A shear key construction requires crushed rock materials, with maximum sizes between 6 and 8 in. What typical gradation should be selected to get the maximum density without compaction effort. The crushed rock will be dumped by the excavator bucket (no compaction), after a 3m wide shear key trench (up to 6m deep)is excavated. The surrounding soil consists of clay. This shear key is used to stabilized a slope.

When I was working on asphaltic concrete mix design, there was a chart that can be used to plot the gradation to ensure minimum air voids. Is this the right way to do ? We do not want to have one size stones, since it will have lots of voids and clay will go into the trench. But we do not want too much fines either, because it will not have a good drainage.

Thanks for the help.