Subgrade Stress and Deformation Under Dynamic Load

An experimental investigation to determine the complete pattern of dynamic stress, strain, and surface deflections in a clay subgrade material subjected to a uniform surface contact pressure applied over a circular area is described. This is the first stage in a major research project, the aim of which is to obtain comprehensive information on the stress and deformation in a three-layer pavement structure under dynamic load. Details of calibration tests on transducers for measuring in-situ stress and strains are described. Results indicate stresses to be predicted adequately by elastic theory, but that strains, being dependent on the soil modulus, are less well predicted. At the low stress levels encountered, the soil stress-strain curve is markedly nonlinear.