Soldier Piles and Lagging

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Definition - What does Soldier Piles and Lagging mean?

Soldier piles and lagging is a technique where vertical steel piles are inserted into the ground around the excavation perimeter before excavation is started. When excavation is started horizontal lagging sheets are installed behind the piles that act as a resistance barrier to the soil behind it.

This transfers the weight of the soil against the lagging to the steel piles. Lagging sheets can be made of wood, steel or concrete. Soldier piles are either driven into the ground or lowered into an excavation and grouted.

Timber lagging is positioned between the soldier piles as excavation proceeds.

Trenchlesspedia explains Soldier Piles and Lagging

In the soldier pile and lagging technique, the lagging is able to resist the load exerted by the retained soil by transferring it to the soldier piles. For shallow excavations, the walls can be made as a cantilever, and for deeper excavations, additional supports in the form of tie-backs, bracing or lateral supports can be provided.

However, this system is mostly limited to temporary construction and is difficult to use in places with a high water table. Soldier pile and lagging walls are retaining structures used for the purpose of supporting excavation, especially where excavations run deep. Piles made of steel, and lagging made of timber is typically used, however, caissons, concrete, and circular pipes can also be used.

Where lagging is to be permanent concrete panels can be used instead of timber. Compared to other types of retaining walls, soldier pile and lagging walls are inexpensive, easy and quick to install and allow for adjustments.

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