Factors Affecting the Pumping of Fines at the Subgrade Subbase Interface of Highway Pavements: A Laboratory Study

Abstract

This paper presents the results of a laboratory study using a Unit Cell Test and a modified 100 mm Triaxial Pumping Test. The effects of some of the factors affecting the pumping phenomenon are presented and discussed. A relationship between the amount of pumping and the permanent deformation of the system for the Unit Cell Test was obtained. The amount of pumping was found to be directly related to the cyclic deformation of the system. Based on statistical analysis of experimental results, an equation to calculate the amount of pumping in terms of the applied mean and cyclic stress was also developed. In the Triaxial Pumping Test, particular factors affecting the pumping phenomenon were studied which cannot easily be undertaken in the Unit Cell Pumping Test. Comparison of results with the Unit Cell Test showed that similar types of relationships existed between the amount of pumping and the permanent deformation of the system, and that the amount of pumping was generally less with the Triaxial Test.