Construction of containment bunds

Natural slope angles of fill after hydraulic placement are usually (very) gentle. These slopes will depend on the placement method, the particle size distribution of the fill and the exposure to waves and currents, see Table 6.1. Should the fill not be contained by bunds, large volumes of fill may be deposited outside the actual footprint of the reclamation area. 

By eonstructing bunds and profihng their slopes to their required stable slope angle, it is possible to limit the volume of fill. In general it can be stated that with increasing coarseness of the bund material the slopes can be constructed at steeper angles. 

If the subsoil of the reclamation area consists of soft material having a low shear strength, a stable bund around the perimeter of the area may help to improve the stability of the fill. This bund can be constructed on top of a sand filled trench cut down to more competent strata. This construction method can prevent the need for entire removal of the soft strata or the construction of very gentle slopes. 

At a partly closed or open fill area, which lacks bunds at one or more sides, the 

If the bunds are sufficiently watertight and stable it may be possible to raise and control the water level within the contained area by adjusting the level of the overflow of the weir boxes. This may affect the settling regime of the fill and in particular of the fines, see also section 6.7.2. It might also be a solution to create sufficient water depth to allow for floating equipment like a spreader pontoon in the reclamation area. 

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For the first hft in the construction of containment bunds, frequently local soil is used. Moderate compaction (e.g. by a bulldozer) might be required to prevent the creation of more permeable zones which may soften during subsequent fill lifts. 

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