Gravel filling of Cellular Box Caissons
| The study provided for the gravel filling of the back caisson cells. |
The construction company argued that gravel filling of the back cells only would result in:
- Differential settlements and inward turn of the caissons.
- Non-observance of the alignment.
- Problems in the construction of superstructures and installation of bumpers
due to the non-observance of the alignment.
The solution proposed by the contractor was the simultaneous gravel filling of all caisson cells; however, it was not accepted due to cost concerns. The result was undesirable. Deflections from the alignment of the front were on the order of 30 cm.
Caisson landslides
The construction company had underlined the risk
of increase of the reflection factor, which would lead to the increase of
the hydrodynamic pressures on the caissons.
The supervising office of the Ministry of Public Works followed consultant
and insisted on the initial foundation level at -11.00 m. The answer to
the problem was given by the absorbent front, which provided, initially
in the studt, a reflection factor equal to 0.35. The modified absorbent
front with the addition of 2 additional rows of holes, combined with the
internal holes (as presented in the hydraulic
study) the 0.60 m settlement led to a reflection factor of 0.40, a value
that was initially provided by the initial study.
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