Foundation on equivalent soil mass bedrock within a slope.
Foundation on equivalent soil mass bedrock within a slope.
(OP)
I have a project in which a bridge abutment foundation is proposed on bedrock of very poor quality and is being analyzed as equivalent soil mass. The foundation is also next to a slope. My question is do I need to evaluate the bearing resistance using AASHTO, 2010 Section 10.6.3.1.2c or will the fact that it is on bedrock, albeit very poor bedrock, negate this.





RE: Foundation on equivalent soil mass bedrock within a slope.
RE: Foundation on equivalent soil mass bedrock within a slope.
Like the previous poster already said, if extremely decomposed, a rock mass may behave like gravelly soil, otherwise like an isotropic poor quality rock mass, the best procedure would be to analyze it both ways, you may have a lower bound for the gravelly soil and an upper bound for the poor quality isotropic rock mass.
It stands to reason that the presence of the poor bedrock does not negate the evaluation of the bearing resistance since its behaviour approaches that of a soil mass.
RE: Foundation on equivalent soil mass bedrock within a slope.
RE: Foundation on equivalent soil mass bedrock within a slope.
the above reasoning may be incorrect though if the failure surface is constrained by some joints, like it can happen in jointed anisotropic rock masses. A very poor shale will be an isotropic medium with a behaviour similar to soil, probably it is reasonable to assume that the failure surface under the foundations will follow a pattern similar to that of soils.