Performance of a full depth asphalt pavement on an expansive clay subgrade

The paper deals with the performance of runway pavements constructed at a site that has an expansive clay subgrade. The study includes a conventional flexible pavement section with and without subsurface drainage, a full- depth asphalt pavement and a rigid pavement section. Precise level surveys were made after construction and at intervals up to 8 years after construction. The results show that the conventional flexible pavement distorted appreciably in both the longitudinal and transverse sections, whereas the full- depth asphalt pavement distorted only in the vicinity of utility sleeves and a culvert. The rigid pavement section heaved quite uniformly. The measured heaves are compared with those based on laboratory swelling studies on undisturbed subgrade samples. In these studies the estimated final equilibrium suction values have been accounted for by providing additional surcharge loadings over and above the overburden pressures in the laboratory swelling tests. The proposed method has proven to be both simple and reliable for various pavement types (a).