Chapters 11 and 12

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Reading Assignment
Chapters 11 and 12
Textbook:  Soil in Construction: 6th Edition – W. L. Schroeder, S.E. …
 
 
Chapter 11 ◆ Shallow Foundations and Pavements
 

  1. Footings for a structure are to be built beneath a basement slab on a clay soil at a depth of 20 ft below present ground level. Representative consolidation tests on the soil produce results typified by Figure 5.9. The groundwater table is 15 ft below the ground surface. The soil-void ratio is about 0.87. If the average bearing pressure on the footings is 2,600 psf, estimate the settlement of 10-ft and 5-ft-square footings.
  2. What is the factor of safety for the footings in Problem 1 against bearing failure if the clay soil has an unconfined compressive strength of 3,600 psf?
  3. What is the maximum column load in kips that could be placed on a 4-ft square temporary footing on a sand for which the standard penetration resistance is about N60 = 15 and the water table is at the surface? A factor of safety of 2 is to be maintained against bearing failure.
  4. Solve Problem 3 if settlement of the footing must be limited to 1/2 in.

 
 
Chapter 12 ◆ Deep Foundations

  1. Six hundred timber piles are to be driven to a depth of 40 ft in sandy silt below the water table. The soil has a wet unit weight of 105 pcf. Compute a representative ultimate pile capacity if minimum tip diameter is 8 in and minimum butt diameter is 20 in. Suggest a type and size of pile-driving hammer, using the Engineering News formula. The pile design load is 50 kips. Justify your choice and describe what problems you might encounter.
  2. According to the provisions of a contract you are preparing a bid for, 12 in square prestressed concrete friction piles are to be driven to an ultimate capacity of 200 kips in a soft to medium clay deposit, assuming the soil unit weight is 100 pcf and the water table is at the surface. Capacity is to be verified by the Gates formula and lengths are not specified. Select a tenta-tive hammer type and size, justifying your choice. How long should the piles you furnish be? Describe problems you might encounter.
  3. Figure 10.27 shows the soil profile at a building site. Shaft foundations are to be used and design requirements dictate two alternatives. The first employs belled shafts with 6-ft diam-eter tips at 26 ft in depth. The second requires 2-ft-diameter straight shafts to 42 ft in depth. Which alternative would you prefer to build? Justify your answer, giving the advantages and disadvantages of each alternative.
  4. In Example 12.3, assuming that the contractor persisted in using the Gates formula to size the hammer, what hammer energy would be required to drive the pile at the given blow count specification? 5. In Example 12.3, verify that the stresses reported from the wav