Sheet pile cutoff wall is used in all types of water retaining structures to reduce the exit gradient at the downstream toe and prevent the chances of sand boiling and piping.
It is used for excavation bracing and dewatering applications. It can be made of wood, reinforced concrete, or steel, with steel being the most effective material for constructing a ground-water barrier; it also has many types, like u section sheet piles and z section sheet piles The construction of a steel sheet pile cutoff wall involves driving interlocking sheet piles down through unconsolidated materials like soft soils and other tight spaces to a unit of low permeability.
For a quick estimate the material is usually driven 1/3 above ground, 2/3 below ground, but this may be altered depending on the environment. Taller sheet pile walls will need a tie-back anchor, or "dead-man" placed in the soil a distance behind the face of the wall, that is tied to the wall, usually by a cable or a rod. Anchors are placed behind the potential failure plane in the soil.