INFLUENCE OF SOIL'S PHYSICAL NATURE ON ITS MECHANICAL BEHAVIOUR; SIGNIFICANCE OF ATTERBERG LIMITS AS REGARDS SOIL BEHAVIOUR

THE MECHANICAL BEHAVIOUR OF A SOIL AS A FUNCTION OF THE MOISTURE CONTENT CAN BE CHARACTERIZED BY ITS ATTERBERG LIMITS. THE VARIATION IN THESE LIMITS AS A FUNCTION OF THE SOIL TEXTURE HAS BEEN STUDIED ON A LARGE NUMBER OF SAMPLES VARYING IN ORIGIN, BY ESTABLISHING MULTIPLE REGRESSION EQUATIONS FOR EACH TYPE OF SOIL. IT APPEARS THAT THE INFLUENCE OF A GRADING CLASS IS ALL THE MORE IMPORTANT AS IT DOES NOT OCCUR VERY OFTEN. THIS CAN BE EXPRESSED BY AN EQUATION OF THE FOLLOWING TYPE; IP=50 (LOG A%/10)-10 (LOG MO%/1.5). THE INFLUENCE OF CLAY IS MARKEDLY IMPORTANT. SILT AND SAND HAVE A GENERALLY OPPOSED WEAKER EFFECT. ORGANIC MATTER ACTS AS A COMPENSATING ELEMENT BY REPLACING CLAY, WHEN THE LATTER IS ABSENT, WITH A SPECIFIC ACTION 7 OR 8 TIMES STRONGER AND BY MODERATING THE PLASTIC CHARACTERISTICS OF EXCESSIVELY HEAVY MATERIALS. ATTERBERG LIMITS CAN BE USED: FOR STRUCTURAL STABILITY (IT IS POSSIBLE TO DETERMINE THE MINIMUM ORGANIC MAINTENANCE), FOR SOIL BEHAVIOUR (IT IS POSSIBLE TO GO FURTHER THAN A SIMPLE CLASSIFICATION OF SOILS ACCORDING TO THEIR FLEXIBILITY OF USE, AND TO FORECAST THE AFFECT OF THE EQUIPMENT UNDER GIVEN CONDITIONS).