Research On The Bearing Behavior Of Post-grouting Pile

The post-grouting pile is a new technology created in recent years, which can effectively improve the mechanical properties of the soil around piles by post-grouting, increase the bearing capacity of the pile, reduce the pile settlement, eliminate the inherent defects caused by shaft mud cake and bottom sediment and is widely used in engineering field. However, this technology is currently in the state summarizing engineering experience and exploring the rule of pile bearing capacity, have no systematic understanding of factors influencing the bearing capacity of post-grouting pile, lacks of research on the rule of bearing capacity of post-grouting pile impacted by factors.This paper takes the method of orthogonal analysis, which takes design parameters of post-grouting piles as factors to design the orthogonal test program and calculates the pile model by the finite element method to analyze the calculation result, to find out the importance order of the bearing capacity and settlement of piles, which influenced by factors, and the rule of pile bearing behavior with variation of factors. What’s more, the finite element calculation are performed on single pile and group piles under the same condition, contrast and analyze the calculation result with no grouting and grouting, to conclude the rule of pile bearing capacity under the vertical load influenced by post grouting.According to the result of orthogonal analysis, this paper can conclude that radio between pile spacing and pile diameter s/d of post-grouting pile is the most important factor of the pile bearing capacity, and post grouting will enhance the bearing capacity of single pile apparently when the s/d is large; the post-grouting at the pile tip decreased the pressure of soil at the pile tip, reduced the settlement of pile, increase the proportion of the pile tip resistance inside the pile bearing capacity and enhance the ultimate bearing capacity of pile foundation; the post-grouting at pile bottom could change the load-bearing behavior of pile gradually from the friction pile into the end bearing friction pile, friction end bearing pile, or end bearing pile; for the post-grouting group piles, radio between pile spacing and pile diameter s/d have the most effective influence, and the pile settlement apparently enhance with the s/d is increasingly enlarged. The large range of post-grouting will decrease the nonuniform settlement of pile foundation and the trend of dished settlement; the overall post-grouting at the pile bottom will increase the resistance at the pile tip and aggravate the nonuniform distribution of resistance of group piles tip; with the grouting field is increasingly large, the distribution of subsoil’s reaction beneath the cushion cap will be more uniform, the difference of pile tip resistance between outside soil and inside soil will decrease and achieve the minimum when the pile foundation is overall post-grouting.