AUTHORS' PRESENTATIONThe Authors said that the airport was sited in the only possible place within 15 miles of Kuala Lumpur which had obstruction-free approaches.The threshold levels adopted allowed for an approach plane of 1 in 100 for the first 1000 ft from the threshold and 1 in 66 thereafter. The threshold levels themselves were determined by the level of the road to Sungei Buloh village in the north and the low-lying hills of the rubber plantations in the south. To economize in earthworks the runway was constructed having a falling gradient from the south of 1 in 200 and a rising gradient to the north, from approximately mid-way along the runway, of 1 in 600.88. The drainage system for the airport was designed to accommodate a rainfall density of 6 in./h during a 20 min storm. As the Airport complex was located in the watershed of the Sungei Damansara the storm water had to be collected on the western sicle of the airport and channelled beneath the flight strip to be discharged into the Sungei Damansara. Since the water from the Sungei Damansara was being used as a source of supply to Kuala Lumpur it was necessary to install kerosene interceptors to the two main parking aprons.89. From the borehole samples and initial earthwork cuttings it was thought that the soils could be reasonably identified by their colour and vertical distribution which were described in the Paper. Laboratory and field tests were also carried out on the soils to establish their strength characteristics, uses as construction materials, and the amount of lime necessary for their stabilization. When evaluating the strength of the finished pavements by the plate-bearing method it was observed that the relation between the deflexion of the plate and the log of the number of repetitions was not linear. The normal method of obtaining the 1.c.n. at 10 000 repetitions could not be applied and it was decided to interpret the results by the method used by F. R. Martin.' 90. One of the main reasons for the quite reasonable price obtained for the airport pavement was the use of locally available cheap materials. Preliminary tests were carried out on these materials and the results of the tests were given to the tenderers who were asked to satisfy themselves, by additional testing, of the suitability of the materials for the type of pavement specified. The tenderers in effect had to design the bitumen-bound base before tendering and submit t h e i designs with their tenders. The epoxy resin bitumen surface dressing was applied to render the apron fuel proof. 91.They wished to make the following corrections to the Paper. In 5 13 the reference should be to soils of Types 2 and 3, not 1 and 2. In Fig. 5 93.The pavement was not only well designed for its structural adequacy with reasonable economy, but also in its use of construction methods well adapted to the wet climate. MrSkepper had stated that they had no difficulty in consistently compacting soil to a relative density of 95% modified AASHO. Those who worked in Britain would perhaps be more ...
The need for major maintenance or reconstruction of a pavement is described in 5 4 in engineering and operational terms. In addition a runway, or other Operational pavement, may become unsatisfactory because it is below strength for aircraft which are operating or about to operate. If strengthening is delayed, the maintenance problem can increase quite rapidly. Further delay will cause a pavement to deteriorate to a point where economical strengthening is impossible. It is, therefore, important that the Engineer should decide, as early as possible, on any major strengthening measures.48. Fortunately a rigid (concrete surfaced) pavement, regularly inspected, will give early warning of trouble in the form of corner and edge cracks of greater than casual occurrence. It is less fortunate, however, that arrangements for large-scale surfacing take some time, whether it be the preparation of a contract, stockpiling of materials or purely financial difficulties. In the event of severe overloading the interim deterioration may be quite rapid.49. Asphalt surfacing of 100 mm or more on an undamaged rigid pavement, that is one with few loading cracks or areas weakened by fatigue, strengthens the structure considerably. The superimposed layer spreads the load, producing less pressure on the pavement, and, more important, moving the centroids of critical wheel loads further from edges and corners of slabs. In addition, in the UK, the daily variations in temperature at the top of the concrete slab will be almost negligible, so that temperature stresses are greatly reduced and the slabs wiIl probably exhibit no measurable warping either as upward curling in late summer and early autumn or arching earlier in the year. The same applies, with seasonal variations. in most parts of the world.50. Whether a rigid pavement has been resurfaced with asphalt to reduce maintenance, to improve operational performance or for strengthening, there is a problem in evaluation of the strength of the resulting composite construction. If the concrete construction is in good condition and a reasonably cautious evaluation is made of the concrete strength, the problem is fairly easy to solve, for surfacing thicknesses of 100 mm to 150 mm, provided the surface is unbroken or exhibits no more than hairline reflective cracks. Thicker layers of asphalt and underlying layers which are more or less damaged, as well as open reflective cracks (e.g. above expansion joints), make the problem much more difficult. Surface load tests, short of loading nearly to destruction over large areas, will lead to no reliable conclusion. These diffculties have been recognized by some authorities on pavements, who have from time to time given somewhat arbitrary evaluations of the various materials in multi-layer pavements for comparison with their own conceptions of the design and evaluation of flexible construction. Eventually, however, the evaluation will depend on the judgement of the Engineer who will need,
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