×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Soil Subgrade Modulus on Rock

Soil Subgrade Modulus on Rock

Soil Subgrade Modulus on Rock

(OP)
My Geotech is on vacation...
So, I've got a mat foundation on a hard rock (gneiss) of very good quality.  The allowable bearing pressure on the rock is at 80 ksf.  Does anyone have a suggestion as to a reasonable modulus of subgrade reaction?  I'm figuring on somewhere between 12,000 pci and 8,000 pci.

RE: Soil Subgrade Modulus on Rock

A subgrade modulus for rock is not of much use. The modulus is defined as pressure/measured deflection. Rock, unlike soil, does not compress when pressure is applied (i.e. it will crack before its compressibility can be mearured). Thus, the rock will experience a brittle fracture failure instead of a slow compression as can be seen in most soils. If your allowable bearing pressure is exceeded, there most likely will be an immediate failure of the rock.

RE: Soil Subgrade Modulus on Rock

If you are just needing that value to put something in a matt design program I would use something in the order of 36*bearing pressure.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources