INFLUENCE OF SOIL SUCTION ON BEHAVIOR OF A GLACIAL TILL SUBJECTED TO REPEATED LOADING

FIELD AND LABORATORY INVESTIGATIONS ARE DESCRIBED OF THE INFLUENCE OF SOIL MOISTURE SUCTION ON THE RESILIENCE CHARACTERISTICS OF A GLACIAL TILL FROM SOUTHERN SASKATCHEWAN, CANADA. DEFLECTIONS UNDER AN 18,000-LB AXLE LOAD WERE MEASURED IN THE FIELD BY A BENKELMAN BEAM ALONG A 10-MILE SECTION OF PROVINCIAL HIGHWAY. TWENTY GYPSUM BLOCK MOISTURE METERS WERE PLACED 24 INCHES BELOW THE PAVEMENT SURFACE IN THE TILL SUBGRADE WHERE THE PAVEMENT SURFACE WAS IN GOOD CONDITION. RESULTS INDICATED THAT DEFLECTIONS GENERALLY CORRESPONDED TO SOIL SUCTION MEASUREMENTS, E.G., FOR COMPARATIVELY LARGE VALUES OF SOIL SUCTION THE DEFLECTIONS WERE COMPARATIVELY SMALL. SOIL SUCTION MEASUREMENTS AND REPEATED LOAD TRIAXIAL COMPRESSION TESTS WERE PERFORMED IN THE LABORATORY ON SAMPLES OF THE TILL COMPACTED BY STATIC COMPACTION OVER A RANGE IN WATER CONTENTS. WHEN THE SAMPLES WERE COMPACTED WET OF OPTIMUM FOR THE PARTICULAR COMPACTIVE EFFORT, THE SUCTION VALUES WERE LOW AND RESILIENT MODULI, DETERMINED FROM THE REPEATED LOAD TESTS, WERE COMPARATIVELY SMALL. COMPACTED DRY OF OPTIMUM, ON THE OTHER HAND, THE SUCTION VALUES WERE HIGH AND THE MODULI, CORRESPONDINGLY, WERE LARGE. THE INVESTIGATION INDICATED THAT THE VALUES OF SUCTION MEASURED IN THE FIELD COULD BE DUPLICATED IN THE LABORATORY WITH AVAILABLE EQUIPMENT AND THAT WHILE THE RANGE IN SUCTION WAS NOT LARGE (0 TO 110 PSI) THE RANGE IN MODULI (2000 TO 22,000 PSI) MAY BE OF CONSIDERABLE SIGNIFICANCE IN DESIGN. THE DATA ALSO EMPHASIZE THAT, FOR DESIGN OF PAVEMENTS, ONE MUST CONSIDER NOT ONLY MATERIAL CHANGES, BUT ALSO POTENTIAL SIGNIFICANT CHANGES IN SOIL SUCTION FOR THE SAME MATERIAL. /AUTHOR/