INVESTIGATION OF SOILS SUBJECTED TO DYNAMIC LOADING.

The findings of a field and laboratory investigation into the causes of distress in flexible pavements are presented. Three pavements where distressed zones occurred adjacent to sound sections were tested. An attempt has been made to explain the causes of localized failures on the basis of elasticity theory. In the case of two of these roads it was found possible to predict the causes of the distress noted. The concept of threshold stress, put forward in the earlier report, is examined from the standpoint of linear viscoelastic theory. The difficulties of applying viscoelastic theory to multilayer systems where one or more layers possess a threshold stress is discussed. It is shown that viscoelasticity is a cumbersome theory to apply in practice. An alternative rate theory is developed for estimating the permanent displacements in a stress pavement. The theory is based on the formulation of a stress-strain law for clays in repeated loading. The predictions of the rate theory are shown to be in satisfactory agreement with some data obtained in the A.A.S.H.O. Road Test. The construction and instrumentation of an experimental road is described. Some experiences gained in the investigation of this full-scale experiment is presented. (Author)