CE Section Quiz 03

1. What height retaining wall must be built to resist a total earth pressure force of 5,000 lbs. if the total unit weight of the soil is 135 pcf and has a friction value of 24 degrees?

2. Determine the unit weight (ɣ, in lb/ft³) and the dry unit weight ((ɣ_d, in lb/ft³) of a soil with the following conditions: Standard Proctor test weight (W) = 4.80 lbs. and Moisture content (w) = 10.77%. Volume of a Standard Proctor mold (V) = 1/30 ft³.

3. What is the degree of saturation (S) of the following soil? Maximum dry density = 130 pcf, Optimum Moisture Content = 10.77%, Specific gravity of the solids (G_s) = 6.35. Unit weight of water (ɣ_w) is 62.4 pcf.

4. In the drawing shown, what is the total pressure at the point shown? The pore water pressure = 3.121 psi and Z_w = Z₂ and Z₁ = 30 ft.

5. A 20 ft thick layer of consolidated clay has a 5 ft thick layer of sand on top and a 15 ft thick layer of sand beneath. How much time is required to reach 95% consolidation in a soil with a consolidation coefficient (c_v) of 0.5 ft²/day?