BGS Civils: foundation conditions

BGS Civils: foundation conditions sample.
BGS Civils: foundation conditions coverage.
Scale 1:50 000
Coverage Great Britain
Format GIS line and polygon data. (ESRI, MapInfo, others available by request.)
Price

Product 1: BGS Civils bundle (all 8 layers)

£0.50 per km2

Product 2: BGS Civils individual layers

£0.30 per km2

Product 3: BGS Civils web viewer (subscription service)

£500 per layer for the first layer. £100 for each additional layers.

Or, £1000 for all 8 layers.

BGS Civils comprises 8 layers: bulking volume, corrosivity (ferrous), discontinuities, engineered fill, excavatability, strength, sulfate/sulfide, foundation conditions.

All products are subject to number of users, licence fee and data preparation fee.

Downloads

This theme provides information on the suitability of a geological material for foundations as part of a suite of GIS layers for different engineering parameters.

The spatial model covers England, Scotland and Wales at 1:50 000 scale and is based upon the soil parent material model, the national geotechnical property database and BGS Geology 50k dataset. It characterises bedrock and superficial deposits in terms of their engineering properties related to the suitability for foundations.

The foundation conditions of rocks and soils are an important consideration for determining how surface construction loads are transmitted into the ground safely and for the lifespan of the project.

What are foundation conditions?

Preparation of ground prior to building foundation.

The foundation is the interface of some form of construction and the ground. Design of the foundations takes into consideration a number of factors including the response of the ground to the stresses produced by the construction. The behaviour, or 'condition', of the ground may be assessed by in situ and/or laboratory tests during a typical site investigation. This dataset highlights common factors to consider when planning for a site investigation or land-suitability assessment.

The main considerations are:

  • strength or bearing capacity
  • settlement (compressibility) and differential settlement
  • volume change of the ground due to climatic conditions
  • subsidence due to natural voids beneath the foundation, leading to ground failure

Other considerations include:

  • weathering and alteration
  • aggressive ground conditions of soluble sulphate, sulphide, low pH or high chloride content
  • foundation excavations protection

Classification

The primary classifiers give a qualitative assessment of the likely ground conditions for foundations. This is based on characteristics including bearing capacity (strength), compressibility, rate of consolidation and the variability of the ground conditions for each unit. A special case for construction above mapped coal seams is also given, and this is also relevant for units that contain coal seams. In these cases this is one of the subsets.

Condition

Additional hazard considerations

Generally good foundation conditions

  • probable volume change (shrink/swell) hazard
  • sulfate/sulfide might be present
  • sand or silt might be frost susceptible
  • possible variable ground conditions (clay and mudstone)
  • low potential for collapse when loaded and saturated
  • possible variable ground conditions due to lithological variability
  • boulders at/just below foundation level might result in differential settlement
  • possible variable ground conditions near surface due to weathering
  • possible variable foundation conditions at interface between granite and altered granite
  • fine-grained head deposits, if present, might contain shear surfaces affecting stability in pits and trenches
  • possible variable ground conditions due to sand/sandstone lithological variability: excavations might be unstable

Generally good foundation conditions but might be locally moderate or poor

  • possible dissolution of gypsum at or near foundation level: collapse breccia and differential settlement might occur
  • sulfate might be present
  • voids or infilled voids in limestone might result in differential settlement

Generally good foundation conditions but may be locally variable or poor

  • voids or infilled voids in limestone might result in differential settlement
  • weathered chalk (silt) might be frost susceptible

Generally good foundation conditions but might be locally poor

  • coal present at foundation level requires remedial measures
    • assess emissions of dangerous gases
    • might be mined out and backfilled
  • possible highly compressible ground and variable bearing capacity; possible differential settlement
  • sand and silt might be frost susceptible
  • excavations might be unstable

Good to poor foundation conditions

  • possible variable compressibility
  • local low bearing capacity and differential settlement
  • flooding of alluvium should be considered
  • might contain shear surfaces
  • excavation might be unstable
  • dissolution of gypsum at or near foundation level: collapse breccia and differential settlement might occur
  • sulfate might be present

Good to very poor foundation conditions

  • possible highly variable ground conditions
  • might contain chemical and physical hazards

Generally unsuitable for most foundation types

  • water
    • changes in water levels possible
    • poor foundation conditions beneath water
  • likely highly compressible ground
  • possible large and differential settlement and aggressive acidic conditions
  • excavations might to be unstable

Generally very poor foundation conditions or poor to moderate conditions (where ground is no longer tidal)

  • highly compressible ground; possible differential settlement
  • salt and sulfide might be present
  • excavation might be unstable

Variable foundation conditions from poor (in dynamic environment) to good (in stable environment)

  • possible dynamic environment: deposition and erosion might occur
  • silt and some sand might be frost susceptible
  • shells, if present, might crush under load
  • excavations might be unstable

Generally unsuitable foundation conditions (unless assessed as stable or stabilised by engineering works)

  • possible unstable ground (assess for stability)
  • excavations likely to be unstable

Difficult foundation conditions (due to the presence of boulders)

  • boulders where present can obstruct foundations
  • potential for differential settlement

Foundation conditions unknown because lithologies are unknown

  • hazards not known

 

Contact

Contact Digital Data for more information.

Hutton field: well correlation diagram.