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Digging deeper – a review of South African practice on deep excavation design in urban areas

A survey was conducted to assess the current design practice of multi-anchored walls in South Africa and to evaluate

the need to incorporate certain topics in the revised SAICE Lateral Support Code of Practice in light of the adoption of Eurocode 7. The respondents’ answers to certain questions differed significantly from one another. This highlights that one of the major challenges in current geotechnical engineering practice is the lack of and inconsistent use of geotechnical design codes or design methodologies in South Africa.





Substantial reliance is placed on intuition and past experience in similar geological profiles to choose an appropriate system, possibly as a result of the poor standard of subsurface investigations. These systems normally comprise either soil nails or multi-anchored soldier pile walls.

Various analysis methods are used to assess anchor forces, with most respond-ents using apparent earth pressures (AEP) to estimate required anchor forces, and both BOE SSI methods and FE analysis to assess structural forces in piles and displacements. A parametric study was undertaken to establish how ground an-chors, if not prestressed during installation, would attract load in a staged excavation using both BOE and FE with significantly higher loads attracted to lower anchors.

Prestressing ground anchors to 80% of the design FHWA loads resulted in similar loads and bending moment diagrams between Winkler spring and FE solutions. Special attention should be paid to deeper excavations with multiple bracing levels, where conventional analyses may severely underpredict wall bending moments. In such cases, Winkler spring and FE simula-tions are strongly encouraged in addition to the conventional analyses.

Read more by downloading file:

Digging deeper – a review of South African practice on deep excavation design in urban areas

F. H. van der Merwe, and D. Konstantakos 2020. SAICE






SAICE Civil Engineering April 2020 DiggingDeeper FINAL for Frans
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