PHENOMENON AND MECHANISM OF FROST HEAVING

A MECHANISTIC EXPLANATION IS PRESENTED OF FROST ACTION IN SOILS, BASED ON THE HYPOTHESIS THAT LIQUID FILMS EXISTING BETWEEN PARTICLES AND AN ICE LENS ARE THE FOCAL CENTERS OF ENERGY FOR THE HEAVING (WORK) PROCESS. HEAVING, UPON FREEZING, IS NOT A UNIQUE PROPERTY OF SOIL PARTICLES AND WATER; LENSING AND SEGREGATION OCCUR WITH OTHER POWDERED MATERIALS AND OTHER LIQUIDS. AN EXPLANATION OF THE DEVELOPMENT OF SUCTION FORCES IN UNFROZEN LIQUID BELOW THE ICE LENS IS PRESENTED AND EXPERIMENTAL DATA ARE PROVIDED FOR TOW CASES-A CLOSED SYSTEM AND AN OPEN SYSTEM. THE EFFECT OF HEAT EXTRACTION RATE AND FREEZING PENETRATION RATE OF HEAVING IS DISCUSSED. EXPERIMENTAL LABORATORY DATA INDICATE TWO CIRTICAL RATES OF FREEZING: (1) MAXIMUM HEAVE RATE, AND (2) MINIMAL HEAVE RATE EQUAL TO VOLUME EXPANSION OF IN SITU (VOID) WATER. HEAVE RATE AND WORK OF HEAVING AND THEIR DEPENDENCE ON FREE ENERGY GENERATION DURING FREEZING ARE DISCUSSED IN GENERAL TERMS. TYPICAL EXPERIMENTAL DATA ARE PRESENTED ILLUSTRATING THE REDUCTION IN HEAVE RATE WITH INCREASE EXTERNAL (AND INTERNAL) RESISTANCE. THE ROLE OF SOIL STRUCTURE IN FROST SUSCEPTIBILITY IS DISCUSSED. CHANGES IN FROST HEAVING RATES CAN BE EFFECTED BY ADDITION OR REMOVAL OF EITHER, OR BOTH, THE COARSE AGGREGATE OR SOIL FINES. SUGGESTIONS ARE OFFERED FOR APPROACHES TO SOIL MODIFICATION TO REDUCE HEAVING. EASILY UNDERSTANDABLE MECHANISTIC DESCRIPTION OF THE FROST HEAVING PHENOMENON AND THE SIMULTANEOUS PRESENCE OF PRESSURE AND SUBPRESSURE IN THE SYSTEM IS PRESENTED AND THE IMPORTANT SOIL PARAMETERS INVOLVED IN FROST HEAVING ARE POINTED OUT. /AUTHOR/