Site Topography
Site Topography
(OP)
I am working on a project that has several drilled shaft foundations for a DOT Noise Barrier project. I was given the boring logs for the project, but the nearest boring natural grade elevation is about 10' above the natural grade elevation where my drilled shafts will be. The project is in Wisconsin so the topography is relatively rolling.
Would the correct procedure be to assume that soil layers follow approximately the existing grade contours or is there a better method (i.e. more conservative) to use for determining what soil layers the drilled shaft is situated in? Is 10' too much vertical difference to use for design? I wouldn't think so, but I am new to the drilled shaft game.
Would the correct procedure be to assume that soil layers follow approximately the existing grade contours or is there a better method (i.e. more conservative) to use for determining what soil layers the drilled shaft is situated in? Is 10' too much vertical difference to use for design? I wouldn't think so, but I am new to the drilled shaft game.





RE: Site Topography
RE: Site Topography
What is the noise barrier? Just a fence or is it an acoustic earth bund with a fence? I presume if you are using drilled they are supporting some sort of column or pole to which the barrier is attached to.
How long is the barrier? In an ideal world i would have boreholes drilled along the alignment of the barrier and would prepare a long section on which you could plot the different stratigraphy and soil strengths along the chainage. This would be very useful for a contractor.
RE: Site Topography
@EireChch
I believe the DOT provided alignment/bore locations is incorrect. We have an RFI in now for clarification. Thanks for the response.
RE: Site Topography
RE: Site Topography
to answer the question requires knowledge of the geologic history that created the land surface. as OG touched on it - glacial action is one process that could lower or raise the existing ground surface without affecting the older layers below. It is prevalent in Wisconsin. So a glacier could either leave a pile of material creating a hill or could create a valley by cutting through the layers.
However thrusting and faulting can result in folding and tilting of the geologic layers which is consistent with your theory that it follows approximately the contours. This would be more prevalent in mountainous areas.
You need a geologist to interpret things for you. For a drilled shaft, you might want a closer boring or get ready for a changed conditions claim.
RE: Site Topography