Download - Engineering Surveyor

Buildings and structures: pilingResponsibilitiesPiling may be sub-contracted to a specialist piling contractor. The piling contractor may then ask the main contractorto do the setting-out or may prefer to use his own engineer. In either case, the final responsibility for correctlysetting-out normally remains with the main contractor’s engineer.Major problems associated with setting-out piles are: soil disturbance from driving displacement piles instruments disturbed by vibrations from piling process spoil from borings may obstruct fields of view piling rigs need space to manoeuvre most piles have to be set out individually the site engineer must constantly be available to assist and resolve difficulties.Setting-out on small/medium sitesWhere the number of piles is modest: set markers at the required positions, using a bricklayer’s line and steel tape, from the corner profiles orsite grid define a suitable baseline and record distances to each marker from at least two stations remove the markers, then relocate each pile position when the piling rig is ready to work.Setting-out on large siteWhen the site is large and the pile positions spread widely, it may be more appropriate to locate pile positions bybearing and distance or by coordinates using a Total Station. Check critical pile positions, eg at the ends of a row ofpiles, by making redundant observations.LevelsFor cast-in-place concrete piles: install temporary level peg adjacent to the completed bore check founding level by using weighted steel tape give ganger dimensions from peg level or top of casing to concreting level (not cut-off level).After installationBefore piling rig is removed from site: check construction tolerances of piles report any discrepancies on the pile log sheet agree remedial action with the supervising authority.Raking pilesWhen setting-out raking piles it may be necessary to allow for the difference between the existing (working) groundlevel and the required level of the pile cap or pile cut-off level. Because of the inclination of the pile, the position atground level will be displaced along the direction of rake by a horizontal distance d tan α, where d is the differencebetween the existing ground level and the specified pile cap or cut-off level and α is the inclination of the pile fromthe vertical.CIRIA C70969