E4014 Construction Surveying

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E4014 Construction Surveying

• Pavement Setout

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Road Construction

• Consists of a number of sequential steps
• clearing
• earthworks
• drainage works
• pavement construction
• road furniture

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Road Construction - Clearing

• When
• occurs prior to commencement of earthworks
• Where
• 1.5metres outside road formation
• How
• remove all trees and other vegetation

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Road Construction - Clearing

• Surveyors Role
• mark limits of road formation
• batter points 1.5metres
• stakes with flagging or flag trees
• use plans and tables

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Road Construction - Clearing

• Existing Survey Control
• baseline survey marks and offsets
• permanent marks bench marks

• Accuracy of Setout
• probably 0.5metre horizontal

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Road Construction - Drainage

• When
• before major earthworks
• keep construction site dry
• after major earthworks
• to keep subgrade dry

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Road Construction - DrainageSurface 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

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Road Construction - DrainageSurface 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

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Road Construction - DrainageSurface 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

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Road Construction - DrainageSurface 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

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Road Construction - DrainageSubsoil 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

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Road Construction - DrainageSubsoil 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

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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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction - EarthworksPreparation 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

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Road Construction Bases and Sub-Bases

• After the earthworks and compaction of fills,
  subgrade is brought up the correct formation and
  trimmed

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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

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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

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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