17
5.5.3 Resistances determined by stress wave
analysis
Determining end-of-driving criterias by stress wave
analysis is the preferred method for driven RR75 to
RR320 piles in piling classes PTL1 and PTL2.
Sec. 11 of these instructions and Appendix 3 present end-
of-driving criterias for different pile driving equipments,
piles and pile lengths (10, 20 and 30 m) based on the
one-dimensional stress wave theory using the GRLWEAP
program. Correlation factor
ξ
5
is 1.47 (1.40 x 1.05) according
to PO-2016 Part 1 Sections 4.5.2.4 and 4.5.2.6. The end-
of-driving tables present the targeted geotechnical
ultimate resistance at different piling class, design values
of geotechnical resistance R
d
corresponding to the
ultimate resistance, and end-of-driving criterias for each
pile driving equipment/pile combination. The design value
R
d
is obtained as follows:
R
d
= R
c
/(
ξ
5
x
t
)
= R
c
/(1.47 x 1.20) =
R
c
/1.764 (1)
The
R
d
values presented in the end-of-driving conditions
and Table 22 can be used directly in design for piling class
PTL1 and PTL2, and the geotechnical resistance of the pile
is ensured when the end-of-driving criterias are met.
In Table 22 the design values of geotechnical resistance for
PTL3 are calculated according to Formula (1). The design
values can be used as input values for design, and geo-
technical resistance must be ensured by dynamic load tests.
5.5.4 Resistances determined by dynamic load tests
Resistances determined by dynamic load tests are
suitable for friction and end-bearing piles at pile sizes
RR75 to RR1200 in all piling classes. Dynamic load tests
must always be used at building construction sites where
driven piles are used and the piling class is PTL3. In the
case of large diameter piles, dynamic load tests are
always recommended even with PTL2.
Correlation coefficients and related model coefficients
are presented in PO-2016. The dimensioning program
for RR and RD piles calculates correlation coefficients
automatically on the basis of input data.
Dimensioning based on dynamic load tests can in
principle be performed in two different ways.
1) The design value of geotechnical resistance
R
d
is
selected on the basis of piling class from Table 22, and
is used to calculate the minimum and average targets
for dynamic load tests.
2) The ultimate geotechnical resistance of the pile type
in question reliably achievable in the soil conditions of
the site is assessed considering the highest allowable
impact resistance of the piling class (Appendix 1),
and the design value of geotechnical compressive
resistance is calculated on the basis of this assessment
and dynamic load tests.
Table 15. Suitability of geotechnical dimensioning methods for different steel pile types.
Pile
static load test
dynamic load test
based on gr
ound test r
esults
end-of-driving criterias/
measur
ements based on pile driving formulas
end-of-driving instructions
based on str
ess wave
analysis
based on the behaviour of a corr
esponding foundation
RR small diameter piles/end-bearing piles PTL1–2
X
XX
X
XX
XXX
X
RR small diameter piles/end-bearing piles PTL3
X
XXX
X
XX
XX
X
RR large diameter piles/end-bearing piles
-
XXX
X
XX
XX
X
RR small diameter piles/friction piles
XX
XXX
XX
XX
XX
X
RR large diameter piles/friction piles
-
XXX
XX
XX
XX
X
CSG-RR piles/friction piles
XXX
-
XX
-
X
XX
Jacked RR-piles
XXX
X
XX
-
-
XX
RD piles
X
X
XXX*
X
X
X
Tension piles
xxx
x
xx
-
x
x
XXX = preferred method
XX = applicable
X
= possible, applicability to be assessed case by case
-
= technically infeasible or uneconomical
XXX* = RD piles feasible assuming that the bedrock surface has been reliably established or
that the bearing capacity of RD piles based on skin friction is determined by calculations