Soldier piles and lagging walls are used primarily for temporary excavation support. These walls are constructed by installing vertical soldier piles, typically H beams, from the original grade before excavation begins. The excavation is performed in lifts of 4' to 5' so that the timber lagging can be installed between the soldier piles to restrain the soil.
What Are Soldier Pile Walls?
Soldier piles are steel I-beams driven into the ground to help with soil retention. Soldier pile walls are ideal for sites that aren’t conducive to excavation, such as for geogrid walls, cantilever walls and other retention techniques.
Advantages of Soldier Pile and Lagging Walls
Lagging walls are among the least expensive retention systems. Soldier piles can be installed quickly and lagging walls are fast to construct. This technique is versatile and allows for adjustments in the field if necessary.
How Are Lagging Walls Installed?
Soldier piles are typically driven into the ground 2 to 4 meters apart prior to excavation. Horizontal lagging is inserted behind the H piles as the excavation progresses. Lagging walls can be constructed with pressure-treated timber lagging, steel lagging or precast concrete lagging. Anchors or bracing may be used to reinforce the lagging. Steel beams called “whales” extend between piles to reinforce a lagging wall.
Soldier piles are commonly used when soil conditions aren’t suitable for other types of wall construction. Consolidated clay, soils above the water table, and soils that can be drained of water are typical. Unsuitable soils include soft clay or sands.
Soldier piles can only extend 12 to 18 feet above the soil line before the load becomes too great to support. They’re typically limited to temporary construction and can’t be used in high water table conditions.