The effect of gravel content and shape on shear strength of sand-gravel mixtures was investigated through a series of direct shear tests under different stress states (σ = 50

100

150 and 200 kPa) in laboratory. Mixtures were made up of sand with rounded and angular gravels

respectively. The gavel contents of 20%

40%

60% and 80% were used in sample preparation. The results indicate that the dilatancy and shear strength of sand-gravel mixture increase with increasing gravel content and irregular degree of gravel shape. The gravel content has a more visible effect on the shear strength rather than that of the gavel shape. The minimum void ratio of the mixture is a characteristic parameter to investigate the relationship between gravel content & shape and the shear strength of sand-gravel mixture.