The design of multi-anchored tieback soldier pile walls in Sandton is typically based on either empirical methods or two-dimensional finite element modelling, ignoring the effects of matric suction in unsaturated residual granites. The designer, however, often relies on previous experience in a similar subsurface profile rather than established theory, to assess the ability of the soil to arch between soldier piles.

This paper discusses key observations and lessons learnt from the geotechnical investigation, design and construction for the four level Mt Edgecombe Interchange. The interchange is the largest and most complex yet to be constructed in South Africa and is situated on a weak succession of coastal sands and clays to depths of over 60m. A significant feature of the project was the geotechnical works.

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.

Mechanically Stabilised Earth (MSE) walls have a growing application in place of conventional retaining systems for varying reasons, most notably economy and constructability. However, there have recently been a number of failures or instances of poor performance of these systems throughout the southern African region. An evaluation of these indicates that there are two fundamental causes for poor performance.

Technical paper discusses the geotechnical investigation and design of various aspects relating to some of the geotechnical constraints encountered for the upgrade and widening of the N2 freeway between Mt Edgecombe and the Tongaat Toll Plaza including: Settlement and consolidation of approach fills to the uMdloti Dual Viaducts, Pile foundations to Umhlanga River Bridges and uMdloti Viaducts and Lateral support to various cuttings and structures.

Article discusses the increased use and applicability of the Continuous Surface Wave Test by example from three recently completed projects; a major bridge over the Jukskei River, a 4 storey library at Stellenbosch University, and the rehabilitation of a dolomite subsidence on the R21 Freeway. The examples show how the test is useful in supplementing information on ground conditions, in deriving design parameters where no other test method is possible, and as a tool used for quality assurance purposes on a major construction project.

Technical paper discusses the design and design verification of Screwed-in-Casing Augered Piles (SICAP) for the Mt Edgecombe Interchange at Umhlanga, Durban. In oder to optimism the pile foundation design and verify design assumptions, full-scale pile load tests were undertaken on three test piles using the Osterberg load cell (O-cell). In addition to confirming the ultimate design parameters the results of the load test provided valuable insight to the load settlement performance exhibited by these piles and enabled the design to be adjusted accordingly.