Fundamentally, retaining walls are used to change the elevation of the surrounding landscape. In highway construction, this is done for a variety of reasons. Wing walls coming off of bridge abutments are used to control the slope adjacent to the road and protect the abutment from scour. Retaining walls are also used to widen roadways in both cut and fill situations. Roads approaching overpasses need retaining walls to support the fill underneath the road. Different types of retaining walls and soil conditions require different solutions.
Sheet piles can take heavy vertical loads and are a very versatile product for both temporary and permanent retaining walls. One of their biggest advantages is the speed at which they can be installed. The vertical load capacity of a sheet pile would be similar to that of an h-pile or pipe; there is no difference in the stress calculation. Please note that because sheet piles usually carry high bending loads, it is recommended that the designer check the combined stresses. If the stresses or deflections are too high, sheet piles can be anchored with tie rods or grouted anchors. In temporary cofferdams, the sheet piles can be braced. Properly designed and protected steel sheet piles can meet design lives of 75 or 100 years. Pre-drilling can help facilitate the installation where driving conditions are especially hard.
Beam and lagging walls are an excellent choice where driving is hard. H-piles can be driven into very hard soils or dropped into holes predrilled into bedrock. Spacing the piles further apart reduces the amount of drilling that would have to be done, but increases the required size of the beam. Beam and lagging walls are one of the least expensive types of temporary retaining walls and can be built with h-piles or other beams. Like sheet piles, they can be anchored, but only the beams need to be anchored so a waler is not always needed. For permanent walls, concrete panels can be used in place of the wooden lagging.
Soil nail walls are built with threaded bar and work very well in cut situations. The nails and bars are drilled and grouted into the soil and interrupt the failure plane of the soil. Soil nail walls are built as the ground is excavated so the soil needs to have apparent cohesion. These types of walls can be especially useful for road cuts in hilly terrain.
Beams can also be used in secant pile walls. Secant pile walls are overlapping drilled concrete piles with a beam placed in every other hole for strength. They are very good if low noise and low vibration are required since there is no pile driving, only drilling. Secant pile walls cannot be used on a wall that is being backfilled, but are fine in almost every other situation. As with other wall systems, grouted anchors can be used to support secant pile walls.
Skyline Steel has a wide variety of products that can be used to build many different types of walls.