STABILITY OF GRAVEL SUB-BASES

As part of an investigation into the stability of unbound granular subbases a series of trafficking trials has been carried out with loaded lorries on several types of crushed rock and gravel subbases. 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 subbases can perform as well as crushed rock type 1 subbases. The shear box test, however, was only able to distinguish between the least and most stable; for most subbase materials a trafficking trial would be needed to verify their stability. (a)