References
Vincom Block B
VIETNAM, 2008
Diaphragm wall and barrette works for the first six-level basement project in Vietnam.
Vincom Block B project is a 28-storey building and part of Vincom Ho Chi Minh City Complex which is located in one of the “Golden Land” areas in downtown Ho Chi Minh City - Vietnam. Encompassed by the main avenues Dong Khoi, Le Loi, Le Thanh Ton, Nguyen Hue and Ly Tu Trong, the 20,500m2 captured project will serve as a luxurious complex with a 6-level basement underground, the deepest basement ever built in Vietnam. Bachy Soletanche Vietnam’s scope of work consisted of 19,498m2 Diaphragm Wall and 132 nos. shaft grouted barrettes. Two sets of KS and two sets of KL grabs were mobilized to stick to a committed schedule of 21 weeks.
Diaphragm wall
The first step was to build a 1.2m thick diaphragm wall, down to a 49.7m depth for the future six-basement excavation. The water table level is 6.1m below ground level. The 93 panels were executed in 2 months.
Shaft grouted barrettes
Two static load tests were carried out to prove the effectiveness of shaft grouted barrettes. Shaft grouting improves friction enhancement when deeper foundations are required. Shaft grouting is performed through tube-a-manchette previously installed into the steel cages. One test was carried out on a plain barrette and one on a shaft grouted barrette with the same size at 2.5 times working load. After the test, shaft grouted barrette option was preferred by the client and only shaft grouted barrettes were realized after earth moving.
130 nos. kingposts (plunged stanchions) were then installed, at a maximum depth of 22.7m, to serve as temporary columns for “top-down” construction method. Removable steel beams were used.
Techniques
A diaphragm wall is a reinforced concrete wall that is made in situ. The trench is prevented from collapsing during excavation, reinforcing and casting by the use of supporting bentonite slurry. The slurry forms a thick deposit (the cake) on the walls of the trench which balances the inward hydraulic forces and prevents water flow into the trench. A slurry made of polymers can also be used.
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...
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