hw6-sp10 - existing 285 kPa) that this soil at this depth...

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CE 467L Geotechnical Engineering Spring 2010 Homework 6 Due: Thursday, March 25, 2010 1. Problem 4.1 in Craig. 2. Below are results of four direct shear tests on a dry sand. The specimen was cylindrical in shape, with a diameter of 50 mm and a height of 25 mm. Draw a graph for shear stress at failure versus normal stress. Determine the friction angle, φ′ for this soil (assume c = 0). Test No. Normal force (N) Shear force at failure (N) 1 271 159 2 406 226 3 474 264 4 542 308 3. For a given horizontal sand deposit, at a given depth, the in situ vertical effective stress, σ v , is 285 kPa, and the horizontal effective stress, σ h , is 145 kPa. There are no shear stresses acting on the horizontal and vertical planes. For this soil, for the given stress level, the Mohr-Coulomb strength parameters were determined to be φ′ = 33 ° and c = 0 (secant method). What is the maximum additional vertical effective stress (over and above the
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Unformatted text preview: existing 285 kPa) that this soil at this depth can withstand before failure? 4. An unconfined compression test was conducted on a soft clay. The specimen was trimmed from an undisturbed tube sample and was 35 mm in diameter and 80 mm tall. The specimen reached failure after 11 mm of axial deformation, at which time the axial load was 14.3 N. Calculate the unconfined compressive strength and the undrained shear strength of the specimen. Axial (total) stress at failure should be calculated as per Bardet, page 417: σ = F A c where F = the axial force, and A c = current specimen cross-sectional area = A i /(1 - ε ), where A i = initial specimen cross-sectional area and ε = axial strain at failure. 5. Define overconsolidation ratio (OCR). (Section 4.4) 6. List some examples of geologic factors that contribute to a clay being overconsolidated. (Section 4.4)...
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This note was uploaded on 09/13/2010 for the course CE 467L taught by Professor Rechenmacher during the Spring '10 term at USC.

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