Study on the Pullout Resistance of Hollow GFRP Reinforced Soil Nails
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摘要: 中空GFRP筋土钉是一种空心厚壁土钉，具有质量轻、易切割、耐腐蚀等优点。目前，对中空GFRP筋土钉的研究相对较少，对其抗拔性能和抗拔机理尚不清楚。依托北京地铁12号线北岗子站基坑工程，对中空GFRP筋土钉进行了现场抗拔试验，并采用FLAC3D数值模拟探究了不同拉拔力下中空GFRP筋土钉应力和位移沿钉长的分布规律，分析了不同内径和长度对应力分布和抗拔力的影响，对中空GFRP筋土钉的抗拔机理进行了分析。研究结果表明，拉拔过程中土钉的位移和轴力沿钉长呈指数衰减，剪应力在距钉头1.5 m处达到峰值，在距离钉头3.5 m处降至零；增大内径使土钉轴力沿钉长衰减更快，同时可提高其抗拔承载力，建议外径为32 mm的中空GFRP土钉内径取为15 mm；增加土钉长度不仅可以在一定范围内提高其抗拔力，还可使土钉轴力分布更均匀；中空GFRP筋土钉的破坏过程可分为弹性、塑性和破坏三个阶段，其破坏形式表现为拔出。Abstract: 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.
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表 1 材料参数表
名称 重度γ/（kN ·m−3） 弹性模量
E/MPa泊松比ν 黏聚力c/kPa 土体 18.4 12 0.30 19 GFRP筋 20.0 46000 0.28 水泥砂浆 22.0 3000 0.25 
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表 2 接触面参数表
接触类别 法向刚度Kn/MPa 切向刚度Ks/MPa 黏聚力/kPa 内摩擦角
/(°)GFRP土钉
与水泥浆5.75e12 5.75e12 1760 26 水泥砂浆与土体 3.75e11 3.75e11 23.8 18
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