CEMP-E
EI 02G001
01 July 1997
(1) For a vibratory hammer to be suitable for a particular application, the dynamic force
should suit the equation
Fdyn $ i ($o@Rso+$i@Rsi+$t@Rt)/R
where
Fdyn
=
dynamic force of vibrator, tons
=
beta factor for soil resistance (general)
$
=
beta factor for soil resistance (outside shaft)
$i
=
beta factor for soil resistance (inside shaft)
$o
=
beta factor for soil resistance (toe)
$t
Rsi
=
inside pile shaft soil resistance, tons
Rso
=
outside pile shaft soil resistance, tons
Rt
=
pile toe soil resistance, kN.
=
pile factor (0.8 for concrete piling and 1 for all
Q
other piling.)
=
soil resilience coefficient (should be between 0.6
i
and 0.8 for vibration frequencies between 5 and
10 Hz and 1 for all other frequencies.)
Suggested values for $ are given in table 2-2. The toe resistance and the outside and
inside (where applicable with open-end pipe and cylinder pile) shaft resistance should be
computed using methods similar to those employed for impact hammers. For extraction,
this formula is altered to read
Fdyn $ i ($o Rso+$i Rsi+$t Rt)/R-Fext
where
Fext
=
extraction force of crane, tons
(2) Once this is known, a possible vibratory hammer for the job should be selected
based on minimum permissible dynamic force in tons. The parameter of dynamic mass
(the dynamic mass includes any mass of the vibrator not dampened from vibration, the
clamp and any mass of the pile) should be noted, along with the frequency and eccentric
moment of the machine.
(3) Next the basic parameters of the vibratory hammer/pile system must be checked.
The first is the peak acceleration, whose value is computed using the equation
n = 2000 Fdyn / Wdyn
where
n
=
peak acceleration, g's
Mdyn =
dynamic mass of system, pounds
Minimum values for this acceleration are given in table 2-3.
Figure 2-2b. Method for Sizing Vibratory Hammers, English Units.
2-11
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