Internal Bracing

Internal bracing begins with steel members (typically beam or channel sections) known as walers. These members are installed along the perimeter of the earth support system, and can either be segmental or continuous. Depending upon the footprint and depth of the excavation, the horizontal components of support can be provided by a combination of cross-lot braces or struts, corner braces, and/or rakers. Struts and corner braces are installed along the same plane as the walers, while rakers are connected to the waters, installed downward at an angle, and often anchored against “heel blocks”. Internal braces can be pre-loaded if desired, or can simply be loaded as the excavation progresses.

The use of internal and external bracing depends on several factors. External bracing is often more desirable from a construction standpoint, as it enables more freedom for excavation and construction within the ESS. However, issues of easements, utilities, and nearby underground structures must be carefully examined and evaluated before selecting tiebacks for a given project. Internal bracing also presents its own set of concerns, including a much greater impact to related trades (including excavation and concrete subcontractors), and therefore can add considerably to the overall duration of a project.

Support of Excavation with Corner Braces