×
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

Bearing Capacity - Rock

Bearing Capacity - Rock

Bearing Capacity - Rock

(OP)
I am designing a foundation on rock with a UCS = 50 MPa.

The RQD is about 55% and RMR is about 30. When I refer to Bienawski Table for Rock Classification it gives:
C = 150 kPa
Phi = 20 deg

for the rock mass.  These give an allowable bearing capacity of 200 kPa.

When I refer to Goodman Rock Mechanics book, it suggests:

C = 0.25 (UCS) = 12.5 MPa
phi = 30 deg

for the rock mass.  These give an allowable bearing capacity of 5000 kPa.

I cannot understand why the results are so much different.

It would be appreciated if you let me know where is the problem.  Thank you.

RE: Bearing Capacity - Rock

(OP)
Corrections:

I am designing a foundation on rock with a UCS = 50 MPa.

The RQD is about 55% and RMR is about 30. When I refer to Bienawski Table for Rock Classification it gives:
C = 150 kPa
Phi = 20 deg

for the rock mass.  These give an allowable bearing capacity of 1100 kPa.

When I refer to Goodman Rock Mechanics book, it suggests:

C = 0.25 (UCS) = 12.5 MPa
phi = 30 deg

for the rock mass.  These give an allowable bearing capacity of 2500 kPa.

I cannot understand why the results are so much different.

It would be appreciated if you let me know where is the problem.  Thank you.  

RE: Bearing Capacity - Rock

Check out Tomlinson's Foundation Design and Construction book - good presentation.  Rock is sometimes a very strange bedfellow for something one thinks is cake.

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