Road Research

Timaru Herald, Volume CXXXIX, Issue 20077, 6 April 1935, Page 10

Road Research

STUDY IN BRITAIN COMPREHENSIVE PROGRAMME

A comprehensive scheme of road research is visualised by the Road Research Board and described in the board’s first annual report.

One important item is the study of soil physics, which is, of course, concerned with the relation between the subsoil and the road. The ultimate object of the research is to provide the engineer with data which will enable him to design his roads with a surer understanding of all the subsoil conditions which will affect their performance. The stability of roads on made foundations is an obvious example of the great importance of a knowledge of the properties of a disturbed soil. Two distinct lines of investigation are being followed. The first is the laboratory study of those physical properties of the subsoil which, through variations in moisture content, etc., may be so modified as to interfere with its mechanical properties as a foundation to the road. This laboratory study will be supplemented by seasonal field surveys of the actual conditions existing in the subsoil in order to determine the effects of climatic conditions and drainage. The second line of investigation is the collection of information on the influence of subsoil conditions on the performance of roads. Comparisons will be made between roads of similar construction carrying the same traffic load but with differences in subsoil. Attention has been concentrated so far on the laboratory method, and as a first step a soil punch has been devised for extracting soil cores for test. A standard classification has been adopted for the characterisation of the subsoil examples.

Work on aggregates, fillers, and mixtures for use in roads comprises the examination of grading and shape characteristics of aggregates used with hydaulic and bituminous binders; the investigation of the particle size and shape of fillers; and tests on the physical and mechanical properties of mixtures of aggregates and binders. It has been necessary to develop special testing apparatus. Particular points of interest are the examination of sea-

sonal and allied effects of bitumens and bituminous mixtures and the adhesion and wetting properties of bituminous binders to aggregates. Bituminous Roads With regard to bituminous roads, surfaces, and foundations, consideration has been given to the processes involved in bituminous road construction, and a general survey has been made of the literature on the subject. Some initial work has been carried out with a view of developing a suitable method for the analysis of tarred stone used for tar macadam. An examination has been made of samples taken from bituminous roads of known characteristics.

Research work on the forces applied to roads by vehicles has been carried out for the Ministry of Transport by the National Physical Laboratory since 1926. A special trailer and recording outfit was designed and constructed for the measurement of impact forces. This series Of tests is being continued, but the investigation has so far been confined to roads of concrete construction, plain, or surfaced with an asphalt carpet. Further tests are to be carried out under a variety of subsoil conditions.

For the record of the impact imparted to roads special apparatus has been designed and constructed at the National Physical Laboratory. The first measurements are being made on a sixwheeler chassis of about 6 tons normal capacity, the instruments being fitted to the rearmost axle.

At the request of the Ministry of Transport a special form of motor bicycle and side-car was developed some years ago at the National Physical Laboratory for comparing the behaviour as regards side-slipping of rubber-tired wheels on different road surfaces and under various types of weather conditions. A special mechanism has now been designed for combining observations and recording the skidding coefficient directly on a chart. Other methods for measuring skidding or side-slipping on road surfaces are under consideration. 4