Support Systems for Deep Excavations
The term excavation support refers to an engineered solution designed to stabilize an excavation. An excavation support is generally required for excavations that exceed a depth of 6 ft, or excavations that are not sloped. Support for deep excavations (depth exceeding 10 to 14 ft ) refers to the additional bracing that is required to stabilize a retaining wall such as a sheet pile . Such excavation support systems comprise tiebacks, cross-lot steel struts, rakers, helical anchors, and top-down concrete slabs.
The role of a support system in an excavation is to provide lateral bracing for the retaining walls. Support systems can be subdivided into external and internal, depending on the load transfer mechanism. External supports (namely tiebacks) work by transferring lateral excavation loads beyond the active zone of soil movements (retained side). On the other hand, internal supports such as struts, rakers, or floor slabs, transfer lateral loads within the excavation (across opposing walls or to other internal structures). In all cases, support and retaining systems have to work closely together in order to guarantee a high level of performance.
The following image illustrates the rock anchor excavation support system used in the World Trade Center in New York.
Who should design Support of Excavations?
Excavation support design is a very sensitive task. An excavation support system should be designed by a licensed professional engineer that has very good understanding of soil and structural behavior. Excavation design requires geotechnical and structural knowledge. Experience always helps! The excavation support can also be designed by the contractor's engineer.
Support of Excavations and Software
The use of an advanced software program can prove valuable for the design of any retaining wall system. Our superior deep excavations design software - DeepEX - allows the design, evaluation and optimization of any excavation model in minutes, allowing the users to check different alternatives with different design methods. This can lead to economic and safe solutions!
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In the page section below you can find useful information (e.g. construction process, advantages, disadvantages ) regarding the analysis and design of several retaining systems commonly used in deep excavations.
Retaining walls with no supportsLearn More
Retaining walls with tiebacks & rock anchorsLearn More
Cofferdams - Cellular Cofferdams
Cofferdams with steel struts & walersLearn More
Braced Excavations - Cross Lot
Retaining walls with steel struts & walersLearn More