Civil Engineer in South Africa - Volume 30, Issue 1, 1988
Volume 30, Issue 1, 1988
Source: Civil Engineer in South Africa 30 (1988)More Less
The Du Toitskloof Tunnel project was the largest tender ever let by the National Transport Commission when it was awarded in October 1984. it has also made history by being the first major civil engineering contract in South Africa to make use of the selected subcontract format. This paper describes the main principles of selected subcontracting and how it was successfully used for the tunnel project. Comments are also given from both the consulting engineer's and the contractor's points of view on the use of this contract form on Du Toitskloof.
Author D.J. GraySource: Civil Engineer in South Africa 30 (1988)More Less
Long high-density road tunnels are potentially hazardous. Special installations are required to render them safe and to minimize the risk of accidents. This article reviews the electrical and mechanical equipment installed in the Du Toitskloof Tunnel (now renamed the Huguenot Tunnel), the longest road tunnel in Southern Africa.
Source: Civil Engineer in South Africa 30 (1988)More Less
The construction methods employed and the specialized equipment used on the project are described. Details of the design aspects and the construction of the soft ground section to the second tunnel are provided. An alternative technique was used: 'multiple face' excavation supported by vacuum drainage of the ground water table.
Author T.N. CockcroftSource: Civil Engineer in South Africa 30 (1988)More Less
Planning for the present Du Toitskloof project began as long ago as 1970. Owing to the energy crisis in 1973 and subsequent fuel supply problems for South Africa, then, were insufficient funds available to proceed with construction of the project at the earliest opportunity. This paper describes the history of the planning as well as giving details on the various facets that had to be considered during the planning and design phases. The tunnel was completed and opened to traffic on 18 March 1988 by State President P W Botha, who also named it the Huguenot Tunnel.
Author Z. KovacsSource: Civil Engineer in South Africa 30, pp 7 –13 (1988)More Less
The storm was caused by a cut-off low weather system. The maximum rainfall was in the same order as that of tropical cyclone Domoina, but the flood peaks were, on the whole, less extreme. Very 'rare' flood peaks seem to occur rather frequently, consequently there is an urgent need to develop more realistic statistical analysis.
Source: Civil Engineer in South Africa 30, pp 15 –20 (1988)More Less
Extreme storms and the resulting floods over Natal appear to come from two distinct weather-generating mechanisms. The paper describes the estimation of the mixed distribution functions for the two components and attempts to regionalize large storms for design purposes. Conventional extreme value analysis tends to underestimate the arrival rate and therefore the magnitude of the rarer events. In addition, it is found that for large coastal storms, conventional area reduction factors tend to underestimate large-catchment, flood-producing rainfall, especially for long durations.
Source: Civil Engineer in South Africa 30, pp 21 –28 (1988)More Less
The exceptional continuous heavy rain in the catchments of the major Natal rivers flowing through Durban caused very high flood levels to occur. The magnitudes of the floods are considered, as are the means of determination of the flows.
The major damage due to the high flows of the rivers, particularly in respect of the Umgeni and Umlaas Rivers, created major problems in maintaining water supply and waste water treatment services in the entire densely populated metropolitan area. The steps taken to deal with these problems are outlined. Also considered are the effects of property flooding, damage to other services and the resultant change in river regimes.
Author B. WalfordSource: Civil Engineer in South Africa 30, pp 29 –37 (1988)More Less
The September 1987 floods in Natal, which caused extensive damage to property and loss of life in the densely populated areas, also caused extensive damage to the bulk water supply infrastructure supplying the Pietermaritzburg and Durban metropolitan areas. These floods were described by the Minister of National Health and Population Development as 'the worst natural disaster in South African history'.
This paper gives details of the damage to the bulk water supply infrastructure, the mobilizing of resources to attend to the repair of the damaged works, operational problems experienced at the waterworks during and after the crisis period, and lessons learnt from the flood with respect to the bulk water supply. Consequences of the reduction in the quantity of potable water available to consumers are also discussed.
Source: Civil Engineer in South Africa 30, pp 39 –42 (1988)More Less
The excessive rains that fell over much of Natal at the end of September 1987 resulted in damage estimated at R96 million to rural roads and bridges. Damage was caused at more than 400 places and included 28 bridge structures, 130 bridge approaches and 40 causeways. No modern bridge structures were damaged, although some of the approaches were washed away. The damaged structures were mostly between 26 and 42 years old.
Die uitsonderlike reen wat teen die einde van September 1987 oor die grootste deel van Natal uitgesak het, het skade ten bedrae van R96 miljoen aan plattelandse paaie en brûe veroorsaak. Skade het by meer as 400 plekke voorgekom en het 28 brugstrukture, 130 brugaanlope en 40 laagwaterbrue ingesluit. Geen moderne brugstrukture is beskadig nie, ofskoon sommige van die aanlope weggespoel het. Die beskadigde strukture was meesal tussen 26 en 42 jaar oud.
Author P.A. De VilliersSource: Civil Engineer in South Africa 30, pp 145 –147 (1988)More Less
The history of the Du Toitskloof Pass goes back to the early 1800s when routes from Cape Town to the interior were being investigated by the authorities. However, in 1845, the choice of Bains Kloof as the major new route across the mountains resulted in Du Toitskloof going back into obscurity until the early 1930s, when it again came into the limelight. Construction of the existing pass began in 1941 using Italian prisoners of war, but was only completed in 1948. By 1965 the capacity of the pass became inadequate and planning of a new route was undertaken, which resulted in the present tunnel, opened on 18 March 1988 by President P W Botha and now known as the Huguenot Tunnel.
Author S.A. GerberSource: Civil Engineer in South Africa 30, pp 149 –152 (1988)More Less
Die bou van die Hugenote-tonne1 tussen Paarl en Worcester op Nasionale Roete N1 is die grootste enkele projek wat die Nasionale Vervoerkommissie nog aangepak het. 'n Hele aantal kleiner, maar ewe interessante, kontrakte het dle hoofkontrak voorafgegaan om die terrein voor te berei. Dit sluit in die bou van 'n loodstonnel, die toepassing van grondbevriesing in die ontgrawingsproses van die sagte grondgedeelte van die hooftonnel en die bou van die indrukwekkende Hugosrivier-viaduk. In die hoofkontrak is baie suksesvoile gebruik gemaak van 'n stelsel van gekose onderaannemers vir die uitvoering van gespesiaiiseerde werk, waarvan die elektro-meganiese toerusting van die tonnel en sy beheersentrum die belangrikste was. Na suksesvolle onderhandelings met die aannemer is die oorspronklike kontrak uitgebrei om ook die ontgrawingswerk van die toekomstige dubbelbaantonnel intesluit.
The construction of the Huguenot Tunnel between Paarl and Worcester on National Route N1 is the largest single project yet undertaken by the National Transport Commission. A number of smaller, but equally interesting, contracts like the construction of a pilot tunnel, the use of ground freezing methods for excavation in saturated soft material and the building of the imposing Hugo's River Viaduct prepared the scene for the main tunnel contract. In the main contract a system of selected subcontracts was very successfully applied for specialized work, with the electro-mechanical equipping of the tunnel and its control centre being the most important. As a result of successful negotiations with the main contractor, the original agreement was extended to include the excavation of the future double carriageway tunnel.
Source: Civil Engineer in South Africa 30, pp 169 –170 (1988)More Less
The Du Toitskloof Tunnel was first mooted as a solution to a more efficient link between Cape Town and its hinterland in the 1950s. Over time the Du Toitskloof Pass became increasingly inadequate as far as traffic capacity and road safety were concerned. Between 1970 and 1978 various designs were put forward for a tunnel through the pass. Initially the tunnel was planned to be a six-lane, twin-bore structure with dual carriageway approach roads.
In 1974 the National Transport Commission decided to scale down the project and build only one bore since the traffic volumes and growth rate were decreasing as a result of the fuel crisis and did not warrant this additional capacity. In 1978 the cross-section of the proposed tunnel was reduced to two lanes with a consequent saving of R20 million. The spacing between the first bore and a future doubling of the tunnel was also reduced, which enabled savings to be made on the approach fills and bridge structures. However, as the need for the tunnel was evident, construction began on the pilot bore in 1977 and was completed in 1979. Work began on the approach structures in 1980 and in 1981 the soft ground tunnelling was started. Both projects were completed early in 1982. Construction on the main tunnel contract started in 1984.
Source: Civil Engineer in South Africa 30, pp 171 –173 (1988)More Less
With complete triangulation cover, approximately 60 per cent of which is down to tertiary or third order density, South Africa prides itself on being one of the few countries in the world and the only one on the African continent with a fully integrated survey system. Though this national control ensures that cadastral, road, canal, dam basin and other major engineering surveys are performed on a common system, the quality of this network, especially the inherent scale, does not normally satisfy the standard of internal accuracy necessary for extensive intricate construction projects.
Source: Civil Engineer in South Africa 30, pp 175 –178 (1988)More Less
A comprehensive geotechnical investigation including a pilot tunnel was carried out for the Du Toitskloof Tunnel. These investigations highlighted zones where special precautions had to be taken and significantly reduced the risk of unforeseen conditions, thus allowing more realistic tender prices for the various phases of the project.
Source: Civil Engineer in South Africa 30, pp 179 –183 (1988)More Less
Author L.A. RohrigSource: Civil Engineer in South Africa 30, pp 213 –214 (1988)More Less
The operation and maintenance of the Huguenot Tunnel and Tollroad has been contracted out by the Department of Transport to Concor Construction, a member of the Tunnel Joint Venture. From a development phase in which client, consultant and contractor jointly participated, an operations contract was arrived at that is unique in South Africa. A suitable organization had to be planned, created, trained and installed to ensure the continuous operation of this tunnel / tollroad. A brief summary of the organization and features of the contract is given.