Sheet piles are normally formed of reinforced concrete or steel;
Figure shows the various types of SHEET PILING available
Reinforced Concrete SHEET PILES
Reinforced concrete SHEET PILes are of value in the construction of permanent embankments to rivers, canals and other forms of water-related structures. The piles are suitably interlocked and the toes of the piles are shaped to facilitate easy driving and interlocking. The heads of the piles are cut down to the required level before finishing off by casting a capping beam. The concrete and reinforcement for the piles should comply with the current Code of Practice.
Steel Sheet Piles
Steel SHEET PILING is the most common form of sheet piling and is used in both temporary and permanent works. It is used in such structures as cofferdams, retaining walls, river frontages, quays, wharves, dock and harbor works, land reclamation and sea defense works. It has an advantage over other forms of sheeting in that it has high structural strength combined with water tightness and can be easily driven into most types of ground. These are interlocking and can be driven to depths which provide adequate cut-off to prevent piping (sub-surface boiling of soil due to water pressure) in water logged soils
Steel sheet piles are available in four basic forms
- Normal sections
- Straight web sections
- Box sections
- Composite sections or high modulus piles.
Normal Section Sheet Piles include the well-known as Larssen and Frodingham sheet piles. Larssen piles were named after an engineer who worked in Bremen at the turn of the century. He developed the principle of interlocking sheeting for temporary work. The sections were first rolled in one operation in the UK in 1929. The Frodingham SHEET PILE is the English name given to a section which was designed by Hoesch (a German company) as an alternative to the Larssen pile; it appeared in the UK in 1937. The sections are designed to provide the maximum strength at the lowest possible weight, consistent with good driving qualities. The interlocking of steel sheet piles facilitates ease of pitching (positioning the pile ready for driving) and driving; it also results in a close-fitting joint which forms an effective water seal. In some cases, however, the joints may be sealed by brushing a sealant into the joints prior to pitching, the sealant expands to many times its original thickness, thereby forming a watertight joint. A wide range of SHEET PILE sections is produced These sections are available in various grades of steel, including copper-bearing steel for increased corrosion resistance. engineers prefer the Larssen pile from a driving point of view, due to the uniform shape of the section. Slinging holes are provided in both types of sheet pile; the Frodingham piles have a 32 mm diameter hole located 75 mm from the top of the pile, whereas the Larssen pile has the lifting hole located 150 mm from the top of the pile. Frodingham sheet piles are normally supplied interlocked in pairs, which saves time in handling and pitching; Larssen piles are normally supplied as single piles.
Straight Web Piling is used to construct cellular . Such piles are interlocked and driven to form cells which are then filled with gravel or broken rock. The outward pressure of the fill material develops high circumferential tensile forces in the piling. The Frodingham straight web pile is designed to resist these forces by virtue of the shape of the interlock. This ‘cranehook’ shape gives a high tensile strength in the plane of the piling while at the same time permitting angular deviation between one pile and the next. The normal trough shaped sections are not suitable for cofferdam work, where tensile forces have to be resisted, because the interlocks are not designed for tensile strength and therefore would deform and open out when subjected to stress. Junction piles are provided to facilitate the jointing of the cells.
Box piles are formed from two or more sheet pile sections welded together. They are used where local heavy loads are anticipated and can be positioned in a normal section pile wall so that the appearance is unaffected. Box piles can be used as individual units for open jetties and dolphins where bending moments are high. They can also be used as bearing piles for foundation work.
Composite Sheet Piling or high modulus section piling has been developed to support bending moments which are in excess of the capacity of normal sheet pile sections. This is of particular importance in waterfront protection where larger ships need increased wharf height beyond the limit provided by Larssen and Frodingham sections. The ability of high modulus section piles to support large bending moments and heavy axial loads simultaneously makes them suitable for quays carrying heavy cranes and for permanent load-bearing abutment walls. Any of the larger Universal beams can be used together with any length of sheet pile to meet driving requirements and designed loading. The system produces a wall of identical units which can be produced in a range of sizes, giving optimum economy. Lightweight trench sheeting is used for supporting the sides of trenches and excavations, cofferdams in shallow depths of water and small retaining walls. The sheeting is available in lap-jointed and interlocking sections and is obtainable in standard lengths from 2 to 8 meters, in 0.5 increments.