The bearing capacity factors for estimation of short-term bearing capacity of shallow foundations resting on clay under undrained loading as per Terzaghi’s theory is
- A5.7, 1, 0Correct
- B5.14, 1, 0
- C5.14, 1, 1
- Dnone of these
Solution
Concept
Terzaghi's Bearing Capacity Factors for Clay
Formula
qult = 5.7c + q
Step-by-step solution
1. Identify cohesion (c) and effective surcharge pressure (q). 2. Multiply cohesion by 5.7 to find the cohesion component (5.7c). 3. Add the surcharge pressure (q) to get ultimate bearing capacity (qult = 5.7c + q).
Explanation
For saturated clay under short-term (undrained) loading, the angle of internal friction is zero (φ = 0). According to Terzaghi's bearing capacity theory for a strip footing under these conditions, the cohesion factor Nc is equal to 5.7, the surcharge factor Nq is equal to 1, and the unit weight factor Ngamma is equal to 0.
Shortcut
For Terzaghi's theory on pure clay (φ = 0): - Remember "5.7 - 1 - 0" - Terzaghi's Nc = 5.7 (unlike Skempton/Meyerhof which use 5.14) - Nq = 1 (surcharge stays as-is) - Nγ = 0 (clay's self-weight contribution is zero when φ = 0)
Common mistake
Many students confuse Terzaghi's bearing capacity factor Nc = 5.7 for clay with Skempton's or Meyerhof's value of 5.14, leading them to incorrectly choose Option B instead of Option A.
Correct answer: A) 5.7, 1, 0