The orthogonal test L9(34) program is designed by taking slenderness ratio of piles l/d

ratio of pile spacing to pile diameter s/d

thickness of grouting body h as factors and the ultimate load-bearing capacity of single pile Qu and settlement of pile top under a load Sp as inspection parameters. The finite element method is used to analyze load-bearing behavior of single pile with post grouting at pile tip

and then order of factors and effect rules are got. The results show that the ratio of pile spacing to pile diameter s/d is the most important factor for bearing capacity or settlement of pile. When the s/d is larger

the effect of post grouting at pile tip on the increase in bearing capacity and the reduction in settlement of pile is more obvious. The post-grouting at pile tip can increase pile tip resistance and change the bearing behavior of pile gradually from the friction pile into the end bearing friction pile

friction end bearing pile

or end bearing pile.