Question

Q4. An industrial building is to be supported on a series of 14 -in square prestressed concrete piles which will be driven 45 ft into the following soil profiles:

Depth (ft)	Soil classification	Friction angle phi^(') (deg)	Relative density D_(r)	N_(60)	Unit weight gamma (lb//ft^(3))
0-10.0	Silty sand (SM)	33	40%	12	100
10.0-16.5	Sandy silt (ML)	31	50%	16	110
16.5-35.0	Fine to medium sand (SW)	35	62%	30	125
35.0-65.0	Well-graded sand (SW)	37	68%	35	126

The groundwater table is at a depth of 15 ft and all of the strata may be assumed to be normally consolidated. These piles have been designed without the benefit of any onsite static load tests, dynamics tests, or indicator piles, but a wave equation analysis has been performed. The factor of safety for downward loading is 2.75, and the factor of safety for upward loading is 5.5 . Compute the allowable downward and upward load capacities of each pile.

Answer 1