Civil Engineer in South Africa - Volume 22, Issue 9, 1980
Volume 22, Issue 9, 1980
Source: Civil Engineer in South Africa 22, pp 233 –238 (1980)More Less
As a trial in the late 1960's, the design standards for certain lightly-trafficked roads in the south-western Transvaal were lowered in order to reduce the costs and hence increase the length of roads which could be surfaced. One- and two-layer pavement designs were adopted.
Based on the experience with these roads and a thorough structural evaluation of the performance after nine to twelve years' use, the low standard specification is shown to be a viable and economic alternative to the normal provincial standard for a rural road. On the present worth of total costs it is shown to be 26 per cent cheaper than a similar pavement built to the normal standard.
Recommendations are made for the design of pavements for low standard roads in farming areas having a relatively low rainfall.
As 'n proefneming in die laat sestigerjare is die ontwerpstandaarde van sekere paaie met ligte verkeer in suidwes-Transvaal verlaag om die tempo van betering te verhoog en om kostes te verminder. Een- en tweelaag plaveiselontwerpe is gebruik.
Gebaseer op die ondervinding met hierdie paaie en 'n deeglike strukturele evaluering van die paaie na nege tot twaalf jaar se gebruik, word daar aangedui dat die lae standaard spesifikasie 'n lewensvatbare en ekonomiese alternatief is vir die normale provinsiale standaard vir 'n plattelandse pad. Op die basis van die huidige waarde van die totale koste word daar getoon dat die lae-standaard pad 26 persent minder kos as 'n soortgelyke pad wat volgens die normale standaard gebou is.
Aanbevelings word gemaak vir die plaveiselontwerp van lae-standaard paaie in boerdery-gebiede met 'n betreklike lae reënval.
Author P.W. KeeneSource: Civil Engineer in South Africa 22, pp 239 –242 (1980)More Less
Expressions are derived for the stresses developed in steel and concrete when a thin concrete wall suffers a fall in temperature. It is shown that the concrete is unlikely to crack unless there is some external restraint. When restraint is complete and a crack occurs there is a considerable reduction in the tension in the wall. Since it ignores this reduction, the simple formula in Appendix B of BS 5337 for the minimum proportion of steel is invalid.
Source: Civil Engineer in South Africa 22, pp 243 –249 (1980)More Less
This paper describes the design and construction of what is believed to be the first raw water storage reservoir to be built in the Republic of South Africa using hydraulic asphaltic concrete for its waterproof lining. The reservoir is situated in the Eastern Transvaal and provides water storage for the Electricity Supply Commission's Matla power station. The oval reservoir has external plan dimensions of approximately 390 m by 530 m, an 8 m water depth and comprises two equal compartments having a total capacity of 885 000 m3.
The entire internal slopes and floors, having a total area of 140000 m2, are lined with hydraulic asphaltic concrete to provide waterproofing. The various components of the lining comprise a 75 mm base course, overlain successively by a 50 mm bituminous bound drainage layer, two 40 mm layers of hydraulic asphaltic concrete and finally a 2 mm seal coat.
The lining selection is discussed and details of the lining components are given with special reference to laboratory testing and construction procedure.