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River works: bearing pilesRiver and marine works often as not require specialist knowledge particularly regarding checking soil condition andworking on floating plant and unstable ground.In this short work, only the installation of piling is considered.Bearing piles are taken to include piles capable of resisting lateral loads (eg mooring loads) as well as vertical loads.Such piles may be driven as raking piles.Method of installationIt is usual to drive temporary piles from a moored floating platform and then to erect a temporary staging from whichto pitch and drive the permanent piles. During driving, each pile is held in a ‘gate’ (or guide) to achieve the specifiedtolerances for location and rake; of necessity these tolerances are commonly less onerous than for land-based piling.The difficultiesThe major difficulties in setting-out are measuring distances over water and providing stable reference points.A (temporary) reference pile can incorporate a sighting mark but, if so, it is important to check for oscillation of thepile, particularly in fast currents.Check that sight lines to or from water level will be unobstructed whatever the state of the tide or water level.Communication can be difficult and a radio link is advisable.Locating piles by bearing and distanceProbably the most convenient method of locating piles over water is to use a Total Station of GPS system.Locating piles by bearing onlyFor lines of piles roughly parallel to a river bank, an alternative method may be to use bearings only from anappropriate pair of reference points. The disadvantage of this method is that ‘three-way’ communication is required.Locating piles with grid lines and bearingsFor piles in lines roughly perpendicular to a river bank, where practicable: establish reference points defining these grid lines set up reference point some distance along the bank and calculate bearing of each pile from this point for each pile use two theodolites/Total Stations to set out the grid line and the intersecting bearing.Note: If piles are constructed from the river bank, tape along grid line on the temporary staging used for piling.CIRIA C709105