Application of electrical and thermal borehole logging to structural and hydrogeological investigations of crystalline bedrock

Ari Poikonen

Research output: Book/ReportReport


In the study electrical and thermal borehole-geophysical techniques are applied to bedrock investigations connected with geological disposal of nuclear waste. The results are also applicable to other engineering purposes where structural and hydrogeological information of bedrock is needed. The study is based on the geophysical measurements carried out at the Loviisa and Olkiluoto nuclear power plant sites. The measurements are part of the site investigation the purpose of which is to assess the suitability of the bedrock for final disposal of low-level and intermediate-level reactor wastes. The specific objectives of the geophysical investigations are to map and characterise fractures and to examine the hydrogeological conditions beneath the sites. Results from the study show that the resistivity of bedrock exhibits a clear tendency to decrease with increasing fracture frequency. Hydraulic conductivity shows a rather poor correlation with fracture frequency and resistivity. Crossplot technique is utilised to estimate fracture aperture from various data sets. The intensity of fracturing is estimated by means of fracture porosity obtained from resistivity data. Mise-à-la-masse method has turned out to be useful in mapping fractured zones within a short range. A one-dimensional thick sheet model is introduced to simulate fractured zones in the interpretation of mise-à -la-masse measurements. Geometrical and electrical parameters of the fractured zone are estimated by means of the computed model responses. An example of cross-correlation technique is presented to trace geological structures from borehole to borehole. Possibilities of defecting groundwater flow in bedrock are discussed. A quantitative method is presented to estimate the flow rate of water flowing along a fracture or a fractured zone.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages90
ISBN (Print)951-38-1792-X
Publication statusPublished - 1983
MoE publication typeNot Eligible

Publication series

SeriesValtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports


  • radioactive wastes
  • storage
  • geophysical surveys
  • boreholes
  • measurement


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