Kpaudel, why not calculate or estimate thru estabilished correlations or standards the friction angle and then figure out the bearing capacity thru consolidated formulae?
In my place such soils display good strenght and stiffness although the Matrix may rule and cause weaker areas.
Sometimes the gravel is cemented and you have a proper rock, some other times there is lots of silty matrix and the gravel+boulders may behave more like a silt.