INTRODUCTION
Sheet piles are produced in various sections and material specifications. The type of sheet pile section to be used is dependent on several factors.
Major design factors include the subsurface conditions, the type and depth of soil to be retained, the magnitude of the surcharge at the top of the retained side, the seismicity, and the design life of the wall. Other factors include the type of environment where the sheet piles will be installed, on whether the environment is highly corrosive or not.
The first type of sheet pile profile that we will look into is the U profile. By its name, U-type sheet piles are generally shaped similar to the letter U in the alphabet. In the Philippines, the U-type sheet pile is widely used by engineering consultants and contractors for various infrastructure projects.
Permanent installation of U-type sheet piles is commonly seen on retaining wall and floodwall/ flood protection projects, as presented in Figure 1. This type of sheet pile profile can also be used for temporary applications like braced and unbraced excavation protection systems.
Locally, U-type sheet piles are classified into three (3) types. These are Type II, Type III, and Type IV sheet piles. Type II U profiles are usually used for temporary excavations, while Type IV U profiles are used for permanent retaining structures with higher retained soil heights.
Apart from U-type steel sheet piles, Z-type sheet piles are also used for a lot of infrastructure projects. By its name, this type of sheet pile profile is generally shaped like the letter Z in the alphabet. Z-type sheet piles are interconnected at its top and bottom flanges to form a continuous wall. Usually, this profile is installed for ports, jetties, and other offshore structures.
Site conditions for offshore applications usually translate to larger design forces which have to be resisted by the sheet pile walls. Inherently, Z-type sheet piles are wider and have a larger depth, which would result to higher values for the moment of inertia, and the section modulus consequently. The section modulus is a geometric parameter of the sheet pile (or any structural element) that generally defines the flexural capacity of the chosen profile. Large bending moment capacities are usually observed for the Z-type sheet pile, and is much preferred to be installed where site conditions are quite challenging or unfavorable.
H SHEET PILE (HAT TYPE)
Similar to U-type sheet piles, H-type sheet piles are also U-shaped. This type of sheet pile profile, however, has a larger flange width as compared to the typical U profile.
This increase in flange width translates to a higher bending moment capacity of the sheet pile wall. The high bending moment capacities inherent to this sheet pile profile enables the designer and contractor to use this profile for project sites with relatively large forces present.
COMBINATION WALLS
The three (3) sheet pile profiles discussed in the previous sections can be installed together with different structural steel elements such as pipe piles and/or H (or I-shaped) piles. As sheet piles are installed with these elements, a combination wall is formed. A combination wall (or combi wall) provides better bending moment and shear capacities, which aid in resisting the forces present in the structure. When designed properly, a combi wall can serve as a more cost-effective solution as compared to a typical continuous sheet pile wall.
If you want to learn more about sheet piles and its design and application, you may get in touch with ESC Steel today. ESC Steel offers a wide range of products from sheet piles, structural steel beams and columns, and even marine mooring hardware and accessories. We are always happy to help you.