Some of the oldest forms of retaining systems used in deep excavations are Soldier Piles and Lagging Walls. These have effectively been used since the late 1800’s. Lagging and steel piles are used, and as an alternative, concrete pile, caissons, or circular pipes may also be used as Soldier Piles, but with an added cost. Timber Lagging is usually used but reinforced concrete panels may also be utilized for lasting conditions. Lagging walls and soldier piles are fashioned by creating soldier piles at regular intervals (typically 2 to 4 meters), exhuming in small stages and installing Lagging, and backfilling and compressing the void space behind the Lagging.
Moment resistance in Soldier Piles and Lagging Walls is offered exclusively by the Soldier Piles. Passive soil resistance is acquired by inserting the soldier piles underneath the excavation grade. The Lagging bridges, keeping soil across piles and shifts the lateral load to the Solider Pile.
Soldier Piles and Lagging Walls are the most reasonably priced systems in comparison to other retaining walls. They are also very quick and unproblematic to construct. The main shortcomings of Lagging systems and soldier piles are that they are usually limited to temporary construction, they cannot be used in high water table situations without vast dewatering, inadequate backfilling and associated ground losses can result in major surface settlements, they’re not as stiff as some retaining systems, and because the extension of a soldier pile is implanted beneath sub grade, it is very complicated to control basal soil movements.