Sheet Pile Walls
Sheet piles are structural sections that can be interconnected to form a continuous sheet pile wall. Sheet piles rely on their structural stiffness to resist lateral forces due to earth, water, or other loads. While different types of sheet piles are available, steel sheet piles are the most common in modern construction. The following paragraphs describe the main types of sheet piles with their relative advantages and disadvantages over other types of sheet piles.
Steel Sheet Piles
Steel sheet piles are the most common types of sheet piles used. Modern steel sheet piles comes in many shapes such as Z sheet piles, U sheet piles, or straight piles. The sheet piles are interconnected with a male to female joint. There are many different types of sheet pile connections each with their own advantages or limitations. At corners, special junction joints are utilized to connect one sheet pile wall line to the next. The main advantages of steel sheet piles over other sheet pile types are:
a) Wide range of product availability
b) Increased strength
c) Durability when corrosion is not an issue
d) Can be utilized in heavy civil construction
The main drawback of steel sheet piles versus other sheet pile types is that corrosion protection is required in highly corrosive environments. Also, with the exception of precast concrete sheet piles, steel sheet piles are more expensive.
Timber Sheet Piles
Timber sheet piles typically consist of timber planks that are interconnected with a tongue and groove joint. Different types of timber sheet piles include simple planks, Wakefield timber sheet piles (when many planks are nailed or glued together to form a single timber sheet pile section), tongue and groove timber sheet piles, or splined timber sheets. Timber sheet piles are seldomly used in modern heavy civil construction. Their most common application today is in relatively shallow excavations for utilities when groundwater is not present. Timber sheet piles could potentially be used in long-term or marine environments when the timbers are properly treated. However, their durability would be questionable.
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Vinyl Sheet Piles and polymeric sheet piles
Vinyl sheet piles are quite similar to steel sheet piles but are fabricated from synthetic materials. They are ideal for small environmental barriers or sea-front projects where there is a small exposed height. Vinyl sheet piles are commonly used as erosion protection barriers. Depending on the type of synthetic sheet pile material that is used, vinyl sheet piles can perform differently under long term exposure to sunlight or chemicals. Vinyl sheet piles have smaller yield strengths and are less stiff when compared to steel sheet piles. An engineer specifying vinyl sheet piles should consult with the individual manufacturer regarding any restrictions or applicability of using a specific product.
Aluminum Sheet Piles
Aluminum sheet piles work similarly to steel sheet piles in provide resistance. Aluminum strengths can vary from 8ksi to 45 ksi, and some aluminum materials exhibit considerably different tensile yield and maximum yield strengths. Aluminum has a modulus of elasticity of 10000 ksi, approximately 30% of the value of steel. As a result, aluminum is considerably more flexible than comparable steel sheet pile sections. Aluminum sheet piles on the other hand are lighter than steel and offer improved corrosion resistance in marine environments. For this reason, aluminum sheet piles might be ideal in some marine applications.
Aluminum sheet piles may corrode in acidic soils or if placed directly against marine treated lumber due to the fact that the lumber has a high concentration of copper, chrome and salt. This problem may be solved simply by placing a membrane between the lumber and the aluminum.
Precast Concrete Sheet Piles
Precast concrete sheet piles are constructed by casting reinforced concrete panel sheets with tongue and groove or fillable joint at the sheet pile ends. Precast concrete sheet piles are relatively uncommon and might be used when steel sheet piles are not available or under very special conditions. They can offer substantial stiffness and strength capacity but require extensive labor to fabricate, care to transport and handle. Because of their increased thickness and tip area, precast concrete sheet piles can be very hard if not impossible to drive. Precast concrete piles might also experience tension cracks during driving as driving tension stresses travel through the section.