DESICCATION OF SOILS DERIVED FROM VOLCANIC ASH

Five volcanic-ash-derived soils from the island of Hawaii were studied to determine the relation of changing moisture content to engineering behavior. Two soils weathered on the leeward side of the island under relatively dry conditions; the other three developed on the windward side under high mean annual rainfalls. The dry soils show little change on desiccation whereas the desiccation of the wet soils is accompanied by an irreversible hardening that causes drastic changes in the index properties. Engineering behavior of the dry soils is similar to that of a sandy silt. The wet soils behave as plastic clays but, when they are dried out, their engineering characteristics change to those of a sand. Mercury porosimetry tests reveal that, in wet soils, volume changes between field mositure content and the oven-dry state are about 150 percent. The dry soils exhibit very small volumetric shrinkage. Drying tests under controlled relative humidity provide data on drying rates and critical moisture contents. The mineralogy of the soils was studied by using X-ray diffraction and fluorescence, differential thermal, and thermogravimetric analyses. The predominant minerals are gibbsite, iron oxides, and allophane. Mineralogical studies indicate that irreversible hardening is accompanied by an increase in gibbsite content. Mercury porosimetry results and mineralogical analysis indicate that a major portion of the shrinkage is due to contraction of the intermediate-size pores and that the extent of shrinkage is a function of allophane content. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 44-49
  • Monograph Title: Soil taxonomy and soil properties
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00179010
  • Record Type: Publication
  • ISBN: 0309026717
  • Files: TRIS, TRB
  • Created Date: Aug 19 1978 12:00AM