(5)

Recompute the ultimate unit pile resistance using the formula

Su' = 3 Rd/As

where

Su' =

ultimate pile resistance per unit area for 8 blows

per centimeter (20 BPI) case, kPa. This value

should not fall below 6200 kPa with concrete piles

or 62,000 kPa with steel piles for subsequent

computational purposes

(6)

Compute the minimum rated striking energy for the pile hammer for the particular pile at 8 blows

per centimeter (20 blows per inch.) The formula used depends upon whether the pile is steel or

concrete.

Er 20BPI

= Su' As/(100.78 e(-Su'/22989)) . . . . . . . . . . . . . . . . . . . . . . . Concrete Piles

Er 20BPI

= As Su'1.68/165486 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steel Piles

where Er 20BPI

= minimum hammer rated striking energy at 8 blows per centimeter (20 blows per inch)

of resistance, kJ.

(7)

The minimum rated striking energy for the hammer is the greater of Er 10BPI and Er 20BPI.

(8)

Compute the minimum ram weight. Having computed the minimum rated striking energy for the

hammer, one or more hammers can be selected as possible candidates for driving the pile. The

equivalent stroke should be then computed by the equation

Seq = 102 Er/ms

where

Seq

=

equivalent stroke, m. This value should not exceed 2.44m for subsequent

computational purposes

Er

=

rated striking energy of the hammer, kJ

ms

=

ram mass of the hammer, kg

(9)

The minimum ram mass for each hammer can be computed for concrete and steel piles by the

equation

msmin

= 17659 As/(Seq) . . . . . . . . . . . . . . . . . . . . . . . . . . . Concrete Piles

msmin

= 161068 As/(Seq) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steel Piles

where

msmin

=

minimum ram weight, kg

A hammer should be rejected if its ram weight is less than the minimum ram weight, and other hammers

considered until one has been selected with a sufficiently large ram.

Figure 2-1a. (Concluded)

2-6