E4014 Construction Surveying Pavement Setout

Road Construction Consists of a number of sequential steps –clearing –earthworks –drainage works –pavement construction –road furniture

Road Construction - Clearing When –occurs prior to commencement of earthworks Where –1.5metres outside road formation How –remove all trees and other vegetation

Road Construction - Clearing Surveyor’s Role –mark limits of road formation –batter points + 1.5metres –stakes with flagging or flag trees –use plans and tables

Road Construction - Clearing Existing Survey Control –baseline survey marks and offsets –permanent marks & bench marks Accuracy of Setout –probably ±0.5metre horizontal

Road Construction - Drainage When –before major earthworks keep construction site dry –after major earthworks to keep subgrade dry

Road Construction - Drainage Surface Drains Where –catch drains –catch surface water flow over adjacent natural surface and divert it into the drainage system –2metres from edge of cutting –maybe construct bank rather than cut surface drains When –before major earthworks

Road Construction - Drainage Surface Drains Where –Table Drains collect surface water draining off the road pavement wide and deep enough to collect and hold all surface water deep enough to intercept any subsoil moisture close to the surface discharge onto natural surface or into culverts every 100 metres When –after major earthworks - before subgrade construction

Road Construction - Drainage Surface Drains Where –Levy Drains used on hills to collect run-off from pavement area and direct it into flumes which carry the water down the embankment prevents scouring of the batters in fill When before and after major earthworks

Road Construction - Drainage Surface Drains Where –kerb & Gutter urban form of table drain also used in rural road cuttings normally constructed by an extrusion machine When after major earthworks and pavement construction

Road Construction - Drainage Subsoil Drains Where –constructed to prevent damage by underground water from water seeping down through the pavement water rising in springs water flowing downhill in the upper soil layers –control is achieved by –intercepting ground water before it reaches the roadway –lowering the water table by providing outlets for reservoirs surrounded by impervious barriers –subsoil pipes are usually located – in the shoulder between the pavement and the table drain –under the edge of pavement

Road Construction - Drainage Subsoil Drains Where –Culverts carry water from one side of the road formation to the other pre-cast concrete pipes, pre-cast concrete boxes, insitu concrete boxes, corrugated steel pipes and arches When –after construction of sub-grade, before placing the sub-base

Road Construction - Earthworks Proper construction involves –clearing –stripping of topsoil –drainage of swampy areas –removal of poor materials –compaction of natural surfaces –benching of steep slopes –spreading and compaction of fill materials

Road Construction - Earthworks Preparation of Site –clear all timber –utilities re-location of existing utilities conduits for future utilities will save cost and damage to road formation at a later time

Road Construction - Earthworks Preparation of Site –access through the site for current traffic away from construction site in rugged country locate the side-track in the position of the final catch drain on the up-hill side of cuttings

Road Construction - Earthworks Preparation of Site –Removal of topsoil valuable commodity to be conserved for later landscaping wasted in fills and destroyed by having fills placed over it removal of top soil ensures firmer foundation of fills stockpiled in heaps of less than 1 metre in height –if buried for long periods fertility is lossed

Road Construction - Earthworks Preparation of Site –earthworks operation comprises the following operations formation of cutting by excavating through the high ground formation of embankments by filling over the low ground shaping the ground or finished surface to true formation levels excavation for drainage works

Road Construction - Earthworks Preparation of Site –earthworks operation will involve excavating or loosening natural material loading the material into haulage units transporting the material from cuttings or borrow pits to fill sites dumping the material compacting the material

Road Construction - Earthworks Preparation of Site –Cut & Fills often the largest task in road works often the most costly operation in terms of total sums of money involved speed and efficiency depends largely on the quantity and types of earthmoving plant available –initial plant selection for a site will effect the its overall progress

Road Construction - Earthworks Preparation of Site –Cut & Fills, cont in most materials except rock the factor governing the speed of work is likely to be transporting of the material and not the excavation itself capacity of the haulage system must equal the maximum digging output it follows that the haul should be kept as short as possible

Road Construction - Earthworks Preparation of Site –Cuttings Through Cuts –may be through a small hill or over the top of a large hill to lower the grade of a road –prior to construction the material type must be identified and the angle of repose estimated Side Hill Cuts –part of the road in cut and part in fill –enables balancing of earthworks –embankment portion tends to move downhill, better to be full cut

Road Construction - Earthworks Preparation of Site –Sequence of operations in CUT excavate to reach formation level or to remove alll unsuitable material transport away from site the undesirable soils –organic top soil, heavy highly plastic water-logged clays, loose sand haul suitable material from cuts to fill areas

Road Construction - Earthworks Preparation of Site –Fills eventual aim of all fill work is to position the the subgrade underlying the pavement layers in the right location and at the correct level and to provide drainage to maintain its condition

Road Construction - Earthworks Preparation of Site –Removal of material too weak to support fill highly organic clays, saturated clays in swamps, silt and mud –compact the natural surface of fill sites by rolling

Road Construction - Earthworks Preparation of Site –Fills material should be obtained from as near to the embankment site as possible material should be stable, high bearing strength and a free draining nature sand gravel mix, sand clay mix and sand silt mix are suitable fill materials when correctly placed

Road Construction - Earthworks Preparation of Site –Sequence of operations in FILL drain water from hollows and holes, dispose of sludge before filling is begun spread the fill material into horizontal layers not more than 250mm deep thoroughly compact these layers to maximum density

Road Construction Bases and Sub-Bases After the earthworks and compaction of fills, subgrade is brought up the correct formation and trimmed

Road Construction - Bases and Sub-Bases Road Pavement –sub-base layer, maybe stronger than the underlying subgrade –base course layer stronger than the sub-base –surface course stronger than the base course wheel loads which are most intense near the surface are taken by materials which are able to accept the load without significant deformation

Road Construction - Bases and Sub-Bases Base Course –Rigid cement concrete with or without the addition of a separate wearing course used in roads effected by flooding or subjected to heavy traffic loads

Road Construction - Bases and Sub-Bases Base Course, cont –Flexible bases natural materials which deflect slightly under loads common in Qld are soil aggregate, crushed rock and uncrushed stone level control required as the material is placed in layers deep enough to ensure required compaction can be achieved if tests have not been done on the material the loose layer should be placed 25% thicker than the desired final compacted layer