FROST PENETRATION: RELATIONSHIP TO AIR TEMPERATURES AND OTHER FACTORS

A REVIEW IS PRESENTED OF SOME OF THE BASIC CONSIDERATIONS OF FROST PENETRATION WITH REFERENCE TO ARTICLES EXPLAINING METHODS OF FROST DEPTH CALCULATIONS. FIELD MEASUREMENTS ARE ALSO PRESENTED WHICH PERMIT THE STUDY OF ONE OF THE IMPORTANT ASSUMPTIONS USED IN SUCH CALCULATIONS. THE PENETRATION OF FROST INTO A HIGHWAY SECTION IS A HEAT-FLOW PROCESS, THUS A GOOD STARTING POINT FOR DEPTH-OF-FREEZE CALCULATIONS IS A RECORD OF AIR TEMPERATURES. EQUATIONS UTILIZED FOR FROST DEPTH CALCULATIONS ARE REVIEWED. IT IS SHOWN THAT THE CALCULATION OF RATE OF THAW IS NOT NEARLY AS ADVANCED AS FROST PENETRATION PROCEDURES. STUDIES OF FROST MEASUREMENTS INDICATE THAT THE FREEZE DEPTHS DO NOT VARY IN ACCORDANCE WITH THE CONCEPT OF THE STEFAN EQUATION IN SHOWING EQUAL DEPTHS FOR A GIVEN MAGNITUDE OF DEGREE-DAYS ACCUMULATED IN VARYING PERIODS OF TIME FOR DIFFERENT WINTERS.