LIAS CLAY: WEATHERING PROCESS AND THEIR EFFECT ON SHEAR STRENGTH

THE PROCESSES OF WEATHERING OF THE JURASSIC LIAS CLAY (A CLAY SHALE) AT FOUR DIFFERENT SITES ARE SHOWN TO RESULT IN A PROGRESSIVE CHANGE IN THE RELATION BETWEEN STRENGTH AND WATER CONTENT, WITH SUCCESSIVELY SHALLOWER, MORE WEATHERED LAYERS SHOWING HIGHER STRENGTHS AT A GIVEN WATE CONTENT. A WEATHERING SCHEME, RECOGNIZING FOUR WEATHERING ZONES, BASED ON THE DEGREE OF OXIDATION, APPEARS TO CORRESPOND WELL WITH THE STRENGTH-WATER CONTENT DATA. THE PROGRESSIVE CHANGES OF FABRIC OBSERVED IN PETROLOGICAL THIN SECTIONS OF THE CLAY CAN ALSO BE RELATED TO THESE WEATHERING ZONES. IT IS CONCLUDED THAT WEATHERING OF THE LIAS CLAY AFTER EXCAVATION IS SO SLOW ON AN ENGINEERING TIME SCALE THAT IT IS PROBABLY NOT AN IMPORTANT FACTOR LEADING TO LONG TERM SLOPE FAILURE. IN SUCH HEAVILY OVERCONSOLIDATED CLAYS THE SCATTER OF STRENGTH MAY BE AS MUCH ASSOCIATED WITH SMALL VARIATIONS IN WATER CONTENT AS WITH THE PRESENCE OF FISSURES. A FIFTH SITE PROVIDES AN EXAMPLE OF SEVERE DISTURBANCE OF THE LIAS CLAY RESULTING FROM PERMAFROST CONDITIONS DURING THE PLEISTOCENE, AND IT SHOWS THAT NOT ONLY DOES THIS DISTURBANCE LARGELY MASK THE EFFECT THAT WEATHERING HAS ON THE STRENGTH-WATER CONTENT RELATION BUT ALSO PROBABLY RESULTS IN A CONSIDERABLE REDUCTION IN EFFECTIVE STRESS STRENGTH PARAMETERS. /AUTHOR/

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: p. 403-31
  • Serial:
    • GEOTECHNIQUE
    • Volume: 22
    • Issue Number: 4
    • Publisher: Thomas Telford Limited
    • ISSN: 0016-8505

Subject/Index Terms

Filing Info

  • Accession Number: 00230439
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: TRIS
  • Created Date: Nov 18 1973 12:00AM