Sheet Pile Design

In the analysis of a sheet pile design the two principle factors that need to be clearly defined are the structural requirements of the retaining wall and as to whether it is permanent or temporary, and the underlying ground conditions at the site of construction.

The selection of the type of wall – cantilever, anchored or internally supported will depend upon the function of the structure, the underlying ground conditions and the proximity to any existing building which may influence the loading of adjacent surfaces.

In a sheet pile design a cantilever wall will generally be used where the height to be retained is low as the strength is derived solely from the ground conditions into which the sheet pile is driven. Typical applications are in permanent works flood alleviation schemes along either canal or river banks. As a guide the overall length of pile that can be used in cantilever can be at the ratio of one third retained height to two thirds embedded in the ground. Thus for a 3m retained height a suitable 9m length of pile could be considered. Further design calculations should also be made in order to determine the deflection of the pile head and as to whether the movement at surface level is acceptable.

An anchored retaining wall would be selected where retained heights are greater or when the potential for pile penetration may be limited by the prevailing ground conditions. Again the most suitable sheet pile section should be based upon a combination of the structural and buildability requirements. The use of anchors in a sheet pile design will limit surface deflection, and permit a shorter length of pile to be used. However, difficulties may be experienced in obtaining access easements for the anchors under adjacent structures. The drilling and installation of ground anchors is expensive and would have construction programme implications.

Where a series of sheet pile walls interlock to form a closed cofferdam structure, internal supports may be incorporated in the sheet pile design and construction in order to provide a stable structure within which construction may be completed. The cofferdam structures are more typical of temporary works applications.

This article comes from volkergroundengineering edit released