Analysis of the Support Effect of Micro Steel Pipe Pile-Anchor Bolt at Tunnel Portal Slope Based on the Incremental Method
The combined support system of micro steel pipe pile and anchor bolt,due to its advantages such as con-venient construction,simple structure,and flexible layout,is widely used in landslide remediation and foundation pit protection projects,but its application in tunnel portal slopes is less common.Based on the Georgia No.1 Tunnel project,the incremental method is used to conduct a numerical simulation study of the support effect of the micro steel pipe pile-anchor bolt system at tunnel portal slopes,and the simulation results are analyzed in conjunction with field monitoring data.The research results show that the incremental method considering the construction pro-cess is more reasonable for simulating the micro steel pipe pile-anchor bolt support system.After the pile breaking construction,the maximum displacement of the slope is 10.20 mm,the maximum axial force of the anchor bolt is 339.42 kN,which is less than the design axial force of the anchor bolt of 420.14 kN.The maximum lateral displace-ment of the selected characteristic pile is 9.90 mm,and the maximum bending moment is 31.26 kN·m,which is lower than the design bending moment value of 84.80 kN·m.The actual monitoring results of the vertical displacement of the slope and the numerical simulation results both show a"V"shaped distribution and the data are consistent.The crown settlements of the left and right tunnels are 11.11 mm and 8.01 mm,respectively,and the horizontal displace-ments are 2.33 mm and 1.30 mm,respectively.The micro steel pipe pile-anchor bolt support system has been suc-cessfully applied to the Georgia No.1 Tunnel project,ensuring the construction safety of the tunnel portal section.
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