Highways Agency Reports

Abstract: Triaxial tests have been carried out on fills that can be described as unconventional. The shear strengths of gap-graded fills, with 15% and 30% of large particles in a fine matrix of sand, were compared with the matrix alone at a range of relatie densities. It was found that when present at 30%, the large particles provide additional strength whereas at 15%, they have an adverse effect. Possible mechanisms for these phenomena are discussed. Strength enhancement was still available when the "large" particles were of poor quality, friable limestone. These laboratory trials suggest that a more flexible specification for fill could lead to significant economies, but further field tests will be required for confirmation.