Civil Engineering April 2021 | Vol 29 No 3

Civil Engineering April 2021 35 The first two parts of this series of articles* (van der Merwe & Konstantakos (2020) and van der Merwe & Parrock (2021)) provided feedback on the design practice followed by different geotechnical engineers for the design of deep basement excavations in South Africa. This forms part of a survey that was forwarded to respondents as part of the updating of the SAICE Lateral Support in Surface Excavations Code of Practice. Part 3 of this series will address issues such as the use of stressed self-drilling hollow bar grouted anchors, anchor and soil nail corrosion considerations, the use of non-prestressed soil nails in embedded piled walls, seismic loading, limit on crack widths in concrete pile sections, and typical failures or disputes that have arisen in South Africa. SELF-DRILLING ANCHORS/ HOLLOW-BAR ANCHORS The following questions were asked to respondents: If you cannot install conventional strand anchors due to a profile that collapses during unsupported drilling, do you consider hollow bar self-drilling anchors (SDAs) as a feasible alternative? The use of temporary cased drilling is often considered to be too time consuming and expensive. This can be Digging deeper – a review of South African practice on deep excavation design in urban areas | Part 3 Frans van der Merwe Pr Eng PrincipalGeotechnicalEngineer,CityofCapeTown Chair, Working Group updating SAICE Lateral Support in Surface Excavation Code of Practice frans.vandermerwe@capetown.gov.za Alan Parrock Pr Eng Consultant/ Specialist Engineer ARQ alan@arq.com Fernando Pequenino Pr Eng Principal Geotechnical Engineer GaGE Consulting fernando@gageconsulting.co.za Figure 1 11 m deep excavation in Oranjezicht, Cape Town (Courtesy of L Celliers, Kantey & Templer)