Abstract：The self-balanced testing method associated with stress gauges buried in shafts was applied to study the bearing behavior of 5 super long-large diameter piles for the 1-stage test project of Sutong bridge. The effects of grouting are (1) to eliminate the influence of technological defects，and recover the bearing capacities of strata，and (2) to improve the bearing capacities of piles. According to test results，the calculation values of ultimate bearing capacity of pile without sedimentation is increased for 34%～74%，and that of pile base is increased for 2%～153%. Compared with test results before grouting，the ultimate bearing capacity of pile is increased for 56%～100% after grouting，the total frictional resistance is increased for 12.39%～52.87% and the total base bearing capacity is increased for 4.91～25.67 times. After grouting，the ratio of base bearing capacity is increased from 1.88%～11.68% to 22.14%～34.67%，so that the bearing behavior of pile is improved greatly.
