Soldier Pile Walls
Soldier pile walls provide a core system for earth retention in both temporary and permanent applications. Structural “soldier” piles are installed from original grade. Then, as the site excavation proceeds in lifts, lagging is placed between the piles to retain soil. Soldier pile walls, supplemented with post-tensioned anchors or internal bracing form a very stiff shoring system, well suited for deep excavations adjacent to sensitive structures or facilities. Malcolm has constructed anchored soldier pile walls to depths exceeding 100 feet, and cantilever systems to over 25 feet.
A range of construction techniques are used for soldier pile installation, including conventional cased or uncased pile drilling, wet setting reinforcing into soil mix or CFA piles, or vibro-placement of beams. Site-specific conditions and constraints are evaluated in order to select the most appropriate and cost-effective system for each project. Piles are typically installed at 4 to 8 feet centers and extend at least 8 to 10 feet below final excavation grade to provide passive toe resistance. As site excavation proceeds in lifts, typically 5 feet in depth, lagging comprised of either wood or shotcrete is placed between the piles.
Each lagging and excavation cycle is repeated to the full depth of excavation. The soldier piles provide arching resistance which helps support the exposed soil face until lagging for each lift is completed. Although soldier pile walls can be constructed in most ground conditions, short lift heights or additional ground treatment may be required for pre-stabilization of exceptionally soft or loose soils. Dewatering systems can be combined with pile and lagging walls to allow excavation support in otherwise flowing granular soils below the groundwater table.
Most temporary walls use wood lagging. Soil is trimmed behind the front flange of the soldier pile then lagging boards are placed to bear against the exposed steel. For permanent walls, either pressure treated wood or structural shotcrete can be installed, anchorage systems are corrosion protected and any exposed steel is shop coated. When shotcrete is used, it is attached to piles using headed studs and fully encases the steel for corrosion protection. Malcolm offers a range of aesthetic solutions for the shotcrete wall finish including rod, float or “natural rock” sculpting and coloring.