COLLAPSIBLE SOILS IN LOUISIANA

IN SOUTHWEST LOUISIANA, SOME SURFACE SILTS (UP TO 3 FEET DEEP) COLLAPSE UNDER LOAD AFTER MOISTURE IS ADDED. THESE SOILS WERE INDISTINGUISHABLE FROM NEARBY NORMAL SILTS THROUGH ROUTINE TESTS. THE DEPOSITS OCCUR AS LOW, GENTLY- SLOPING RIDGES. VERY SIMILAR COLLAPSIBLE SOILS WERE FOUND IN THE WELL-KNOWN PIMPLE MOUNDS OF THE AREA. IN THE STABLE SILTS, VERMICULITE IS THE DOMINANT CLAY MINERAL; IN THE COLLAPSIBLE SILTS, MONTMORILLONITE, KAOLINE AND ILLITE ARE ALSO PRESENT. MOISTURE IS HELD IN THE PORES OF COLLAPSIBLE SILTS BY ELECTRO-CHEMICAL FORCES. WHEN COLLAPSIBLE SILTS WERE REMOLDED WITH WATER OR ETHYLENE GLYCOL (BOTH POLAR LIQUIDS), NO WATER PASSED THROUGH UNDER 2 METERS OF HEAD. IN SETTLED MIXTURES OF COLLAPSIBLE SILTS AND A SOLUTION OF CALGON, (COMMERCIAL BRAND OF SODIUM HEXAMETA PHOSPHATE) THE SUPERNATANT LIQUID WAS BLACK. THE COLOR CHANGE IS ATTRIBUTED TO LIGNINS. FOUR CRITERIA WERE ESTABLISHED FOR IDENTIFYING COLLAPSIBLE SILTS: AN IN-PLACE UNIT WEIGHT LESS THAN 80 LBS/CU FT; A MAXIMUM DRY UNIT WEIGHT LESS THAN 104 LBS/CU FT; A BLACK LIQUID AFTER THE SOIL SOLIDS HAVE SETTLED OUT IN A 3% SOLUTION OF CALGON; AND A TOTAL STRAIN OF AT LEAST 15% IN THE COLLAPSE TEST (A MODIFIED CONSOLIDATION TEST OF AN OVEN-DRIED, UNDISTURBED SAMPLE THAT IS THEN SATURATED UNDER PRESSURE TO 16 TONS/SQ FT).

  • Supplemental Notes:
    • APP
  • Corporate Authors:

    Louisiana State University and Agriculture & Mechanical College, Baton Rouge

    Baton Rouge, LA  USA  70803
  • Authors:
    • Arman, A
    • Thornton, S I
  • Publication Date: 1972

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 131 p.
  • Serial:
    • Issue Number: 111

Subject/Index Terms

Filing Info

  • Accession Number: 00230218
  • Record Type: Publication
  • Report/Paper Numbers: Bull
  • Files: TRIS
  • Created Date: Aug 5 1973 12:00AM