ESTIMATED AND OBSERVED SETTLEMENTS OF BRIDGE APPROACHES

MERCURY FILLED SETTLEMENT GAGES WERE INSTALLED ON THE ORIGINAL GROUND OF THE APPROACH EMBANKMENT FOUNDATION AT 4 SELECTED BRIDGE SITES; AND SETTLEMENT PLATES INSTALLED AT ONE OTHER BRIDGE SITE TO DETERMINE IF THE SETTLEMENT AT BRIDGE ABUTMENTS IS PRIMARILY A RESULT OF VOLUME CHANGES IN THE EMBANKMENT AND/OR FOUNDATION AND TO COMPARE OBSERVED AND PREDICTED FOUNDATION SETTLEMENTS. BY CONTINUALLY OBTAINING ELEVATIONS OF POINTS LOCATED ON THE PAVEMENT, SETTLEMENT OF THE PAVEMENT WAS OBTAINED. EMBANKMENT SETTLEMENT WAS TAKEN AS THE DIFFERENCE BETWEEN THE PAVEMENT SETTLEMENT AND FOUNDATION SETTLEMENT. UNDISTURBED SOIL SAMPLES WERE COLLECTED FROM THE FOUNDATION SOILS AT EACH OF THE FIVE SITES, AND CONSOLIDATION TESTS WERE PERFORMED ON THESE SAMPLES. THESE DATA AND TERZAGHI'S THEORY OF CONSOLIDATION WERE USED TO CALCULATE EXPECTED FOUNDATION SETTLEMENTS. THE FOLLOWING CONCLUSIONS WERE SUBSTANTIATED BY FINDINGS FROM FIELD AND LABORATORY INVESTIGATIONS: (1) THE ANALYSIS PROCEDURES USED ARE QUITE ADEQUATE FOR PREDICTING EMBANKMENT FOUNDATION SETTLEMENTS, (2) SETTLEMENT OF THE APPROACH FOUNDATION CAN CONTRIBUTE SIGNIFICANTLY TO SETTLEMENT OF BRIDGE APPROACHES; THE AMOUNT CONTRIBUTED IS HIGHLY DEPENDENT UPON THE TIME AT WHICH APPROACH PAVEMENT IS CONSTRUCTED, (3) SETTLEMENT OF THE EMBANKMENT CAN CONTRIBUTE SIGNIFICANTLY TO SETTLEMENT OF THE APPROACH PAVEMENTS, AND (4) THE RESULTS OF SETTLEMENT INVESTIGATION PERFORMED AT THE SITES OF PROPOSED BRIDGE CONSTRUCTION PROJECTS CAN PROVIDE A MUCH NEEDED BASIS FOR DESIGN TO CONTROL OR MINIMIZE THE EFFECT OF APPROACH SETTLEMENT.