Exam 2013 Geotechnical Engineering 2, questions and answers

Question 1 - Multiple Choice Questions (Mark: 18 X 3 = 54) Identify the choice that best completes the statement or answers the following questions. QUESTION 2 A retaining wall 6 m high supports a soil of saturated unit weight of 18 kN/m3 and φ =30°. The backfill is subjected to a surcharge of 20 kPa. 1. Calculate the total horizontal component of the lateral active force on the wall if the wall is rough (=18°). Groundwater is at the ground surface above the backfill soil. ka (Coulomb) =0.42 (17 Marks) 2. Plot the retaining wall and show the orientation and location of all lateral forces on the back of the wall. QUESTION 3 (6 Marks) A square footing subjected to a vertical load of 500 kN and a moment about the Y axis of 125 kN.m, is located at a depth of 1 m below the ground surface in a deep deposit of compacted sand (φ =33°, sat = 19 kN/m3 and  = 17.0 kN/m3). Water level is at the bottom of the footing. Calculate: 1) Ultimate bearing capacity (Nq = 27 and N = 30.5) IF THE WATER TABLE RISES TO THE SURFACE AFTER A HEAVY RAINFALL. (18 Marks) 2) Factor of safety FOR WATER TABLE AT THE SURFACE. (5 Marks) Question 2: Coulomb’s Method 20 kPa Pac+Ps Pw h/3 Distributing prohibited Location h/3 = 6/3 =2m from the base of the wall Question 3: 1) ( )