OR/14/030 Introduction

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Entwisle, D C, White, J C, Busby, J P, Lawley R S and Cooke, I L. 2014. Electrical Resistivity Model of Great Britain: User Guide. British geological Survey. (OR/14/030).

These articlesprovides information for users of the near surface electrical resistivity model of Great Britain. This model has been developed as part of the DiGMapPlus program at BGS.

The resistivity of geological units is an important factor in engineering activities where the electrical characteristics of the ground are required, e.g. in earthing of electrical systems. The resistivity of the ground is dependent on a number of factors which include the porewater resistivity, the saturation and the geology.

Background

The near surface ‘electrical resistivity model of Great Britain’ has been developed from previous regional resistivity models carried out to inform the design of earthing systems for Western Power Distribution and United Kingdom Power Networks. This work is reported in Busby et al. (2012[1] and 2014[2]).

The resistivity model is derived using an effective medium methodology to calculate bulk resistivity (Berg, 2007[3]). The BGS National Geotechnical Properties Database (Self, 2012[4]) and information from the BGS Streams database (British Geological Survey, 2009[5]) were utilised to parameterise the input variables in the resistivity calculation. The derived resistivity values were coupled to the geology of Great Britain described in the soil-parent material map (PMM) (Lawley, 2008[6]) using a spatial GIS join. The soil-parent material map (PMM) of Great Britain (Lawley, 2008[6]) describes the characteristics of the near surface zone from which soils develop. Typically, this material is the first geological unit encountered beneath the base of pedological soil. The PMM is derived from the BGS 1:50k scale geological map of Great Britain, known as DiGMapGB-50 (British Geological Survey, 2011[7]). The PMM compilation combines data from the bedrock and superficial (drift) geological maps to produce a model of the surface geology.

References

  1. BUSBY, J P, ENTWISLE, D, HOBBS, P, JACKSON, P, JOHNSON, N, LAWLEY, R, LINLEY, K, MAYR, T, PALMER, R, RAINES, M, REEVES, H, TUCKER, S and ZAWADZKA, J. 2012, A GIS for the planning of electrical earthing, Quarterly Journal of Engineering Geology and Hydrogeology, 45, 379–390
  2. BUSBY, J, LAWLEY, R, WHITE, J, JAMES, I, ENTWISLE, D, BARKWITH, A, HANNAM, J, PACHOCKA, M, MANSOUR, M, MAYR, T and DACCACHE, A. 2014, User Guide DiGMapPlus+ Engineering Properties: Resistivity dataset (version 1). British Geological Survey and National Soils Research Institute. British Geological Survey, Keyworth, Nottingham, UK.
  3. BERG, C. 2007. An effective medium algorithm for calculating water saturations at any salinity or frequency. Geophysics 72, E59–E67.
  4. SELF, S, ENTWISLE, D C and NORTHMORE, K. 2012. The structure and operation of the BGS National Geotechnical Properties Database. Version 2. Nottingham, UK, British Geological Survey, 68pp. (IR/12/056). http://nora.nerc.ac.uk/20815/
  5. British Geological Survey. 2009. Conductivity in stream waters: Great Britain. G-Base Geochemical Map. British Geological Survey, Keyworth, Nottingham, UK.
  6. 6.0 6.1 LAWLEY, R. 2008, The soil-parent material database: a user guide, British Geological Survey Open report, OR/08/034.
  7. British Geological Survey. 2011. Digital Geological Map of Great Britain 1:50 000 scale (DiGMapGB-50) data [CD-Rom]. Version 6.20. Keyworth, Nottingham: British Geological Survey.