It has been accepted in international leadership circles that the South African Constitution is arguably the best in the world. The recent ruling of the highest court in the land on the Zuma-Nkandla saga is evidence that our democracy works. Parliament has made a mockery of it, but this country - with its people, its natural heritage, its future - is worth fighting for.
Geotechnical work often demands creative solutions to complex challenges. That's the nature of the game, and there are few better at it than Franki Africa, who has developed a reputation throughout Africa for their innovative and cost-effective solutions in a host of vastly divergent geological conditions. One such example is the Transnet National Ports Authority's Port Elizabeth Jetties Contract.
Dr Hendrik Kirsten, the 2015 recipient of the SAICE Geotechnical Gold Medal, has always contended that, "If you like what you do, then there's no end to you." This, and his total commitment to the pursuit of his goals, reflect how the formidable body of work he has been involved in for over 40 years - epitomising the scope and diversity that geotechnical engineering is involved in and its fertile cross-pollination of ideas - has been possible.
In 2013, Transnet National Ports Authority (TNPA) commenced with upgrading of the existing fire-fighting system of the oil tanker terminals in the Port of Cape Town (Figure 1). This included the construction of a new pump station, which would house booster pumps on the ground floor and a 250 kilolitre water reservoir directly above the pump station on the first floor. The design bearing pressure exerted on the ground by this new structure would be 150 kPa.
The pump station site is located inside the Port of Cape Town. The fill material (the placing of which started in 1965) comprised hydraulically backfilled material derived from dredging activities, and highly variable end-tipped imported material.
The objective therefore was to design a stable and effective foundation capable of handling loads from a dynamic structure (the pump station) on a highly variable, weak soil deposit.
The performance of clay liners can, even after appropriate design and construction, be compromised by differential settlement of the underlying material, should this occur. CCLs are unable to withstand tensile strains and maintain their integrity. Even at low deformation levels tensile strains are induced in the clay, which may cause cracking (Ajaz & Parry 1975). The hydraulic conductivity and strength of the clays may thus be affected by these phenomena and may create possible flow paths in the clay for contaminants such as leachates.
Geosynthetic materials have been successfully installed as effective barriers in various types of earth and concrete structures over the past 50 years. However, as technology and research in the geosynthetics field evolved, it was found that composite liners have certain limitations, and that heat can significantly decrease the service life of geosynthetic components.
According to the highly respected US Environmental Protection Agency, current standards do not adequately address toxic pollutant discharge, frequently resulting in toxic chemical seepage from unlined ponds and dry waste landfills into ground and surface waters. Although the Agency's concerns refer mainly to pollution caused by coal-related products, the reality is that clean water is the source of life, and hence it is critical to a sustainable future.
Before the launch of the new South African Pavement Design Method (at the time of writing), extensive research was undertaken to evaluate current road pavement material performance (design versus long-term actual performance) in the development of new materials. However, very little interest was shown in a technology which has been proven to benefit pavements by an unequalled value of up to 10 times normal traffic load, thereby allowing a reduction in layer thickness of up to 50%. This means a Category C (ES-0.01 to 0.1) road becomes a Category B road. Applying this technology greatly reduces the cost of construction where a G1 or a cement-stabilised material would have been used.
This technology, which is known as geosynthetics, has a record of more than 30 years of proven results and efficiency in practice. Some new materials currently used in roadworks do not have proven records over such a time span. Although currently classified as materials or products, it is increasingly believed that geosynthetics in fact represent a new technology. Geosynthetics technology is the result of thorough research, field tests and calibration towards the development of a strongly-based formulation for designing.
Geosynthetics technology was recently successfully used in a road rehabilitation project currently under construction near Glentana in the Southern Cape.
The Franschhoek Pass (R45) is one of South Africa's iconic mountain passes, serving as a gateway to the Overberg. The year 2013 saw numerous cases of slope instability along the route due to unseasonably high rainfall. In response, SMEC South Africa (Pty) Ltd was tasked by the Western Cape Department of Transport and Public Works with repairing damaged drainage infrastructure and road surfacing, implementing erosion-mitigation measures and stabilising a progressive, deep-seated slope failure on the lower western flank of the pass. The solution involved the use of an unconventional slope stabilisation method synchronous with the surrounding environment (Figure 1).
Over the past six years Mauritius embarked on major road and traffic infrastructure upgrade projects as part of solutions to improve road user safety, alleviate traffic congestion, boost the industry and facilitate economic growth, with added social and environmental benefits. Positive population growth and an increasing number of road users required construction of dual-carriageway roads capable of accommodating high volumes of traffic. Massive capital investments and acquisition of land were required for these projects, ultimately leading to the planning and alignment of these roads over very challenging topographical, hydrological and geological terrain and environments. The Ring Road Phase 1 project was constructed during 2010-2013, and comprises a 4.9 km dual-carriageway, and one large bridge over the St Louis River, with access roads to industrial and retail areas and the National Convention Centre. Terrain elevation and road alignment required the construction of several large cuts and fills. Space restrictions justified the implementation of large mechanically stabilised earth walls (MSEWs) in lieu of traditional fills.
In early 2014, cracks appeared on the northbound carriageway, followed by the collapse of a 15 m high MSEW portion of the fill (Photos 1 and 2). Observations pointed to a textbook slope failure with "slip at the lip" and "bulge at the toe", indicating that deep-seated movement had occurred. This article summarises the geotechnical investigation conducted to identify the failure mechanisms, the design of remedial measures, and the knowledge and understanding gained for use in future projects.
The first phase of the upgrade of the N2 Freeway Section 26 has seen extensive geotechnical works. A feature of this phase of the project included the widening of the dual uMdloti River viaducts. The viaducts are founded on 45 m deep piles that required subcontractor Keller-Franki to import a massive Bauer BG28 rig for the project. The project also included over 2 km of fabric-reinforced mechanically stabilised earth walls and 2 km of cut retaining walls. This article discusses some of the more interesting facets of the geotechnical components of the project.
The M1 cable-stayed bridge, currently under construction near the Marlboro Drive off-ramp in Sandton, forms part of the Rea Vaya Bus Rapid Transport (BRT) network, one of the largest projects ever undertaken by the City of Johannesburg. The bridge, which is built in partnership with the Johannesburg Development Agency (JDA), will provide vehicular and pedestrian access from Sandton, across the M1, towards Alexandra. Michael Pavlakis & Associates were appointed to carry out the geotechnical investigation and the design of the pile foundations for the bridge.
In the last two decades, the global development model has shifted to idealise sustainable development, as well as to promote 'green' and renewable ideals. South Africa, following the example of other more developed nations, has tackled these ideals by beginning to supplement its energy production infrastructure with more sustainable alternatives and, with the exception of its planned new nuclear scheme, has committed to a reduction in non-renewable production methods over time. This was highlighted in the country's 2012 Integrated Energy Plan, where the National Energy Regulator committed to investing 1 600 MW a year in renewable energy infrastructure, of which half is dedicated to wind energy and the creation of wind farms. With this increase in scope, understanding the complexities of turbine engineering has never been more important for South African engineers.
Foundation designs for these structures pose a series of complex challenges, due to the unique loading characteristics that turbines inherently possess, as well as the wide variety of soil conditions that exist within the South African wind energy corridors. One of these challenges is to provide a safe approximation of the bearing capacity, which must account for the extremely large gravity and moment loads that the structure experiences during normal operating conditions. This leads to very large eccentricities, which can often destabilise a footing to the point of failure. This article introduces and discusses the various turbine loads and how they can be theoretically accounted for in the design of a conventional gravity footing for a wind turbine structure.
The following definition of geotechnical engineering is suggested by a popular search engine: "Geotechnical engineering is a civil engineering discipline that is concerned with building on, in, or with soil and rock. Geotechnical engineers design dams, embankments, cuts, foundations, retaining walls, anchors, tunnels, and all other structures directly interacting with the subsoil, both onshore and off shore." I assume that this definition would generally be accepted by most geotechnical engineers as an adequate definition of geotechnics. However, as Victor de Mello pointed out, we are first human beings, then civil engineers, and then specialists. Therefore we need to be aware of the society we serve. This article sets out to answer this question by reviewing various news articles dealing with issues of geotechnics.
Published results of investigations of variance in geotechnics are understandably scarce. The first study on soil variability was undertaken by Lump (1966), and only in the late 1990s was there renewed investigation. A seminal study was undertaken by Phoon and Kulhawy (1999), which investigated the variances of each parameter in terms of the coefficient of variance (CoV) for various techniques, such as triaxial testing, cone penetration testing (CPT) and standard penetration testing (SPT).
The year 2016 is already well under way, and shaping to be a very active one for the Geotechnical Division. Aside from the traditional Jennings Lecture and a short-course on piling, both presented by Dr Mark Randolph in March, we are also looking forward to the 1st Southern African Geotechnical Conference in May, and several fascinating evening lectures that have been confirmed for the latter half of the year - these include presentations on dolomite by Dr Fritz Wagener, lateral support by Ken Schwartz, and a comparison of compaction techniques by Alan Parrock.
Dr AAB (Tony) Williams passed away peacefully at home in Johannesburg on 4 February 2016, just short of his 90th birthday, leaving his wife Veronica (whom he married in 1953), four children and six grandchildren.