The history of the problem of cracking of buildings on heaving soils is briefly descriptionbed with reference to observations made on buildings, methods used to prevent or minimize damage, identification of soils which are dangerous and prediction of the amount of movement that can be expected to take place. The possible effect of climate on soil behaviour is considered and the direction in which future research will probably take place is indicated.
Some observations are made on the behaviour of buildings founded on collapsing soils and on the progress made in the identification and prediction of collapse. Future research projects are suggested which, if successful, may result in an economical solution to the problem
Met die ontwerp van plaveisel moet ten minste drie vereistes nagekom word :- 1. Die elastiese defleksie moet binne perke gehou word. 2. Die plastiese vervorming moet binne perke gehou word. 3. Die skuifweerstand van die sisteem moet genoegsaam wees om algemene faling te verhoed. In hierdie artikel word bogenoemde aangeleenthede kortliks behandel.
Photogrammetric methods have become a recognised procedure for the compilation of plans and maps for many engineering projects. Such maps can be prepared under appropriate specification to any practical accuracy in planimetry as well as in height from aerial photographs.
The development of high quality roads has contributed greatly to the country's progress but many problems still require research effort. Comments are made on gravel roads, the design of bituminous roads, use of decomposed rocks, soil stabilization and special problems in South Africa.
The paper illustrates the development of public health engineering during recent years. Present methods and future trends are discussed in respect of the various phases of this branch of engineering. These include water supply and purification, the conveyance and treatment of sewage, refuse removal and disposal, and the control of air pollution. Mention is also made of now health hazards with which the profession will have to contend in future.
Die uitbreiding van stede en dorpe wat volg op die ontwikkeling van nywerhede skep ingewikkelde probleme i.v.m. die voorsiening van water en die besoedeling van waterbronne. In baie gevalle word die probleem nog verder gekompliseerd as gevolg van vooroordeel wat berus op gebrekkige kennis.
The paper deals primarily with design capacities for both conventional and high rate sludge digestion under South African conditions. Consideration is also given to two stage digestion sterilization of the digested sludge and the potentialities of garbage grinders.
The reasons why screenings and detritus are removed from sewage as a preliminary step in purification are sketched briefly, and it is suggested that the object of these processes will be modified in future to minimise the disposal of the material removed from the sewage. The mechanism of the settling of screened sewage, humus and activated sludge is discussed and the need for a settling characteristics analysis as an essential step in the design process is put forward. A practical method of determining the settling characteristic is descriptionbed. The hydraulic considerations in sedimentation tank design are discussed briefly and the adaptation of the design of the tank of the future to function in harmony with the natural process of sedimentation is suggested.
The paper outlines the causes and character of air pollution in the larger cities, and suggests measures to minimise them. Various methods of dealing with the products of incomplete combustion are discussed and the immediate need for constructive methods to tackle these problems are emphasised.