REMEDIES AND TREATMENTS FOR THE FROST PROBLEM IN NEBRASKA

DAMAGING EFFECTS RESULTING FROM THE FREEZING AND THAWING OF BASE AND SUBBASE COURSES AND SUBGRADES ON NEBRASKA'S HIGHWAYS CAN BE CLASSIFIED UNDER TWO HEADINGS: (1) LOCAL FROST HEAVES, AND (2) WIDESPREAD REDUCTION IN ABILITY TO CARRY LOADS, CAUSING PERMANENT DEFORMATION OR ACTUAL BREAKUP. A TABLE INDICATES THE WIDE DIVERSITY OF MATERIALS IN WHICH FROST HEAVE MAY OCCUR IF THE SOIL LAYER IN QUESTION IS UNDERLAIN WITH A MORE IMPERVIOUS HORIZON. IT APPEARS THAT INCREASES IN THE MOISTURE CONTENT OF THE SUBGRADE SOIL IS AN IMPORTANT FACTOR. DESIGN TO ALLEVIATE THE EFFECTS OF FROST ACTION ARE DISCUSSED UNDER THE FOLLOWING HEADINGS: (1) SURFACE DRAINAGE, (2) SUBSURFACE DRAINAGE, (3) BASE AND SUBBASE COURSE THICKNESS, AND (4) BASE AND SUBBASE COURSE MIXTURES. TWO PRINCIPAL METHODS OF REPAIR OF FAULURES IN BITUMINOUS PAVEMENTS DUE TO FROST ACTION ARE EMPLOYED. THE METHOD USED HINGES ON THE CIRCUMSTANCES SURROUNDING THE FAILURE. ONE METHOD CONSISTS FO THE REMOVAL OF A DEPTH OF THE OFFENDING SUBGRADE MATERIAL AND THE REPLACEMENT OF THIS MATERIAL WITH SOIL OF BETTER QUALITY, BASE COURSE MIXTURE (GRANULAR), OR BITUMENIZED PATCHING MATERIAL. THE METHOD OF UNDERCUTTING AND WASTING POOR SUBGRADE MATERIAL IS ALSO EMPLOYED IN INSTANCES WHERE DEEP STRATA OF POOR SUBGRADE MATERIAL CAUSE FAILURES FOR SHORT DISTANCES. THE OTHER PRINCIPAL METHOD OF REPAIR OF BITUMINOUS PAVEMENTS AFTER FAILURE FROM FROST ACTION IS TO INCREASE THE TOTAL THICKNESS OF BASE AND SURFACE COURSES.