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Assign_2_2011

# Assign_2_2011 - The mat will be 1.0-m-thick and its top...

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University of California, Davis Department of Civil and Environmental Engineering ECI-173 Foundation Design MEMORANDUM TO: ECI-173 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 drop-off 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. Question 2: A 6-story 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.
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Unformatted text preview: The mat will be 1.0-m-thick, and its top surface will be roughly 0.5 m below the existing ground surface. Subsurface conditions consist of a 15-m deep alluvial deposit of sands (USCS classifications were SP and SP-SM) overlying competent bedrock. The groundwater table varies between depths of 8 and 10 m. Three rotary wash borings with Standard Penetration Tests (SPTs) were performed within the building footprint (fewer borings than would be required, but this keeps the problem simpler), and the N values (or blow counts) are summarized below. An old safety hammer was used that was shown to have an average energy ratio of 50%. Depth (m) Measured SPT N value Boring #1 Boring #2 Boring #3 0.5 8 11 6 1.25 17 22 33 2.0 20 16 23 2.75 24 22 21 3.5 34 18 36 4.25 31 16 22 5.0 22 24 28 6.5 41 29 43 8.0 49 44 47 9.5 38 33 31 11. 51 50 49 12.5 59 38 35 14 44 43 51 Estimate the settlement of the mat foundation after 3 years of service....
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