Abstract
As part of an investigation into the stability of unbound granular sub-bases a series of trafficking trials has been carried out with loaded lorries on several types of crushed rock and gravel sub-bases. The results of these trafficking trials are correlated with shear strengths measured in a 300 mm shear-box machine modified to test wet aggregates with plastic fines. Precision estimates of this test method are given. It was found that many gravel sub-bases can perform as well as crushed rock type 1 sub-bases. The shear-box test, however, was only able to distinguish between the least and most stable; for most sub-base materials a trafficking trial would be needed to verify their stability. (Author/publisher)