References
Industria Minerve
MONACO, 2008
Excavation with Berlin-type walls for the construction of 4 residential buildings with 267 parking places.
The Administration des Domaines de Monaco awarded the contract for building 4 residential buildings (148 apartments in buildings of 6 to 14 floors) over a surface area of 4,200m², with 267 parking places to the Monaco based SAMEGI property developer.
The Solétanche Sam/Alberti Sam consortium was appointed to provide the retaining walls and the excavation and foundation work.
Constraints
The excavation backs on to a slope, with six-storey buildings founded on spread footings just a few metres away. These features meant 2 constraints had to be factored into the construction survey:
- No possibility of using the surrounding subsoil to install long anchors
- Very tight restrictions as to allowable deflections on the retaining structure at the party walls (15mm for an excavated height of over 30.00m) of the neighbouring buildings.
Design works
The retaining wall varied in height from 8 to 35 m and was built using techniques geared to the different parts of the site:
- Berlin walls with piles of diameter 800mm, reinforced with an HEB 400 beam and connected by a 400mm thick shotcrete wall and temporarily supported by 6 layers of prestressed anchors and angled struts
-Miniberlin walls made up of micropiles (diameter 250mm) reinforced by steel pipes (diameter 177mm, wall thickness 20mm).
A comprehensive system for monitoring the structure itself and the neighbouring structures was established on the site. The system included inclinometers, topographic targets, load cells on the anchors and piezometers.
The Observational Method was applied in order to keep within the previously-established acceptable threshold deflections: measurements were taken at regular intervals and the results correlated to the projected calculations so as to make any adjustments that might be necessary.
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
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...
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