Abstract: The layers of a main tower construction site in Tianjin are mainly clay, silt and silt sand. Two groups of the super-long bored test piles with post pressure-grouting (a total of eight piles) are designed to take bearing behavior test using single pile vertical static load test of compression to master the engineering properties in the main tower construction site. Vibrating wire reinforcement meter and stratified settlement tube are installed to find out the pile side friction and the pile body layered settlement state. After the test, the results of the data analysis show that the pile side grouting can significantly improve the long pile side skin friction; pre-load pressure can enhance the flexibility of the super-long pile and reduce the settlement of the top of the pile in some degree. After unloaded stability, the test pile also has side resistance; the resistance of the upper segment is negative skin friction; and the lower segment is positive skin friction; and the pile body axial force causes the test pile to have some compression volume; that is an important part of the residual deformation.

Key words: super-long bored piles, bearing capacity of single pile, vertical static load test method of compression, pile shaft friction