Pile Capacity From Driving Data Equations and Calculator

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Pile Capacity From Driving Data Equations and Calculator

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Pile Capacity From Driving Data Equations and Calculator

The safe load (safe bearing value) can be calculated empirically from installation data using the Engineer News Record (ENR or Engineering News) equations.

Preview: Pile Capacity From Driving Data Calculator

For a pile driven in by a drop hammer of weight W, falling a distance H_hammer, driving a weight of W_driven (including the pile weight), and penetrating an average distance S per blow during the last five blows, the maximum allowable vertical load per pile, Q_a, referred to as design capacity and pile resistance, is calculated as 1/6 of the ultimate strength and, incorporating the conversion from feet to inches, is

Eq. 1,
Drop Hammer
Q_{a, lbf} = Q_ult / ( F · S ) = ( 2 · W_hammer,lbf · H_fall,ft ) / ( S_in + 1 )

Eq. 2
single-acting steam hammer;
driven weight < striking weight
Q_{a, lbf} = ( 2 · W_hammer,lbf · H_fall,ft ) / ( S_in + 1 )

Eq. 3
single-acting steam hammer;
driven weight > striking weight
Q_{a, lbf} = ( 2 · W_hammer,lbf · H_fall,ft ) / ( S_in + 0.1 ( W_driven / W_hammer ) )

For double-acting (i.e., powered) hammers, the energy, E_ft-lbf, transferred to the pile on each stroke replaces the WH potential energy term. Typical values of energy per blow for timber piles are 7500–14,000 ft-lbf (10–19 kJ) for single-acting hammers and 14,000 ft-lbf (19 kJ) for double-acting hammers. For concrete and steel piles, the typical energy per blow is 15,000 – 20,000 ft-lbf (20–27 kJ).

Eq. 4
double-acting steam hammer;
driven weight < striking weight
Q_{a, lbf} = 2 · E_ft-lbf / ( S_in + 0.1 )

Eq. 5
double-acting steam hammer;
driven weight > striking weight
Q_{a, lbf} = 2 · E_ft-lbf / ( S_in + 0.1 · ( W_driven / W_hammer ) )

Correlations with standard penetration tests (i.e., those that derive the N-value) have also been established and can be used with adequate testing.

Where

Q = vertical load capacity or (design capacity and pile resistance), lbf
W = Force or weight of hammer or pile driven, lbf
S = average penetration per blow, ft
E = energy per blow, ft-lbf
H = height hammer dropped, ft

Also see: (free membership required for document)
Field Estimates of Pile Capacities

Source

Civil Engineering Engineering Reference Reference Manual for the PE Exam for the PE Exam
Fourteenth Edition
Michael R. Lindeburg, PE