TAKING INTO ACCOUNT THE SENSITIVITY OF THE SUBGRADE TO FROST AND THE THERMAL BEHAVIOUR OF THE PAVEMENT IN THE STUDY OF NEW PAVEMENTS

THIS REPORT DISCUSSES THE INTRODUCTION OF DATA ON THE SENSITIVITY OF SOIL AND THE THERMAL BEHAVIOUR OF PAVEMENTS IN THE STUDY OF THE LATTER. THE METHOD OUTLINED IS BASED ON THE CONCEPT OF INDEX AT SUBGRADE LEVEL AND IS USED AS FOLLOWS: (1) FOR A GIVEN INDEX AT THE SURFACE OF THE PAVEMENT, THE INDEX AT SUBGRADE LEVEL IS DETERMINED AS A FUNCTION OF THE THERMAL BEHAVIOUR OF THE PAVEMENT STUDIED; (2) THE INDEX OF THE SENSIVITY OF THE SUBGRADE TO IS DETERMINED. WITH THIS INDEX VALUE IT IS POSSIBLE TO DETERMINE THE VALUE OF THE INDEX TO WHICH THE SUBGRADE CAN BE SUBJECTED WITHOUT MARKED SWELLING AND EXCESSIVE LOSS OF BEARING CAPACITY DURING THAW. THIS IS CALLED THE SAFETY INDEX FOR THE SUBGRADE; (3) A COMPARISON IS MADE BETWEEN THE INDEX FOR THE SUBGRADE AND THE SAFETY INDEX. THE STATISTICAL STUDY OF CLIMATIC DATA SHOWS THAT IT IS HIGHLY PROBABLE THAT THE SAFETY INDEX WILL BE EXCEEDED EACH WINTER. TAKING INTO ACCOUNT THE LEVEL OF SERVICE DESIRED AND THE TYPE OF PAVEMENT CONSIDERED THE METHOD FACILITATES THE THERMAL PROTECTION OF THE SUBGRADE, THE EVALUATION OF THE FREQUENCY OF EXCEPTIONAL STRESSES IMPOSED ON THE PAVEMENT, AND THE ASSESSMENT OF THE FREQUENCY OF ROAD CLOSURES DUE TO THAW. THIS REPORT WAS PRESENTED AT THE OECD SYMPOSIUM ON FROST ACTION ON PAVEMENTS, OSLO, OCTOBER 1973.