At a building site where the soil consisted of a quick clay with undisturbed shear strength as low as 0.7 t/m2 the planned deep excavations could not be performed due to expected upheavel of the bottom of the excavation. It was then decided to try to increase the shear strength of the quick clay by electro-osmotic consolidation. A description is given of the performed laboratory tests that enabled the design of the field installations to be made. On an area of 200 m2 190 electrodes of 19 mm iron reinforcement rods were driven down to a depth of 9,6m, where equipment for measuring settlements and pore pressures was installed. The electro-osmotic consolidation lasted for 180 days, and the current was in mean 250 amperes at 40 volts. The settlements in the first period corresponded very closely to what could be calculated from the laboratory tests. After 30 days when the total settlements amounted to 21 cm a cane boring midway between anode and cathode showed a marked decrease in shear strength. Values as low as 0,3 t/m2 were measured. In spite of this it was decided to continue the treatmtent. After 103 days when the total settlement was 47 cm a new vane boring showed a sufficient increase in shear strength to permit excavation. After the completion of the excavation the opportunity was taken to investigate a horizontal profile between anode and cathode rows. The shear strength close to the anode was found as high as 12 t/m2 decreasing towards the cathode to 1 t/m2. In the same direction there had also been a decrease in water content and an increase in plastic index.

  • Corporate Authors:

    Norwegian Geotechnical Institute

    Forsknings Veien
    Oslo 3,   Norway 
  • Authors:
    • Moum, J
  • Publication Date: 1966

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Filing Info

  • Accession Number: 00263620
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 9 1975 12:00AM