E4014 Construction Surveying

							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, cont
  – 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, cont
  – 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, cont
  – 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, cont
  – Cuttings and 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, cont
  – 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, cont
  – 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, cont
  – 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, cont
  – 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, cont
  – 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, cont
  – 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, cont
  – 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, cont
  – 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 tp the correct
  formation and trimmed

• Road Pavement
  – sub-base layer, maybe
  – base course layer
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
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