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Technical Committee 212 /
Comité technique 212
settlement relations for both pile types are nearly linear. Due to
conventional procedure of tests, the results did not provide any
information regarding the distribution of loads transmitted by
the shaft and by the base of piles into the subsoil.
Figure. 4. Soil conditions and SPLT results of Vibro and Franki piles
tested for bridge over the Vistula river project
2.2.
Tests on Vibro pile under road viaduct in Gdansk
More advanced static load test has been carried out for
508/560 mm Vibro pile installed under the foundation of road
viaduct in Gdansk. In the test the distribution of load between
shaft and base of the pile was measured. For this purpose
a system of 7 extensometers have been installed inside the pile
shaft in order to measure shaft strains. The principle of
extensometric system work is commonly known, (Bustamante
and Diox 1991, Hayes and Simmonds 2002, etc.). The
assessment of axial load at various pile levels is based on the
shortening measurement of individual pile sectors. Subsequent-
ly, the load transmitted into the particular soil layers over the
pile shaft and under its base are determined.
Basic
Q
-
s
diagram representing settlement of the pile is
presented in Fig. 5. In turn, the distribution of axial load in the
pile for subsequent load levels obtained from the extensometric
measurements is shown in Fig. 6. In Fig. 7 the results of further
interpretation of the measurements in terms of unit friction
resistances
t
si
over the pile shaft in particular soil layers and unit
resistance under the pile base
q
b
are presented. The unit
resistances have been expressed as a function of displacement
of corresponding pile sectors.
Figure. 5. Basic result from static load test of instrumented Vibro pile
Figure. 6. Distribution of axial load in the instrumented Vibro pile
Figure. 7. Unit friction resistances
t
si
over the shaft in particular soil
layers and unit resistance
q
b
under the base
of instrumented
Vibro pile
There are main observations and conclusions drawn from the
analysis of the results of extensometric measurements:
large part of external load applied to the pile head has been
overtaken by the friction resistance of upper sandy soil
layers which exist in the subsoil to the depth of 14 m, still
over the mud layers;
small portion of total load reached the level of pile base.
The value of
Q
b
force transmitted by the pile base in the
