References
Quai Carnot - Concarneau Harbour
FRANCE, 1998
Reinforcing a quay wall with reinforced Jet grouting columns (double Jet).
Quai Carnot was built between 1932 and 1937. It is made up of two superposed, prefabricated block beds, topped by a concrete wall. The structure is set on rocks, lying on clayey soil, with mediocre geotechnical features.
Problems
The western section of Quai Carnot has been is subjected to major disorders since the end of the Eighties: sliding block beds, tipping towards the basin and face distortion.
Since 1990, this structure has progressed more than one metre in its centre.
In 1991, this fishing boat quay was closed to commercial operations.
In 1992, the quay magistral moved by several centimetres in a month, in several places.
Temporary work (rock cramping, platform coating) was performed to stop damage.
In order to reopen the quay for commercial enterprise, reinforcement work was performed in 1998.
REINFORCEMENT WORK
Included mainly Jet grouting columns, micropiles and pins.
Jet grouting work
A succession of Jet grouting columns, 1 m in diameter, set out every metre.
These columns are 6 metres long and enable to distribute load in depth, in a soil with better features.
They were sunk after Ø 250 preboring of quay was performed.
When work began, test columns were produced in order to define treatment jetting parameters.
Micropiles
Where each jet column stands, the quay and Jet grouting treatment were redrilled in order to produce micropiles, by embedding a 12-metre long thick pipe (Ø 153-178) in each bored hole.
Pinning blocks
Pinning of quay blocks was performed every 150 metres by embedded HA 40s, in 80-mm diameter perforations.
RESULTS
After dredging the temporary foot abutment and stabilisation, the quay returned to service at the end of 1998.
Techniques
Jet grouting is a construction process that uses a high-pressure jet of fluid (generally 20 – 40 MPa) to break up and loosen the soil at depth in a borehole and to mix it with a self-hardening grout to form columns, panels and other structures in the ground. The parameters for the jet-grouting process and the desired final strength of the treated soil depend on a number of characteristics, such as the soil type, the technique used and the objective to be reached. In granular soils, the high-pressure jet breaks up the grains through erosion, while in a cohesive soil, such as clay, the jet breaks the mass up into small particles. High pressure is needed to produce the kinetic energy required for the jet through a small-diameter nozzle. Waste material from the process (a mix of soil, water and binder) is recovered at the surface before being taken away for disposal.
A pile is a structural element driven into the soil for transferring loads and prevent deformation. Its slenderness ratio is not limited.
Pile shafts can be uniform and rectilinear, telescopic and belled out.
Piles can be installed either separately or in groups. They can also form a retaining wall, a mixed curtain wall, contiguous piles, secant piles and composite curtain walls, such as Berlin walls and similar. Piles are also used as precast beams to be placed in the structure of the building they support.
Ouvrages
Voyage au coeur de l'ingénierie de pointe
Find out more about our expertise by:
