Abstract: The polymer grouting bag pile is a new type of foundation reinforcement technology developed for the foundation reinforcement of existing buildings. In order to explore the applicability of polymer grouting bag pile to the foundation reinforcement of existing buildings, we investigated into the construction technology, law of pile formation and reinforcement effect of polymer grouting bag pile through the experiment of grouting pile in soil with different densities and layering conditions. The experimental results demonstrated that polymer bag pile has obvious effect on compacting soil mass. After piling, the pile diameter can reach 2D-3D (D represents the diameter of drilling hole). In the presence of the same grouting quantity, the pile diameter shrinked with the increase of soil density, while the pile density expanded with the increase of soil density. Meanwhile, polymer grouting bag pile can also pass through the hard interlayer to form a gourd-shaped body and plays a better role in strengthening the soft soil foundation. The results of field light dynamic penetration test showed that the hammer stroke of light dynamic penetration test increased by 2-3 times in the soil reinforced by polymer grouting pile, an improvement of 30%-50%. Therefore, polymer grouting bag pile has good reinforcement effect and is feasible for strengthening weak foundation.

Key words: foundation reinforcement, polymer bag grouting pile, model test, construction technology, laws of pile-forming, hard interlayer