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7 Cards in this Set
- Front
- Back
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What is the nature of the most common type of foundation failure?
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Most foundation failures are due to excessive differential settlement - most commonly when a bldg. occupies a site with 2 or more areas of different types of soil with very diff. load bearing capacities. Gross failure of a foundation is extremely rare.
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List 3 different ways of sheeting an excavation.
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1. Soldier beams and lagging (can be removed after construction of substructure has been complete).
2. Sheet piling - left in place as part of substructure of bldg. or may be pulled when finished. 3. Slurry wall is more complicated and expensive. Workers weld together cages of steel bars designed to reinforce the concrete wall that will replace the slurry in the trench. |
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Under what circumstances would sheeting not be required?
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Excavations in fractured rock can often avoid sheeting altogether by injecting grout into the joints of the rock to stabilize it or by drilling into the rock and inserting rock anchors that fasten the blocks together.
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If shallow foundations are substantially less expensive than deep ones, why do we use deep foundations?
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Shallow foundations can be used where suitable soils is found at the level at the bottom of the substructure.
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Primary and secondary factors affecting choice of foundation type for a building are:
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Primary:
1. subsurface soil and groundwater conditions 2. Structural requirements, including foundation loads, building configurations, and depth Secondary: 1. Construction methods, including access and working space 2. Environmental factors, including noise, traffic, and disposal of earth and water. |
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What soil conditions favor the use of belled caissons?
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Belled caissons are practical only where the bell can be excavated in a cohesive soil (such as clay) that can retain its shape until concrete is poured and where the bearing stratum is impervious to the passage of water to prevent flooding of the hole.
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Which types of friction piles can carry the heaviest load per pile?
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Pipe piles are stiff and can carry heavy loads (50-150 tons).
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