砂卵石层盾构开挖面失稳分析及双参数掘进控制

Analysis of Shield Excavation Face Failure and Tunneling Control with Two Parameters in Sandy Cobble Strata

摘要:

为探究砂卵石层盾构施工的开挖面失稳过程和支护力设定方法，针对成都地铁盾构掘进施工超挖失稳实例，开展了三维工程离散元（EDEM）分析，对不同支护力分布形式的极限支护力和开挖面稳定性进行分析。进而结合盾构施工超挖失稳区段的掘进参数，考虑盾构机整体机械性能配置，提出了开挖面稳定性双参数控制建议值。结果表明，开挖面失稳位置与支护力分布形式有关，开挖面处于极限状态时，盾构上方0.75 D（D为隧道直径）范围内产生土拱效应，当支护力逐渐减小至0.1 P0（P0为初始静止状态支护力）时，失稳区发展到地面；盾构掘进时应保持土仓适当欠压，并降低刀盘转速，为可能遇到的大粒径漂石和土仓压力控制预留足够的富余扭矩。

关键词:盾构隧道施工;开挖面稳定;极限支护力;刀盘扭矩;土仓压力

Abstract:

To explore the failure process of excavation face and setting of support force during shield tunneling， a three-dimensional engineering discrete element method（EDEM） analysis is conducted for the excavation face failure case in sandy cobble strata of Chengdu Metro. The limit support pressure and excavation face stability are analyzed under the conditions of different support force distributions. Based on the tunneling data observed in the excavation face failure case， the suggested values of two parameters during shield tunneling is proposed for stability of excavation face considering the overall mechanical performance of shield machine. The results show that the failure position of the excavation face is related to the support force distribution. The soil arching effect occurs within 0.75 D above the shield as the excavation face is in the limit state. The failure zone gradually develops to ground surface as the support force decreases to 0.1 P₀. The chamber pressure should be kept less than the static earth pressure with a low rotation speed of cutter head during tunneling， which is supposed to reserve enough cutter head torque for possible large size boulders and chamber pressure control.

Key words:shield tunneling construction;excavation face stability;limit support force;cutter head torque;chamber pressure