Steel piles can be drilled into the ground for temporary or permanent purposes, or used as temporary structure in buildings*. One of the most widely used purposes of piles is soil or water retention. For example, if a building site needs soil dug out of a fairly large hole in order to layout the foundation, the steel piles are placed to hold the soil back. If a bridge over water needs repairs to it’s foundation, piles are placed to keep water out of a small area so the bridge structure can be worked on. Similarly, if a beach is in danger of damage from hurricanes and storm surge, the piles are driven as a seawall along the beach to prevent sand from washing away and compromising beachfront building structures. Piles are fabricated in different steel grades to meet the needs of the project, such as soil composition, depth, and loads.
Piles can be ordered in different shapes and configurations, such as Z-shape formed sheet (shown in the image above), flat sheet, steel tube, or shaped I-beam (known as a W-shape). Some of these shapes have connectors on the piles, some do not, but are able to have connector piles welded on. For example, small connectors can be added to steel tube to connect to Z-shape piles, to form what is called a combination wall. Also, steel sheet piles are either hot rolled (custom formed), or cold rolled from other steel shapes to create the sheet pile. The image above shows a cold rolled system.
The shapes of the walls themselves can be aligned with virtually any desired perimeter. This is made possible by degrees of tolerance in the interlocks between piles and corner conditions that can be created in one of three ways: connector piles (as noted above), fabricated (or bent) corners, or no direct connection from one pile to the next.
The length that steel piles should be produced is based on a few factors. The maximum length that piles can be shipped depends on each company’s production and shipping abilities. The site also needs to be analyzed for bedrock location in some situations. Steel piles would bend and/or break if drilled into bedrock. Once this is mapped out, engineers can analyze this and forward length requirements to a steel company. (Some steel companies have certified PE’s on hand just in case). Also, the contractor needs to decide how much steel will be above ground level. Having steel piles sticking up from the ground is unsightly in publicly used spaces, so one avenue to take is covering the steel with soil (if piles are permanent). Another way to deal with the look of permanent steel is to cut the piles at certain lengths. Sometimes the walls have a concrete cap to clean up the look of the wall, in which the piles are either cut at one length or multiple lengths to achieve this.
Associated Structural Elements
Geo-structural steel increases the strength of the wall. A system comprised of C-channel, threaded bar, bolts, and plates works together to keep the wall in place. Other accessories include points, protectors, or “shoes” to put on the bottom, or tip, of the pile for drilling, and splicers (to put two lengths of steel together, end-to-end to form 1 longer piece of steel).
*This post is only an abbreviated overview to help in understanding what steel piles are, as there is a wealth of information around the web.