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104 Aeroton Road, Aeroton Ext. 2

P.O. Box 38041, Booysens, 2016
Gauteng, South Africa.

Tel: 011 226-8400
Fax: +27 11 494-1604

279, Rua Dar Es Salaam, Maputo,

Tel : +258 21 493 392
Fax: +258 21 493 393

Plot 1329, Independence Avenue, Kitwe

Tel: +260 212 213 377
Fax: +260 212 218 833

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Slurry Cut-off wall works


Coega Harbour
South Africa

Client : National Ports Authority
Main Contractor : Ngquara Harbour Contractors
Consulting Engineer : Jones And Wagner
Works Carried Out: : Slurry Wall - 30 000m2
Date Of Works : January 2003 - April 2003

Main Quantities

  • Excavation of slurry cut-off wall to a maximum depth of approximately 27m
  • Plan length of approximately 1300m
  • The largest slurry cut-off wall project to date in Southern Africa
  • Required 24-hour site operations running six days a week
  • 3600m hydraulically operated Kelly bar guided KS clamshell grab as well as two 2700m KL mechanically operated rope suspended calm shell grabs.

Southern Africa's largest self-hardening slurry cut-off wall is the key to Ngqura's success.

Between December 2002 and Pril 2003 Dura Soletanche Bachy completed the first phase of a 30 000m2 single-phase self-hardening slurry cut-off wall as part of the geo-technical package of works for the NGQURA (Coega)Harbour Project Development near Port Elizabetg, Republic of South Africa.

The challenge was to construct a high quality slurry cut-off wall with very low specified permeability in an extremely fast-track programme. In order to do so, Dura Soletanche Bachy introduced the latest high-tech innovative geo-technical programme. In order to do so, Dura Soletanche Bachy introduced the latest high tech innovative geo-technical plant and methods.  The projects was successfully completed within the construction programme.

The slurry cut-off wall was installed in order to intercept two aquifers, the upper one being silty sand and the lower one being a layer of large pebbles (averaging approximately 3m thick) at depths between 20 and 25m and finally to form a sealing key into the underlying soft rock mudstone layer.

Although commercially only a small value of works in comparison to the project as a whole, the slurry cut-off wall works were absolutely crucial to the overall success of the chosen construction methodology, both in terms of construction programme as well as the cut-off wall’s technical performance, with both of these factors being critical. NHC therefore selected Dura Soletanche Bachy on the basis of the formidable track record, experience, knowledge and specialist resources.

Having completed the slurry cut-off wall, excavated and constructed the cast in-situ gravity retaining walls that form the new quay walls, a total of approximately 13 million cubic metres of earthworks was excavated, with about 9 million cubic metres backfilled behind the gravity quay walls.

The slurry cut-off wall works benefited from the food quality supervision and the project was declared by all parties to have been a great success, further confirming Dura Soletanche Bachy’s application of expertise and experience combined with local knowledge, resources, and commitment.

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