The law of variation of ultimate vertical bearing capacity and shaft resistance and tip resistance of wedge pile by compressive loading on the top is mainly studied in this paper.

In order to probe into the feasibility of using wedge piles in Tianjin area,this paper studies the law of the variation of ultimate vertical bearing capacity,shaft resistance and tip resistance of a wedge pile by compressive loading on the top.

By the static loading test of the large diameter bored cast-in-place pile,in which stressometers and deformeters are inbuilted at the pile s differrnt positions such as the bottom,the interfaces for soil layers along pile and so on,the loading transmission mechanism,the regulations of axial force and the skin friction of pile are analyzed.

Based on Mindlin stress solution, the calculating method of additional stress in foundation soil for any distribution form of the skin friction of pile is deduced in this paper, and the settlement problem of single pile is analyzed.

The bearing performance of pile is studied, including uplifting displacement, load transfer, and development of side resistance.

The post-grouting technique for the bored pile construction can make the cement paste penetrate, fill and compact under the high pressure, and produce the physical and chemical consolidation with the settled materials, clay skin, and the soil body around the pile and on the tip of pile, increasing the side resistance and tip resistance, and further increasing the capacity of the single pile.

The developing degree of side resistance is well corresponding to the relative displacement between pile and soil.