Study on the Pullout Resistance of Hollow GFRP Reinforced Soil Nails

Hollow GFRP reinforced soil nail is a kind of hollow thick-walled soil nail, which has the advantages of light weight, easy cutting, and corrosion resistance. At present, there are relatively few studies on hollow GFRP soil nails, and their pullout resistance and pullout resistance mechanisms are still unclear. Relying on the foundation pit project of Beigangzi Station of Beijing Metro Line 12, the field pullout test of hollow GFRP reinforced soil nails was carried out, and numerical simulation in FLAC3D was used to investigate the distribution of stress and displacement along the nail length of hollow GFRP reinforced soil nails with different pullout force. The effects of different inner diameters and lengths on stress distribution and pullout resistance were analyzed, and finally, the pullout resistance mechanism of hollow GFRP reinforced soil nails was summarized. The results show that the displacement and axial force of soil nails in the process of pullout decay exponentially along the length of the nails. The shear stress peaks at 1.5 m from the nail head and decreases to zero at 3.5 m from the nail head; increasing the inner diameter makes the axial force of the soil nail decay faster along the nail length, and at the same time improves its pullout capacity. It is recommended that the inner diameter of the hollow GFRP soil nails with an outer diameter of 32 mm be taken as 15 mm; increasing the length of the soil nails not only improves the pullout capacity to a certain extent, but also makes the axial force of the nails more uniformly distributed; the destructive process of the hollow GFRP soil nails can be divided into the three stages of elasticity, plasticity, and damage, and the damage form is manifested as pullout.