Shallow and Deep Foundations Flashcards
7 cards from real Civil Engineering PE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Shallow and Deep Foundations flashcards as text
A 2.5-ft wide strip footing is founded 3 ft below grade in clay with Su = 800 psf. Using Hansen's bearing capacity factors (Nc = 5.14, sc = 1.0 for strip), the gross ultimate bearing capacity is approximately:
Answer: 4,112 psf + overburden
q_ult = Su × Nc = 800 × 5.14 = 4,112 psf (net), plus the overburden pressure γDf = 120 × 3 = 360 psf for gross capacity.
The wave equation analysis (WEAP) for driven piles is used primarily to:
Answer: Predict driving resistance and evaluate hammer-pile-soil system performance during installation
WEAP models stress wave propagation to predict blow counts at refusal, check driving stresses, and confirm pile capacity during installation.
For a rectangular footing with dimensions B × L, the Meyerhof shape factor for the cohesion term (sc) is:
Answer: 1 + 0.2(B/L)Kp
Meyerhof's shape factor for cohesion is sc = 1 + 0.2(B/L)Kp, where Kp = tan²(45 + φ/2).
An H-pile driven to rock refusal develops its load primarily through:
Answer: End bearing at the pile tip with minimal skin friction contribution
H-piles driven to rock refusal rely almost entirely on end bearing since the relatively small tip area concentrates stress at the rock surface.
The Davisson offset limit method for determining pile capacity from a static load test uses an offset of:
Answer: 0.15 in + pile diameter/120
Davisson's criterion defines failure at a settlement equal to the elastic compression of the pile plus an offset of 0.15 in + D/120 (where D is diameter in inches).
Immediate settlement of a footing on saturated clay under undrained loading is calculated using:
Answer: Elastic theory with undrained modulus Eu and Poisson's ratio νu = 0.5
Immediate (elastic) settlement under undrained conditions uses elasticity theory with the undrained Young's modulus (Eu) and νu = 0.5 for incompressible behavior.
When eccentricity of loading on a footing exceeds B/6, the pressure distribution beneath the footing:
Answer: Develops tensile stress on one side, meaning only part of the footing is in contact with soil
When e > B/6, the resultant falls outside the kern, causing uplift (tension) on the far edge — since soil cannot take tension, the effective footing area reduces.