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| Diaphragm Wall Casting |
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Diaphragm walls provide a water tight barrier and are constructed with a minimum backslope subsidence. They are formed from reinforced concrete and are constructed as normal cast-in-place walls with support which becomes part of the main structure. The slurry trench method is commonly used which
involves the excavation of alternating panels along the proposed wall
using bentonite slurry to prevent the sides of the excavation collapsing.
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| The installation starts with the construction of shallow concrete or steel guide walls. The excavation is then made using special equipment, such as the thin-grab clamshell (fig. A). Bentonite slurry is then pumped into the trench to provide temporary support (fig. B) and a prefabricated reinforcing cage is lowered in (fig. C). The bentonite slurry is then replaced by concrete (fig. D) and the sequence proceeds onto the next panel. | ||||
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Diaphragm walls can be considered to be impervious and therefore the de-watering of granular soils is often neglected. However care must be taken to ensure that there are no openings or joints since they may result in sudden loss of soil. | |||
| Diaphragm
walls of shallow depths are often left unsupported since they are classed
as semi rigid structures. However for deeper excavations support is required
to restrict lateral deflections. |
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| Diaphragm
walls are ideal for soft clays and loose sands below the water table where
there is a need to control lateral movements. However they are relatively
costly. They are also unsuited to strong soils conditions where penetration
is slow and difficult due to the use of the slurry trench method. |
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| Diaphragm Wall Coasting Project | Special Foundation Construction | |||
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