TESTING PILES FOR THE SECOND STAGE OF NORTH BRIDGE APPROACH OF SUTONG YANGTZE RIVER BRIDGE

Static load tests were carried out with the self-balanced test method on four bored piles of which two use the U-tube base grouting technique, for the second stage of the north bridge approach at the Sutong Yangtze River Bridge. The test results of the pile-tip bearing capacity are about 5% to 25% smaller than the calculation results from the standard. The critical displacements of un-grouted piles are 16 mm and 38 mm respectively, which are larger than those of the grouted piles: 12 mm and 21 mm respectively. The pile-tip bearing capacity for the grouted piles is 2.46 to 3.32 times of that of the un-grouted ones, or 2.46 to 2.50 times of the calculated value from the standard. After grouting, ratios of the pile-tip bearing capacity over total capacity increase from 14.42%15.39% to 22.83%27.22%. The shaft resistances are also affected by grouting. The apparent affecting zone ranges from 14.27 m to 19.12 m above the pile tip with reduced critical displacements.