NUCLEAR APPARATUS FOR DENSITY AND MOISTURE MEASUREMENTS

THE USE OF GAMMA RADIATION FOR MEASURING THE BULK DENSITY OF MATERIALS AND OF NEUTRONS FOR DETERMINING MOISTURE CONTENT HAS RECEIVED ATTENTION IN MANY COUNTRIES IN RECENT YEARS. APART FROM THE DEEP PROBE APPARATUS DESIGNED FOR MEASUREMENTS AT DEPTH, TWO BASIC FORMS OF EQUIPMENT HAVE BEEN DEVELOPED FOR USE IN SURFACE LAYERS OF MATERIALS; THESE ARE COMMONLY KNOWN AS THE DIRECT TRANSMISSION TYPE FOR THE MEASUREMENT OF BULK DENSITY AND THE BACK-SCATTER TYPE FOR THE MEASUREMENT OF BOTH DENSITY AND MOISTURE CONTENT. DETAILED STUDIES HAVE BEEN CARRIED OUT WITH BOTH THESE TYPES OF EQUIPMENT TO DETERMINE THE ACCURACY WITH WHICH THE DENSITY AND MOISTURE CONTENT OF COMPACTED LAYERS OF SOIL CAN BE OBTAINED. THE MORE IMPORTANT ASPECTS OF THIS WORK DESCRIBED IN THE PAPER ARE' 1. VOLUME OF SOIL SAMPLED BY THE EQUIPMENT. 2. EFFECT ON THE RESULTS OF DENSITY GRADIENTS IN THE TEST LAYER. 3. EFFECT OF THE TYPE OF MATERIAL ON THE CALIBRATION OF THE EQUIPMENT. THE INVESTIGATIONS SHOWED THAT THE RESULTS GIVEN BY THE BACK-SCATTER TYPE OF EQUIPMENT ARE LARGELY DETERMINED BY THE STATE OF COMPACTION AND MOISTURE CONTENT OF THE TOP INCH OR SO OF THE LAYER. CONSEQUENTLY THE APPARATUS WILL GIVE SERIOUS ERRORS IF USED TO MEASURE THE STATE OF COMPACTION OR MOISTURE CONTENT OF LAYERS HAVING LARGE GRADIENTS OF DENSITY OR MOISTURE CONTENT. ON THE OTHER HAND THE DIRECT TRANSMISSION TYPE OF APPARATUS WAS FOUND TO MEASURE THE MEAN DENSITY OF THE DEPTH PENETRATED BY THE PROBE. WITH BOTH TYPES OF EQUIPMENT THE CALIBRATION FOR DENSITY WAS AFFECTED BY THE TYPE OF MATERIAL AND THE USE OF A MEAN CALIBRATION LINE COULD INTRODUCE ERRORS OF PLUS OR MINUS 5 LB/CU. FT WITH SOME COMMON MATERIALS. AN EXPLANATION IS GIVEN FOR THE CAUSE OF THE SOIL-TYPE EFFECT. THE MAIN ADVANTAGE OF THE RADIATION EQUIPMENT OVER THE SAND REPLACEMENT METHOD OF DETERMINING DRY DENSITY AND MOISTURE CONTENT IS THAT RESULTS ARE OBTAINED SOON AFTER THE TESTS ARE COMPLETED, BUTH THE EQUIPMENT IS MUCH MORE COSTLY AND A HIGHER GRADE OF TESTING STAFF IS REQUIRED. /RRL/

• Supplemental Notes:
  • Vol43, No506, PP37-43, 11FIG, 1TAB, 2REF
• Authors:
  • Lewis, W A
• Publication Date: 1965-2

Media Info

• Serial:
  • Roads & Road Construction, London /UK/

Subject/Index Terms

• TRT Terms: Accuracy; Analysis; Backscattering; Bulk density; Calibration; Costs; Density; Equipment; Gamma rays; Humidity; Measuring instruments; Moisture content; Neutrons; Nuclear phenomena; Nuclear tests; Soil compaction; Soil densification; Soil water; Soils; Tests; Texture
• Old TRIS Terms: Direct; Equipment cost; Measuring apparatus; Nuclear; Nuclear moisture-density determinations
• Subject Areas: Finance; Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00216026
• Record Type: Publication
• Source Agency: Road Research Laboratory /UK
• Files: TRIS
• Created Date: Jan 18 1994 12:00AM