A FIELD METHOD FOR MEASURING THE PERMEABILITY OF SOIL BELOW A WATER TABLE

THE METHOD INVOLVES THE INSERTION OF A TUBE INTO THE SOIL TO THE DEPTH WHERE THE MEASUREMENT IS DESIRED, THE REMOVAL OF THE SOIL FROM THE TUBE, THE EMPTYING OF THE WATER IN THE TUBE TO A KNOWN DISTANCE BELOW THE WATER TABLE LEVEL, AND THE MEASURING OF RISE OF WATER IN THE TUBE IN A KNOWN TIME. THE PERMEABILITY IS DETERMINED IN STANDARD UNITS USING A FORMULA BASED ON DARCY'S LAW. THE FORMULA INVOLVES THE RADIUS OF THE TUBE, THE DEPTH OF THE TUBE BELOW THE WATER TABLE, AND A CERTAIN CONSTANT OBTAINED IN THE LABORATORY. THE CONSTANT, EVALUATED IN THE LABORATORY, DEPENDS UPON THE RADIUS AND DEPTH OF THE TUBE. IT WAS DETERMINED BY A THREE DIMENSIONAL ELECTRIC ANALOGUE OF ITS GROUND WATER FLOW SYSTEM, THE GROUND WATER FLOW HAVING BEEN SIMULATED BY A CORRESPONDING ELECTRIC CURRENT FLOW. THE ANALOGUE WAS ALSO USED TO OBTAIN THE STREAMLINE PATTERN, AND LINES OF EQUAL HYDRAULIC HEAD, AND TO EVALUATE CHANGES IN THE RATE OF FLOW DUE TO OBSTRUCTIONS, SUCH AS ROCKS, WHICH MAY BE NEAR THE END OF A TUBE. THE ANALOGUE WAS USED BECAUSE A MATHEMATICAL ANALYSIS OF THE PROBLEM IS NOT AT HAND. THE EFFECT OF ROCKS AND OTHER OBSTRUCTIONS ON THE ACCURACY OF THE MEASUREMENTS WAS FOUND TO BE SMALL. THE FIELD EQUIPMENT CONSISTS OF APPARATUS FOR DRIVING THE TUBES QUICKLY, FOR REMOVING THE SOIL FROM THE TUBES WITHOUT PUDDLING THE EXPOSED SOIL SURFACE, FOR MEASURING THE WATER LEVELS, AND FOR PULLING THE TUBES FROM THE SOIL. EIGHT INCH DIAMETER TUBES WERE USED. SOME FIELD DATA ARE ALSO REPORTED. STATISTICAL METHODS WERE USED TO DETERMINE, FROM THE DATA, THE NUMBER OF TUBES REQUIRED TO OBTAIN MEASUREMENTS OF A REASONABLE DEGREE OF ACCURACY. THE RESULTS INDICATE THAT PERMEABILITY DETERMINATIONS AT DEPTHS OF 6 IN. OR LESS ARE DIFFICULT TO DUPLICATE AND ARE OF DOUBTFUL VALUE. AT DEPTHS OF 12 IN. OR MORE, SATISFACTORILY UNIFORM RESULTS WERE OBTAINED. TWO ADDITIONAL METHODS OF PERMEABILITY MEASUREMENT ARE BRIEFLY DESCRIBED. THE FIRST, A MODIFICATION OF THE ABOVE METHOD, INVOLVES DRIVING TUBES 1 IN. IN DIAMETER INTO THE SOIL, AND REMOVING THE SOIL TO A DEPTH 4 IN. BELOW THE TUBE WITH A CONVENTIONAL SOIL AUGER. THE SECOND METHOD MEASURES PERMEABILITY BY OBSERVING THE RATE AT WHICH A HOLE, DUG WITH A POST HOLE AUGER, FILLS WITH WATER. IN BOTH THE LATTER METHODS THE ELECTRIC ANALOGUE WAS USED TO OBTAIN FACTORS TO CONVERT MEASURED VALUES TO STANDARD PERMEABILITY UNITS. /AUTHOR/

  • Supplemental Notes:
    • Vol 28, pp 433-442, 12 FIG, 1 TAB, 12 REF
  • Authors:
    • Frevert, R K
    • Kirkham, D
  • Publication Date: 1949

Media Info

  • Monograph Title: Proceedings of the Twenty-Eighth Annual Meeting of the Highway Research Board Held at Washington, D.C. December 7-10, 1948
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00235976
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 27 1971 12:00AM