PORE STRUCTURE OF FRIABLE LOESS WITH DISCUSSION

THE SIZE, SHAPE, AND ARRANGEMENT OF UNIVERSAL GRAINS COMPOSING A SOIL MASS, REFERRED TO AS STRUCTURE, HAVE PROFOUND INFLUENCE ON THE ENGINEERING BEHAVIOR OF SOIL. THESE ENGINEERING ASPECTS CONCERN SENSITIVE SOILS, COMPRESSIBILITY, AND PERMEABILITY. IN ADDITION THERE ARE TWO LIMITATIONS INHERENT IN STUDYING SOIL MECHANICS AND STRUCTURE: (1) SOIL STRUCTURES ARE NOT CLEARLY DEFINED, AND (2) SOIL STRUCTURES LACK SUFFICIENT QUANTIFICATION. MERCURY-INJECTION IS PROPOSED AS A MEANS OF DESCRIBING THE PORE-SIZE DISTRIBUTION OF FRIABLE LOESS IN UNDISTURBED AND COMPACTED STATES. THIS METHOD IS BASED ON THE WASHBURN EQUATION WHICH GIVES THE PRESSURE REQUIRED TO FORCE MERCURY INTO CAPILLARY PORES. THE PORE-SIZE DISTRIBUTION OF SAMPLES COMPACTED TO ESSENTIALLY THE SAME VOID RATIO AS THE FIELD CONDITION SHOWS FEWER LARGE-SIZE PORES AND, IN GENERAL, A MORE UNIFORM DISTRIBUTION OF PORE SIZES THAN THE UNDISTURBED SAMPLES. LOESS SAMPLES COMPACTED TO VARIOUS DENSITIES AT OPTIMUM MOISTURE CONTENT SHOW THAT THERE IS A DECREASE IN MEAN PORE SIZE WITH INCREASING COMPACTION AND THAT THE MAJOR REDUCTION IN PORE VOLUME IS ACHIEVED BY REDUCING THE LARGER PORES. A COMPARISON OF SCANNING ELECTRON MICROGRAPHS AND CURVES OF GRAIN-SIZE DISTRIBUTION REVEALS THAT VARIOUS TYPES OF LOESS STRUCTURES CAN BE CLASSIFIED. THE 3 PREVALENT STRUCTURES IN LOESS ARE THE PARTICULATE IN WHICH PRIMARY GRAINS ARE IN CONTACT AND THE VOIDS ARE IN GENERAL MUCH SMALLER THAN THE GRAINS, THE COMPOSITE IN WHICH THE PRIMARY GRAINS ARE AGGREGATED INTO SECONDARY CLUSTERS AND THE SIZES OF FEW VOIDS ARE LARGER THAN THE GRAINS, AND THE HONEYCOMB IN WHICH THE GRAINS FROM ARCHES OVER MANY LARGE VOIDS. VOID RATIO AND POROSITY ARE 2 COMMON PARAMETERS USED BY SOIL ENGINEERS TO GIVE SOME INDICATION OF STRUCTURE; HOWEVER, A COMPARISON OF THE DATA SHOWS THAT DIFFERENT SOILS MAY HAVE THE SAME VOID RATIO BUT VERY DIFFERENT PORE-SIZE DISTRIBUTIONS. THE PORE-SIZE DISTRIBUTION MAY BE AS IMPORTANT AS THE OTHER PARAMETERS, OR POSSIBLY MORE SO, IN EXPLAINING THE MECHANISTIC BEHAVIOR OF SOIL INSOFAR AS IT IS ONE MEANS OF QUANTIFYING SOIL STRUCTURE. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 14-25
  • Monograph Title: Soils: loess, suction and frost action
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00238142
  • Record Type: Publication
  • ISBN: 0309021588
  • Files: TRIS, TRB
  • Created Date: Sep 28 1973 12:00AM