the sum of the static soil (displacement dependent), *Q*u and the

dynamic (velocity dependent) *D *components are of the capacity.

(b) Static soil capacity *Q*u can be calculated from *R *by

(6-2)

where *V*top is the velocity of the wave measured at the pile top at

time *t*1. Approximate damping constants *J*c have already been

determined for soils as given in Table 6-2 by comparing Case

method calculations of static capacity with results of load tests.

are available.

(c) Proper calculation of *Q*u requires that the displacement

the quake (soil compression) required for full mobilization of

soil r esistance. Selection of time *t*1 corresponding to the first

maximum velocity is usually sufficient.

(d) A correction for ealy skin friction unloading causing a

negative velocity may be required for long piles with high skin

friction. The upper shaft friction may unload if the pile top is

moving upward before the full resistance is mobilized. A proper

correction can be made by adding the skin friction resistance that

was unloaded to the mobilized soil resistance.

(e) Proper calculation to static resistance requires that freeze

or relaxation effects are not present. Piles may be restruck after

a waiting period such as 1 day or more to allow dissipation of

pore water pressures.

(f) The driving force must be sufficient to cause the soil to

fail; otherwise, ultimate capacity is only partially mobilized and

the full soil resistance will not be measured.

(3) CAPWAPC method. This is an analytical method that

combines field measured data with wave equation analysis to

calculate the static ultimate bearing capacity and distribution of

pile load-displacement behavior calculated by the CAPWAPC

method may be used to evaluate the damping constant *J*c ,

quakes and soil resistances required in the Case method, and to

confirm the determination of *Q*u calculated using the Case

method. The CAPWAPC method is often used as a supplement

to load tests and may replace some load tests.

(a) The CAPWAPC method is begun using a complete set

of assumed input parameters to perform a wave equation

analysis. The hammer model, which is used to calculate the pile

velocity at the top, is replaced by a velocity that is imposed at the

top pile element. The imposed velocity is made equal to the

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