Permanent system overview
While most soldier piles and lagging walls are used to temporarily retain soil in an excavation site, temporary lagging walls can become permanent when the soil needs to be retained for at least 36 months, according to current Washington state law. The most important consideration when installing a permanent lagging wall is that soil conditions are suitable. The retained earth cannot be prone to shift easily (such as with sand or soft clay) or have a high water table. For areas that may experience large amounts of precipitation, lagging walls must be built to drain water away from them, as weeping holes built into the wall aren’t sufficient.
Lagging wall materials
Permanent systems must be strong and resilient to corrosion, so the lagging walls are typically made from pressure-treated wood or concrete, and any anchoring or exposed steel is coated to protect against corrosion. This includes soldier piles and tiebacks embedded in the soil. Timber lagging material can last up to 20 years. Permanent lagging walls can also be made from precast fascia panels. Fascia panels are typically made from concrete and can have a lifetime of up to 75 years. Fascia panels are strong enough to carry the full load of retained soil if the timber lagging behind it fails.
installing permanent lagging walls
The lifetime of a timber lagging wall can be increased if a fascia panel is added and if the lagging wall is visible for inspection. Adding a fascia panel to a lagging wall is common for large excavations, where the lagging walls help keep the excavation site clear for workers to construct the deep foundation. The foundation is later integrated with the fascia-paneled lagging walls.
Contact Pearson Drilling today to learn more about how permanent lagging walls and soldier piles could suit your constructions needs!