PRESSURES DEVELOPED IN A POROUS GRANULAR SYSTEM AS A RESULT OF ICE SEGREGATION

RECENT EXPERIMENTS SHOW THAT THE MAGNITUDE OF SUCTION (SOIL MOISTURE TENSION) AT THE ICE/WATER INTERFACE, WHEN THE GROWTH OF THE ICE LENS STOPS, DEPENDS UPON THE DIMENSIONS OF THE PORE SYSTEM IN THE SOIL. EXPERIMENTALLY DETERMINED RELATIONSHIPS ARE PRESENTED BETWEEN OVERBURDEN PRESSURES AND THE MAGNITUDE OF THE SOIL MOISTURE TENSION WHEN THE ICE LENS GROWTH HAS DECREASED TO ZERO UNDER EQUILIBIRUM CONDITIONS. THE MECHANISM OF ICE LENSING IS DISCUSSED IN LIGHT OF THE EXPERIMENTAL RESULTS. THE GRANULAR SYSTEM USED CONSISTED OF POWDERED QUARTZ. THE SPECIMENS WERE PREPARED AT VARIOUS DENSITIES IN A HARVARD MINIATURE COMPACTION APPARATUS BY CONTROLLING THE MOISTURE CONTENT AND COMPACTIVE EFFORT. THE SPECIMENS WERE FROZEN UNIDIRECTIONALLY, SIMILAR TO THE FREEZING OF SOILS IN NATURE. THE MAXIMUM SOIL MOISTURE TENSIONS INDUCED BY THE GROWTH OF THE ICE LENS WERE DETERMINED FOR THREE DIFFERENT OVERBURDEN PRESSURES: 23, 229, AND 535 GM. PER SQ CM. THE EQUILIBRIUM CONDITIONS WITH RESPECT TO OVERBURDEN PRESSURES AND SOIL MOISTURE TENSIONS ARE SUMMARIZED FOR THE PARTICUALR GRANULAR MATERIAL USED: (1) THE MAXIMUM MOISTURE TENSION INDUCED IN THE UNFROZEN PORTION DUE TO ICE SEGREGATION DECREASES WITH INCREASING OVERBURDEN PRESSURES, (2) THE GREATER THE PACKING DENSITY OF THE GRANULAR MATERIAL, THE HIGHER THE MOISTURE TENSION INDUCED AT THE SAME OVERBURDEN PRESSURE, (3) FROST HEAVING DUE TO ICE SEGREGATION CAN BE LIMITED EITHER BY THE DEVELOPMENT OF A SUFFICEINTLY HIGH MOISTURE TENSION, BY APPLICATION OF OVERBURDEN PRESSURES, OR BY A COMBINATION OF BOTH, AND (4) EXPRESSED IN GM. PER SQ CM. THE LIMITING MOISTURE TENSION IS ABOUT HALF THE LIMITING OVERBURDEN PRESSURE. A DIAGRAM WAS CONSTRUCTED SHOWING THE RELATIVE POSITION OF THE ICE/WATER INTERFACE AND ICE LENS WITH RESPECT TO STRUCTURE OF THE PORE SYSTEM. A SAMPLE CALCULATION IS PRESENTED TO ILLUSTRATE THE MAXIMUM PRRESSURE REQUIRED TO STOP ICE LENS' GROWTH WHEN THE SYSTEM REMAINS SATURATED. THE THEORY PREDICTS THAT ICE LENS MAY BE HALTED BY OVERBURNED PRESSURE, BY TENSION IN THE PORE WATER, OR A COMBINATION OF BOTH. THIS WAS SHOWN TO BE POSSIBLE EXPERIMENTALLY.

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  • Accession Number: 00237883
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 17 1970 12:00AM