Download - Engineering Surveyor

Roads: levelsThe site engineer should begin by establishing TBMs along the route, ensuring to close out the levelling run andprove the accuracy of the TBMs, as described in section Benchmarks, and then proceed as follows.Cross sectionsSet out profiles generally at 20 m intervals or preferably at 10 m intervals.Unless the level information is provided, the site engineer will have to calculate the levels using whatever informationis provided on the site drawings. All calculations should be shown on a Site Information Sheet and filed for reference.Note: It is usually possible to position centre-line and offset pegs to coincide with the level points shown atcross- and longitudinal sections.ProfilesFor each section where profile is required: determine channel levels from drawings or by calculation decide offset of profiles from centre-line calculate required profile levels, taking into account offset distances and adding 1 m for height of traveller(see diagram) set up profiles mark reduced level and chainage on profile provide details of profiles on Site Information Sheets check profiles daily for disturbance by sighting over three or more profiles.Where profiles are required on existing carriageway areas (ie hard areas), or where pegs would cause anobstruction, ‘stand up’ profiles (similar to a traveller) can be used, set up for a particular location. These can beplaced when required, then removed to allow traffic flow afterwards.TravellersA convenient form of traveller is shown in the diagram opposite. The height of the cross-piece can be adjusted fromsay, 1.5 m to 1 m as the construction proceeds.Note: Excavation may be higher than the formation level if a protection layer is required.After earthworks completeAfter earthworks are complete, the need for accuracy in setting-out becomes imperative because of the cost ofmaterials and final riding quality of the road’s surface. Set pins or kerbs to level for sub-base, base and surfaceconstruction. Alternatively, wire lines may be required to guide paving equipment. Check and agree levels with thesurfacing sub-contractor.Suggested colour code for profilesA suggested colour code for profiles (and pegs) is shown in the end-papers.CIRIA C70993