Rule of Thumb = Friction Angle - 30 N{w)}me[YY
*uoc;6
For more details, please read I*hCIy#;
5F&xU$$a-
Bolton, M.D. (1986) The strength and dilatancy of sands tj7{[3~-[
qD0sD2 x
Vermeer & DeBorst (1984) Non-associated plasticity for soils, concrete and rock