THE APPLICATION OF GEOPHYSICAL METHODS TO GRADING AND OTHER HIGHWAY CONSTRUCTION PROBLEMS

FOR DETERMINING THE PRESENCE AND LOCATION OF SOLID ROCK FOUNDATIONS, AND FOR CLASSIFYING SOILS AND OTHER UNDERLYING STRATA WITH REPECTS TO THEIR RELATIVE DEGREES OF COMPACTION, THE SEISMIC METHOD IS MORE DEPENDABLE THAN THE ELECTRICAL RESISTIVITY METHOD AND HAS AN INHERENT ADVANTAGE OVER ALL OTHER METHODS NOW USED, IN THAT IT MEASURES DIRECTLY THE RIGIDITY OF THE EARTH'S CRUST. A BLASTING CAP OR SMALL CHARGE OF DYNAMITE EXPLODED AT OR UNDER THE SURFACE OF THE GROUND BECOMES THE CENTER OF A WAVE DISTURBANCE. SENSITIVE MICROPHONE DETECTORS PLACED AT DIFFERENT DISTANCES FROM THE SHOT PICK UP THE DISTURBANCE SUCCESSIVELY AND TRANSMIT THE ELECTRIC IMPULSES TO GALVANOMETERS WHICH RECORD THEM AS LIGHT TRACES ON A MOVING PHOTOGRAPHIC FILM. BY MEANS OF AN ACCURATE TIMING MECHANISM THE TIME OF TRANSIT OF THE WAVE DISTURBANCE FROM THE SHOT POINT TO EACH DETECTOR IS ALSO INDICATED ON THE FILM, THE SPEED OF TRANSIT BEING INDICATIVE OF THE ELASTIC CHARACTER OF THE MATERIAL TRAVERSED. DATA FROM A NUMBER OF SHOTS ARE PLOTTED ON A TIME-DISTANCE CURVE, AND THE RELATIVE RIGIDITIES OF THE UNDERLYING MATERIALS THEREBY CLASSIFIED. THE THICKNESS OF SURFACE LAYERS OF SOFT MATERIAL OVER DENSER LAYERS OF CLAY OR SHALE ARE INDICATED, AND LIKEWISE THE DEPTH TO MATERIAL OF STILL GREATER RIGIDITY, SUCH AS SOLID ROCK. /AUTHOR/

  • Supplemental Notes:
    • Vol 16, pp 282-293, 12 FIG
  • Authors:
    • Shepard, E R
    • BERNHARD, R K
    • Teller, L W
    • Buchanan, J A
  • Publication Date: 1937

Media Info

  • Monograph Title: Proceedings of the Sixteenth Annual Meeting of the Highway Research Board Held at Washington, D.C. November 18-20, 1936
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00229833
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 15 1971 12:00AM