2789
Technical Committee 212 /
Comité technique 212
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
3
Besides the wide red clay layer, observed in the SPT borings,
the soil presented a great variability in the Nspt resistance
values what justified the development of the modeling for such
construction.
3.1
Horizontal Slicing of Nspt Values
To detect with more preciseness the places with soft soil many
horizontal slicings were done where the values in grey color
represent Nspt values below 30 blows (which do not represent
trouble for the continuous flight auger equipments), the other
values follow with the presented colors showed sequentially in
Figures 3 to 5.
The slicing was done taking into account that the foundation
would start 4 meters below the original ground level and that
the foundation with continuous flight auger has a minimum
execution depth, which in the case was considered 8 meters
from the excavation, that is, 12 meters below the ground level
(4 meters of excavation + 8 meters of minimum length for
continuous flight auger piles).
It can be observed by such sequence of slicings that some
places of the construction had soil areas with low Nspt
resistance (values in grey color) which were in course and that
the design should consider such fact. By taking the analysis of
such problem that the idea of elaborating a bearing capacity
model for the construction came up, which was done. By
observing the great variability of the geological profile it was
evident that the resistant surface was variable forcing the
definition of different depths for each region of the construction
by the detailed analysis of the three-dimensional model.
However for the model to be convincing the over-position of the
calculate piles in the design was done in the bearing capacity
model
Figure 3. Horizontal Slicing Sequence of the Nspt Model
–
Decision
Taking for the Execution of the continuous flight auger piles
–
18 m
depth.
Figure 4. Horizontal Slicing Sequence for the Nspt Model
–
Decision
Taking for the Execution of continuous flight auger piles
–
19 m depth.
Figure 5. Horizontal Slicing Sequence for the Nspt Model
–
Decision
Taking for the Execution of continuous flight auger piles
–
20 m depth.
3.2
2D Sections of Bearing Capacity (tf)
Because of the application of the new technique, in the
beginning there was a resistance by the piling contractors
concerning the usage of the obtained results from the bearing
capacity models. Forcing the specialization of the majority of
the piles to make it easier to understand the decision taking in
terms of design level that were subsided by the bi and three-
dimensional models.
