Behaviour of weathered rock

[dimos3]

A one storey building and a highway bridge are going to be constructed on a site, in which the site investigation indicated about 10m of highly weathered travertine overlying fresh travertine.

No rock cores were obtained within the weathered rock and the samples taken look like sand (with some traces of fresh rock). Cliffs in the area consisting of this material stand literally vertical.

So, how do you think this material behaves under loading? As a loose sand as the SPT results show, as a sand with some cohesion or as a rock with really low engineering properties??

Thanks!

 

[ishvaaag]

I would say that since your structures are to stay for a normal lifespan, as the loose sand. Further meteorization may bring this behaviour to your soil. This doesn't mean however that you need entirely forfeit any intelligence standing from the investigation of the placement.

 

[hokie66]

Why ask us? You should be asking the geotech who did the site investigation.

Having said that, it is not surprising that the product of boring in highly weathered rock looks like sand. But if it is highly weathered rock in situ, it should behave as such. As to travertine specifically, I don't have any experience with founding on that.