Shallow Footing in Clay

[jrs]

Okay, perhaps one of you geotechs can help me. I think the answer should be 1.5ksf. Why is this not correct?

Q:

A 10-foot diameter circular footing bears at a depth of 5 feet in clay. The clay has a total unit weight of 110 pcf and an unconfined compressive strength (qu) of 0.8 tsf. Assume vertical concentric loading. What is the ultimate bearing capacity?

A. 4.5 ksf

B. 5.5 ksf

C. 10.4 ksf

 

[Daisy]

Using CERM equation 36.6 I came up with 6 ksf (using Terzaghi) and 5.5 ksf (using Meyerhoff). That's assuming phi = 0 for clay. Is B the correct answer?

 

[jrs]

Using CERM equation 36.6 I came up with 6 ksf (using Terzaghi) and 5.5 ksf (using Meyerhoff). That's assuming phi = 0 for clay. Is B the correct answer?

Yes, you are correct. (My error earlier was failing to use Nc from table 36.3 and only using the geometry adjustment. One more mistake I won't make on the 24th!)

 

[Daisy]

I've made plenty of the 'easy' mistakes preparing for this exam...I just can't wait for it to be over! Good luck to you!