Repetitive Load Deformation of Cohesionless Soil

Presented is a simplified procedure for obtaining material characterization of free draining cohesionless soils for use in calculating permanent deformations of transportation support systems. Experimental data is presented in support of the described simplified procedure, which shows that plastic strains are largely governed by the deviator stress level and, thus, the factor of safety against shear failure. Plotting logarithm of plastic strain versus logarithm of number of load repetitions resulted in a slope essentially independent of confining pressure or deviator stress level for stress levels less than 60%. Plotting logarithm of plastic strain at a given number of load cycles versus deviator stress level resulted in a slope which was essentially constant. These two findings allowed the development of the presented procedure resulting in a method of obtaining material characterization which gives a significant savings in laboratory testing time over present methods. Such material characterization is an essential requirement for predicting the rate of accumulation of permanent deformation (rutting) using the well-known layered elastic or non-elastic technique.