of the model pile was found to Increase as the loading rate increased. The relationships between loading rate, and both the undrained shear strength and the uplift capacity can be represented by a straight line on a log-log plot. Theoretical bearing capacity was calculated based on the undrained shear strength measured in the trlaxiai tests and compared with the measured uplift capacity under the same loading rate.
The strength of cohesive soils is affected by the rate at which the external load is applied. Laboratory studies have shown that the undrained shear strength of clays increases as the rate of loading increases (Casagrande and Wilson, 1951; Richardson and Whitman, 1963; Kimura and Saitoh, 1983; Nakase and Kamei, 1986, Sbeahan et al., 1996). It was found from the conventional triaxial tests of different types of clays that the undrained shear strength increases by about 10% for every 10-fold increase of strain rate (Kulhawy and Mayne, 1990). Because bearing capacity of foundations is a function of the shear strength of the soft, the capacity will also depend on the rate at which the external load is applied. A review of the literature indicates that research into the effect of rate of loading on the bearing capacity of both shallow and deep foundations is scanty.
