CEE 380 HW12 Spring 2016 a - UNIVERSITY OF ILLINOIS...

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UNIVERSITY OF ILLINOIS, URBANA-CHAMPAIGN NAME: ______________ DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING DATE: ______Team:___ 1 CEE 380 - Spring 2016 HW #12 Shear strength of sands, shear strength of clays and coefficient of earth pressure Due 2 nd May, 2016 NOTE: PLEASE SHOW YOUR CALCULATIONS IN A CLEAR FORM REMEMBER TO INCLUDE UNITS IN YOUR CALCULATIONS PLEASE STAPLE YOUR WORK *NOTE: For this assignment, please draw all Mohr circles and/or Mohr-Coulomb failure envelopes on engineering/grid paper using a straight edge/ruler and a compass Part A Shear strength of sands 1. 3 consolidated undrained tests (with pore water pressure measurements) were run on a dense uniformly graded sand having rounded grains. The following data at failure was collected. Test σ 3f (kPa) σ 1f (kPa) u f (kPa) σ' 3f (kPa) σ' 1f (kPa) 1 150 425 50 2 250 650 100 3 350 890 150 a) Calculate the effective principal stresses at failure. b) Draw the Mohr’s circles for the 3 tests at failure using the effective stresses. Draw the Mohr-Coulomb failure envelope. c) What is the friction angle of the sand for the range of pressures used in the tests? What is the cohesion intercept? Compare with value of friction angle to typical values of dense sands. Are the results from the test reasonable? d) A 4 th test is run and the results are reported as follows: σ 3f = 200 kPa, σ 1f = 600 and u f = 100kPa. Plot the effective Mohr’s circle for this 4 th test on your plot from part (b). Would you trust the results from this 4 th test? Friction angle (degrees) Cohesion (kPa) Comparison to typical friction angles of uniform dense sand
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