References
Larvotto hotel complex
MONACO, 2003
Deep foundations constructed on a quay reclaimed from the sea which comprised loosely placed larger rock ballast to form the embankment.
The “LARVOTTO hotel complex” site is situated on the LARVOTTO quay in MONACO, at the edge of the Franco-Monacan border. The site is accessed via Avenue Princesse Grace.
The site area is around 5 hectares on which the Monte Carlo summer Sporting is already built. The project fits into the eastern part of the peninsula, across the entire north to south length covering an area of 23,000m2.
Description of the works
Lot 3B - Foundations - comprising a diaphragm support wall in the western part, the general earthworks and the deep foundations : support piles under the hotel area, piles under the parking areas and micropiles in the critical areas and those difficult to access.
Site geology and geotechnical difficulties
The stratigraphy of the terrain encountered is as follows :
- Very open quay surface ballast composed of limestone blocks and massive rock fillings of +1.50 NGM to -12.00 NGM average.
- Sands and Gravels over 8 to 10m.
- Marno limestone substratum consisting of the cretaceous era which was utilised for anchoring into.
Diaphragm wall works
The first work phase consisted of erecting a support wall composed of micropiles produced by the ODEX method with permanent casing to drill through the difficult terrain.
The HA32 anchor rods were produced with bags in their fixed length to minimise slurry losses through the ballast during grouting. The B25 sprayed concrete was produced by a dry process after installation of a reinforcement composed of welded mesh panels.
Foundation support pile works
After removing the large blocks and pre-treatment of the open embankment material by injection, guide walls of large plan dimensions were fabricated in order to provide :
- A good reserve of drilling mud (loss compensation),
- passage during the rock filling drilling of more than one meter.
The support piles were produced using two mechanical grab appliances by means of heavy drill bits to destroy the large top limestone blocks and provide the anchoring in the cretaceous limestone.
Foundation pile works
Considerable resources were employed to perform the preliminary material removal over the first 14 meters. The blocks were destroyed according to areas either by drilling protected by vibro-sunk casings or by recess drilling at right angles to the supports with down-hole hammers and special reinforced augers. The piles were then produced using 2 Starsol 12000 piling rigs and 1 Starsol 20000 piling rig for the 1,0m diameter piles at 24m depth.
Techniques
A ground anchor is a load transfer system designed to transfer the forces applied to it to a competent stratum. An anchor is said to be temporary if it has a lifespan of under two years and permanent if the lifespan is over two years.
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.
A retaining shell is a slim shell structure used during vertical excavations. Unlike retaining walls, the weight of a retaining shell has little effect on its capacity to balance the pressures.
Ouvrages
Suitable foundations are required for all building and civil engineering structures to ensure that they perform within the settlement criteria established in the design of the structure. Special foundations are used where shallow footings do not provide adequate support for a structure.
Major urban excavations are one of the specialist activities of Soletanche Bachy. Such excavations are required for basements to buildings that are usually part of the foundations of the structure and also used for under-street car parks, cut and cover tunnels for roads, rail, metro and storm water tank...
Voyage au coeur de l'ingénierie de pointe
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