University of California, Davis
Department of Civil and Environmental Engineering
ECI173 Foundation Design
MEMORANDUM
TO:
ECI173 Students
Date: January 12, 2011
FR:
Jason T. DeJong
SUBJECT:
Assignment No. 2 (Due by Friday, January 21 @ 5pm in Ghaussi, 2
nd
floor 173 HW dropoff box)
Question 1:
Using the Janbu method compute the immediate settlement for the following.
A square spread footing, 6 ft
in width and embedded 2 ft is subjected to 100k lb load.
The footing is embedded in a soft clay, which has
the following properties: undrained strength = 3000 psf, unit weight = 115 pcf, and an average OCR = 1.7.
The depth to bedrock from the original ground surface is 50 ft.
The PI is 55.
Solution
Compute terms for reading Janbu chart solutions:
H/B = 48/6 = 8
D/B = 2/6 = 0.33
I
0
= 0.95
I
1
= 0.7
From chart w/ PI = 55
K ~ 110
Eu = K (Su) =110 * 3000 psf = 33 ksf
q
b
= 100,000 lbs / 36 ft
2
= 2,778 psf
w
i
= I
0
I
1
q
b
B / Eu = (0.95) (0.7) (2778 psf) (6 ft) / 330,000 psf = 0.034 ft.
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View Full DocumentQuestion 2:
A 6story reinforced concrete frame structure is to be supported on a rectangular mat foundation that is 40 m
by 60 m in plan dimensions. The average bearing pressure imposed by the mat foundation will be 60 kPa.
The site is roughly flat with little surface vegetation or organic soil.
The mat will be 1.0mthick, and its top
surface will be roughly 0.5 m below the existing ground surface. Subsurface conditions consist of a 15m
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 Spring '11
 dejong
 Prime number, SPT N value, Mat Foundation, Davis Department of Civil and Environmental Engineering ECI173 Foundation

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