Appropriate and efficient maintenance of low cost rural roads. Report 3: Investigation of material assessment apparatus.
This element of the project was concerned with the evaluation and development of a pavement and material assessment apparatus in the context of low cost rural feeder roads in developing countries. The aim was to develop a simple method and procedure for the assessment of the quality of those roads. It was proposed that a simple apparatus be adopted which could be made locally at an affordable cost rather than using imported specialist apparatus, thus placing it within the reach and repair capability of poor rural district maintenance authorities.
It was firstly necessary to select an appropriate piece of equipment and then modify it. After initial investigation work, the Dynamic Cone Penetrometer (DCP) was chosen as the equipment to be modified for assessment of roads in-situ and of aggregate materials at source.
It was judged that an ideal assessment procedure for the assessment of low cost rural roads should, as far as practical, comprise a method of assessing strength, stiffness (resilient modulus) and permanent deformation characteristics of the road, in-situ. The same, or similar, procedures should be applicable as a predictive tool, to assess aggregate materials at source (from borrow pits). By this means a simple evaluation technique of the basic
engineering properties of the road construction material in the present works and future construction was planned.
Laboratory and field investigations in the UK allowed the modification of the apparatus to be undertaken. The principle development was the use of the 'flat' tips of various diameters on the DCP apparatus. This was then followed by a number of visits to developing countries to assess the equipment on different soils and establish suitable procedures.
Analysis of the data collected (both from the UK and overseas) yielded some useful and applicable results. It was possible to establish a measure of stiffness by using a modified version of the dynamic cone penetrometer in-situ. Additionally, the version of the equipment developed for testing materials at source yielded some promising results, once an appropriate specimen preparation procedure was developed.
The research demonstrated good applicability of the new techniques in certain
circumstances. On crushed rock materials and in certain lateritic soils it could be implemented directly. However, the evidence for its applicability in a generic manner was not conclusive, suggesting that there may be merit in further research work in the area.
Unfortunately a significant finding was the problem of introducing new ideas and equipment in developing countries due to institutional issues. Such issues are discussed towards the end of the report. To facilitate use of the new equipment and its take-up for the assessment of material in borrow pits, a guideline document has been produced for people wishing to trial the