HOW RELIABLE IS THE FACTOR OF SAFETY IN FOUNDATION ENGINEERING

A STUDY WAS MADE OF THE VARIABILITY IN SOIL PARAMETERS DUE TO TESTING TECHNIQUES. IT WAS SHOWN THAT THE VARIABILITY OF COHESION INTERCEPT WAS LARGER THAN THAT OF ANGLE OF FRICTION IN THE CASE OF THE COULOMBIAN SHEAR STRENGTH CONCEPT. FOR A GIVEN LOADING SYSTEM AND GIVEN GEOMETRY, THE FACTOR OF SAFETY IS A FUNCTION OF SHEAR STRENGTH PARAMETERS OF THE SOIL. THE COEFFICIENT OF VARIATION OF FACTOR OF SAFETY WAS STUDIED AND THE REQUIRED FACTOR OF SAFETY FOR DIFFERENT CONFIDENCE LIMITS INVESTIGATED. THIS WAS DONE FOR EARTH PRESSURES ON RETAINING STRUCTURES. FOR BEARING CAPACITY PROBLEMS, AND FOR SLOPE STABILITY ANALYSIS. THE STUDY SHOWS THAT TYPICAL FACTORS OF SAFETY USED IN FOUNDATION ENGINEERING RESULT IN A CONFIDENCE LEVEL OF 90 - 99.9 PERCENT AND THAT THE SEEMINGLY DIFFERENT FACTORS OF SAFETY MAY HAVE SIMILAR CONFIDENCE LEVELS. /TRRL/