STABILITY OF BRIDGE PIERS

THE STABILITY OF BRIDGE PIERS IS DEPENDENT ON: (1) THE SUPPORTING EARTH BELOW THE FOUNDATION AND (2) THE EARTH SURROUNDING THE PIER SHAFT WHERE SUBSURFACE EXPLORATIONS SHOW THAT THE COHESIVE SOILS UNDER THE PIER ARE DEEP. THE PIER IS CONSIDERED STABLE WHEN THE BASE FALLS WITHIN THE MIDDLE THIRD AND THE MAXIMUM SOIL PRESSURE DOES NOT EXCEED SOME PRESUMPTIVE UNIT VALUE, WHICH IS CONSIDERED TO BE SAFE FOR THE GIVEN SOIL. AN ANALYSIS OF SOIL CONDITIONS SHOULD REVEAL: (1) THE VARIATION OF THE INITIAL STRESS CONDITIONS IN THE SOIL; (2) THE VARIATION OF COMPRESSIBILITY OF THE DIFFERENT SOIL LAYERS IN THE DEPOSIT; (3) THE VARIATION OF THE SHEARING CHARACTERISTICS OF THE SOIL AS DEFINED BY THE NATURAL SHEAR STRENGTH UNDER THE PRE-CONSOLIDATION LOAD AND BY THE APPARENT ANGLE OF INTERNAL FRICTION; AND (4) THE DETERMINATION OF THE RATE OF SETTLEMENT AS DEFINED BY THE COEFFICIENT OF CONSOLIDATION.