PARTICLE SIZE ANALYSIS OF CLAY-CONTAINING SOILS

THE STANDARD METHODS USED FOR THE DETERMINATION OF THE PARTICLE SIZE DISTRIBUTION OF A SOIL ARE BASED ON THE ASSUMPTION THAT THE DIAMETER OF ANY SOIL PARTICLE WITHIN THE COARSE RANGE CAN BE MEASURED CORRECTLY ON SIEVES AND THAT STOKES'S LAW CAN BE APPLIED IN THE HYDROMETER ANALYSIS FOR THE DETERMINATION OF THE PARTICLE SIZE OF THE FINER FRACTIONS. TWO ANOMALIES HAVE BEEN OBSERVED MASKING STANDARD TEST RESULTS: (1) A PECULIAR SHARP CHANGE OF SLOPE WAS FOUND WHERE THE SIEVE AND HYDROMETER ANALYSIS CURVE SHOULD JOIN SMOOTHLY. THE HYDROMETER CURVE SHOWED A HIGH FINES CONTENT, THE CURVE BEING VIRTUALLY HORIZONTAL WHILE THAT OBTAINED BY SIEVING WAS RATHER STEEP IN THE TRANSITION ZONE. IT WAS FOUND THAT MONT-MORILLONITE CLAY MINERALS SWELL RAPIDLY DURING THE PROCESS OF HYDROMETER ANALYSIS, PRODUCING SUCH ABERRATION. FUTHER IT WAS FOUND THAT THE USE OF XYLENE OR SIMILAR LIQUID FOR HYDROMETER ANALYSIS RETARDED SWELLING SUFFICIENTLY TO PERMIT APPLICATION OF STOKES'S LAW. (2) ANOTHER ANOMALY ENCOUNTERED RECENTLY AS A DISCONTINUITY OF THE PARTICLE SIZE DISTRIBUTION CURVE, THE TWO PORTIONS (SIEVE AND HYDROMETER) NOT MEETING AT ALL. THE FEATURE MAY BE DESCRIBED AS A 'JUMP' IN THE CURVE AND AMOUNTED, IN THE CASE CONSIDERED, TO A DISCREPANCY OF SOME 25 PER CENT (BY WEIGHT) OF THE PERCENTAGE FINDER THAN 70 MICRONS AS MEASURED BY THE TWO METHODS. THIS WAS FOUND TO BE THE EFFECT OF A BOND (POSSIBLE DUE TO ELECTROSTATIC FORCES) BETWEEN KAOLINITE CLAY MINERALS AND QUARTZ GRAINS. THIS BOND COULD ONLY BE BROKEN BY GENTLE WORKING AT THE SAMPLE ON THE SIEVE. STANDARD AERATION, AS WELL AS NORMAL WASHING ONLY, WAS NOT SUFFICIENT TO SEPARATE THE PARTICLES. /ARTICLE/

• Supplemental Notes:
  • Vol Jg 11, NO 1 RS/19/69, P 5
• Publication Date: 0

Media Info

• Serial:
  • Via /South Africa/

Subject/Index Terms

• TRT Terms: Clay; Electrostatics; Fines (Materials); Force; Friction factor; Hydrometers; Montmorillonite; Sieve analysis; Soil particles; Spheres; Swelling; Swelling soils; Velocity
• Uncontrolled Terms: Particle size distribution
• Old TRIS Terms: Soil swell; Stokes law
• Subject Areas: Geotechnology; Highways;

Filing Info

• Accession Number: 00229860
• Record Type: Publication
• Source Agency: S African Council Sci Indus Research
• Files: TRIS
• Created Date: Sep 21 1970 12:00AM