To evaluate the changing degree of single pile vertical bearing behavior resulted by defect piles such as stem shrinkage pile

stem enlargement pile and broken pile which are developed in construction process

field model tests were used to analyze single defect piles. And measurements of its ultimate bearing behavior were carried out by conducting vertical static loaded tests of test piles with and without defects. Compared with normal piles

the influences of defects mentioned above on bearing behavior of piles were studied. Conclusions are drawn based on the designing scheme of test piles in the paper through comparative analyses of the load-settlement curves of normal piles and defect piles. Compared with the vertical ultimate load capacity of single normal pile

it reduces by less than 15 percent due to defects in single pile such as stem shrinkage pile or a pile with mud cake around. The steep drop point is not so clear in the load-settlement curve of single stem shrinkage pile

the top settlement of which increases more gradually than normal pile. The occurrence of inflection point in load-settlement curves of broken piles is determined by the distance of broken defect from ground surface.