Timber Posts Mean?
Timber posts are lagging used for retaining structures that support excavation where they run deep. Before excavation, soldier piles are placed and as excavation proceeds, timber lagging is placed between the soldier piles. In places where sloping or benched excavation is not possible soldier piles and lagging walls are a good option.
Compared to other types of retaining walls, soldier pile and lagging walls are inexpensive, easy and quick to install and allow for adjustments.
Trenchlesspedia Explains Timber Posts
Trenchless methods such as microtunneling and pipe jacking require launch and exit pits to be excavated for placing people and equipment. Timber lagging is positioned between the soldier piles as excavation proceeds. 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 high water table.