SEISMIC VELOCITY MEASUREMENTS FOR MODULI DETERMINATIONS IN TUNNELS

SEISMIC VELOCITY MEASUREMENTS ARE USED TO DETERMINE THICKNESS AND DYNAMIC MODULI VALUES OF LOOSENED ZONES OF TUNNEL WALL ROCK. THE ADVANTAGES OF THE ULTRASONIC METHOD ARE: (1) PRECISE TIMING THUS LEADING TO ACCURATE P WAVE VELOCITY VALUES, (2) DETECTION OF LOCAL CONDITIONS SUCH AS JOINTING, AND (3) DETERMINATION OF VERY LOCALIZED DATA CONDITIONS. THE DISADVATAGES ARE: (1) PREDRILLING OF NECESSARY HOLES, (2) FLUID FILLED HOLES FOR COUPLING, (3) SURFACE ZONE ACCURACY DIFFICULT TO EVALUATE, (4) THIN INTERMEDIATE VELOCITY ZONE OBSCURED BY WAVE PATH, AND (5) S WAVE VELOCITY DIFFICULT TO DETERMINE. THE ADVANTAGES OF THE SEISMIC REFRACTION METHOD ARE: (1) RAPID MEASUREMENT WITH VERY LITTLE PREPARATION NEEDED BEFOREHAND, (2) SURFACE ZONE EASY TO EVALUATE, (3) DEPTH PENETRATION EASY TO ACHIEVE BY ADJUSTING FIELD PROCEDURES, (4) ENERGY SOURCES AND DETECTORS READILY INITIATED TO IDENTIFY S WAVES, AND (5) THICKNESSES OF ZONES DETERMINED ALONG CONTINUOUS PORTIONS; THE DISADVANTAGES ARE (1) MINOR CONDITIONS AVERAGED WITHIN A SPECIFIC ZONE OR LAYER, (2) THIN INTERMEDIATE LAYERS MISSING, AND (3) INTERPRETATIVE PROCEDURES ARE REQUIRED TO EVALUATE SEISMOGRAM WAVE FORMS AND RECORD CHARACTERISTICS.

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 209-16
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00236535
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 11 1974 12:00AM