Equipment Most Commonly Used
Where haul distances render dozer operation uneconomical, material is moved either by loading into trucks or by means of scrapers.
A variety of trucks is available for hauling loose materials on earthworks jobs as well as the conventional highway truck, there are off-highway vehicles which have fewer axles than their highway counterpart and whose axle loads exceed the regulation limits.
(a) Highway Trucks with general purpose tipping bodies are suitable for the cartage of materials from outside sources to the site of work, and for the cartage and distribution of material on the site.
They can operate at comparatively high speeds on the site but require a reasonably firm and smooth ground surface. As they bog easily they are unsuitable on soft sites.
Their main application is for very long hauls where haul roads are good and axle load limitations apply (e.g. for hauling selected fill from a pit outside the limits of the works).
(b) Off-Highway Trucks are suitable for hauls of up to 3 km at relatively high speed on good haul roads but at reduced speed when working on soft ground. They are usually the most suitable equipment for hauling shot rock (unless the lead is very short in which case a dozer might be used).
Their axle loads are usually high and, unless they are equipped with abnormally large tyres they may bog on wet sites. Also, one large vehicle may do more damage to a haul road than several small ones.
Their larger body offer a bigger loading target for the loader bucket which may increase production of the loader. The high sided body of some of the larger wagons may however, be unsuitable for some types of loaders. (This possibility should always be investigated when matching loaders and trucks).
Owing to their large capacity they are more economical than smaller machines under conditions where they can develop their speed and where they are not delayed by restrictions at the loading and tipping points, but the breakdown of a large carrying unit causes a greater proportional loss of output than that of a smaller unit.