FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

10 Designing the FounDation Volume II
Equation 10.2. ultimatE ComprEssion CapaCity of a singlE pilE
where:
Qult = ultimate load capacity in compression (lb)
PT = effective vertical stress at pile tip (lb/ft2) Nq = bearing capacity factor (see Table 10-4)
Table 10‑4. Bearing Capacity Factors (N q )
Parameter Pile Bearing Capacity Factors
(degrees) (a) 26 28 30 31 32 33 34 35 36 37 38 39 40
N q (driven pile displacement) 10 15 21 24 29 35 42 50 62 77 86 120 145
N q (drilled piers) (b ) 5 8 10 12 14 17 21 25 30 38 43 60 72
N q = bearing capacity factor
A T = area of pile tip (ft 2 )
KHC = earth pressure in compression (see Table 10-5)
P0 = effective vertical stress over the depth of embedment, D (lb/ft2 )
= friction angle between pile and soil (see Table 10-6)
s = surface area of pile per unit length (ft)
D = depth of embedment (ft)
= angle of internal friction
(a) Limit to 28° if jetting is used
(b) When a bailer or grab bucket is used below the groundwater table, calculate end bearing based on not exceeding 28 degrees.
For piers larger than 24 inches in diameter, settlement rather than bearing capacity usually controls the design. For estimating
settlement, take 50% of the settlement for an equivalent footing resting on the surface of comparable granular soils.
Table 10‑5. Earth Pressure Coefficients
Pile Type KHC KHT Driven single H‑pile 0.5 – 1.0 0.3 – 0.5
Driven single displacement pile 1.0 – 1.5 0.6 – 1.0
Driven single displacement tapered pile 1.5 – 2.0 1.0 – 1.3
Driven jetted pile 0.4 – 0.9 0.3 – 0.6
Drilled pile (less than 24‑inch diameter) 0.7 0.4
KHC = earth pressure compression coefficient
KHT = earth pressure tension coefficient
10-14 COASTAL CONSTRUCTION MANUAL