为解决宁波地铁7号线盾构穿越淤泥地层中预应力钢筋混凝土管桩群施工难题，采用室内模拟试验方法，开展盾构在不加固地层和MJS加固地层2种工况下直接切削管桩的模拟试验，对比分析盾构在2种工况下直接切削管桩的效果、刀具磨损及掘进参数。试验表明： 1)在不加固的淤泥地层中直接切削管桩容易发生位移，切削较困难，不利于掘进; 2)齿形中心鱼尾刀与软土贝壳撕裂刀分层布置能有效切削C50强度的管桩，且对切削预应力钢筋和管桩法兰接头的适应性良好; 3)采用MJS水泥土加固能有效固定管桩并提供支撑力，有利于刀具对管桩进行切削，可有效提高施工效率及降低施工风险; 4)刀盘转矩与刀具贯入度基本呈正相关性，合理设置掘进参数可减小刀盘阻力、降低转矩。建议在相似地层加固工况下切削混凝土管桩，推进速度宜控制在10 mm/min左右，刀盘转速为1.0~1.2 r/min，贯入度不宜超过10 mm/r，以兼顾掘进效率与平衡设备负荷。试验结果经工程应用验证良好，为施工现场配置盾构和选择掘进参数提供了有力的依据。
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.
