Question

Problem 5 You are to examine the retaining wall shown on Figure 2. Assume that the wall height (H) is equal to 12 feet, and the base width (B) is 7 feet. The wall will be approximately 200 feet long (into the page). The backfill material behind the wall is a poorly-graded sand with silt (ŚP-SM) that has an average total unit weight of 1 19 pounds per cubic foot (pcf) and an average water content of 12%. As indicated, a drainage system consisting of a granular drain layer and a perforated pipe will be installed behind the wall to help ensure that no water 'ponds' behind the wall during periods of wet weather. For design, it is assumed that the groundwater table is 3 feet beneath the ground surface (see Figure 2). (a) Assume that the lateral earth pressure coefficient for the backfill material is 0.40. Create a simple graph illustrating the effective horizontal stress distribution that exists behind the wall. Label important values of effective horizontal stress in pounds per square foot (psf). (b) Calculate the total horizontal force (in kips per foot of wall length) that acts on the wall for the situation described by Figure 2. Use a lateral earth pressure coefficient of Assume that the building contractor forgets to install the drain system behind the wall. As a result, during a rain storm, water ponds' behind the wall such that a groundwater table develops, Assume (c) ter table corresponds to the backfill elevation (elev. 100 feet), and calculate the total horizontal force (in kips per foot of wall length) that acts on the wall. The saturated unit weight of the backfill should be assumed to be 126 pounds per cubic foot (pc) for this problem. Again, use a lateral earth pressure coefficient of 0.40 Elev. 100 ft Backfill Material Wall Drain (Granular) Perforated Drain Pipe (holes down) Base 3 ft Figure 2 - Reinforced Concrete Retaining Wall.

Answer 1

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