Homework 7 - 2009

Homework 7 - 2009 - excavation to keep the excavation...

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The University of Missouri-Columbia Department of Civil Engineering Assigned: Friday, September 25, 2009 Due: Friday, October 2, 2009 CE 3400 – Fall 2009 Homework No. 7 – Capillarity and Uplift 1. A 40-foot thick layer of saturated clay is underlain by a layer of sand as shown below. There are artesian water pressures in the sand. Calculate the maximum depth of cut, H, that can be made in the deposit without the bottom of the excavation becoming unstable. (Assume the total head in the sand is constant). 40 ft. 15 ft. H = ? 30 ft. Clay Sand γ sat = 120 pcf γ sat = 118 pcf 2. An 8-meter thick layer of saturated clay is underlain by a layer of sand as shown below. An excavation is to be made in the clay to a depth of 6 meters. There are artesian water pressures in the sand. What depth of water, h, must be left in the
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Unformatted text preview: excavation to keep the excavation stable? (Assume the total head in the sand is constant). 8 m. 3 m. h = ? 7 m. Clay Sand 6 m. sat = 130 pcf sat = 115 pcf 3. A soil profile is shown below. The water table is 30 feet below the ground surface and there is capillary rise in the overlying clay to a height of 20 feet above the groundwater table. Compute and plot the variation in total stress, pore water pressure and effective stress from the ground surface to a depth of 45 feet. Plot depth on the vertical axis, with zero at the top and increasing downward. Plot all three stresses (total pore water and effective) on the same diagram. 10 ft. 20 ft. Dry sand Clay (Zone of capillary rise) 15 ft. n = 0.4, G s = 2.65 e = 0.48, G s = 2.72, S r = 100% e = 0.90, G s = 2.70, S r = 100% Clay...
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Homework 7 - 2009 - excavation to keep the excavation...

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