F104TEC Substructure

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used to determine conditions on a construction site.

how these conditions affect construction design and performance

A site investigation must always be carried out

  • the variable nature of the natural components of a site require the investigation to have some flexability built into it.

three elements:

  • Desk study (will indicate the extent of the ground investigation)
    • geological and topographical maps; i.e if a ground is underlain with clay and covered in vegetation with a degree of slope, removal of a significant amount of vegetation will change the groundwater conditions and could lead to heave and land slip.
    • will identify potential problems including cavities, types of problematic soils, mineral extraction, solution features e.g swallow holes
  • site reconnaissance (walk over with a keen pair of eyes and a camera) including site itself, surrounding area and building stock.
    • basic dimesions and maybe a simple soil test
    • position and types of vegetation that may indicate changes in ground conditions, presence of water (localised)
    • potential traffic problems which include heavy plant at the outset of construction
    • indicative streetnames
  • ground investigation
    • ranging from trial pits to more sophisticated types of exploratory techniques
    • typically the depth will be 1.5x width + anticipated depth
    • soil types from Dense gravel through free draining gravel and sand to the more cohesive types of soil which include clay and silt which retain water and cause problems

Objectives requiring a site investigation

  • how a the development may be economically constructed, foundation being a significant factor
  • feasability of alternative METHODS of construction
  • in terms of extending an existing structure
  • if remedial work is required i.e. slope instability

primary objectives of a site investigation

  • suitability i.e. access
  • geotechnical parameters; safe, adequate and economical design, consider aspects of previous use i.e soil improvements
  • Information to acheive best method of construction; may apply to the entire site of sections. i.e. control of ground water (dewatering system) suitability of on-site geo technical material
  • Impact (on surrounding area) i.e. the effect that a dewatering system may have.


can either br permanant sheet (close) piling, secant ( or application of pencol, has  advantages over traditional piling Compresses soil giving it load bearing capacity)

or temporary by using a wellpoint system.

  • to improve the structural capacity of the soil
  • to enable safe working conditions below the ground

encompasses - changing the water content of the soil-

although 3 types of water are present on any site only surface water and ground water pose problems

intercepting drains deal nicely with any surface water (french drains)

small amounts of ground water can be dealt with by a sump and pump system as long as the water can be pumped…


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