关键词: 盾构, 预应力钢筋混凝土管桩试验, MJS加固地层, 贝壳撕裂刀, 刀具配置, 参数选择

Abstract: During shield tunneling in the silt stratum of the Ningbo metro line 7 in China, a group of prestressed reinforced concrete pipe piles were encountered. Direct cutting of the pipe piles by the shield was simulated under two strata conditions: unreinforced stratum and metro-jet-system (MJS)-reinforced stratum. After comparing the effects of direct cutting pipe piles, tool wear, and tunneling parameters under the two conditions, it was found that (1) direct cutting of pipe piles in an unreinforced silt stratum is difficult and prone to displacement, thus inhibiting the tunneling; (2) a layered arrangement of tooth-shaped center fish-tail cutters and soft-soil shell tearing cutters can effectively cut pipe piles of C50 strength, and is easily adaptable to the cutting of prestressed reinforcement and pipe pile flange joints; (3) MJS cement soil reinforcement can effectively fix the piles and provide support, facilitating the cutting of pipe piles by the tools and effectively improving the construction efficiency while reducing the construction risks; (4) the torque of the cutterhead is generally positively correlated with the tool penetration and can be reduced by reasonably setting the tunneling parameters to reduce the cutterhead resistance. Under similar stratum-reinforcement conditions, controlling the cutting speed of concrete pipe piles at around 10 mm/min, setting a cutterhead speed of 1.0－1.2 r/min, and maintaining the penetration at 10 mm/r or lower are recommended for balancing the tunneling efficiency and equipment load. The test results have been well verified in engineering applications, providing a strong basis for the configuration of shields and the selection of tunneling parameters on construction sites.

Key words: shield, cutting prestressed reinforced concrete pipe pile test, metro-jet-system ground reinforcement, shell-tearing cutter, cutter configuration, parameter selection