下穿公路连拱隧道双层管棚预加固作用数值分析

以土江冲隧道为背景，采用FLAC^30软件对双层管棚在下穿公路连拱隧道施工中的加固作用进行分析，数值计算中以梁单元模拟管棚钢管，适当提高管棚加固区围岩参数模拟管棚注浆．计算结果表明：隧道掌子面附近管棚的变形和受力较大，通过设置管棚和不设置管棚两种计算结果与现场测试数据之间的相互比较，对双层管棚在既有公路下连拱隧道施工中的预加固作用进行了评价．比较结果表明：管棚的主要作用是抑制地层位移和主洞初期支护变形，采用双层管棚可使隧道开挖引起的地表沉降减小40％-50％．

Numerical analysis of pre-reinforcement action about double-layer pipe roof in multi-arch tunnel under the existing highway

Tujiangchong Tunnel was as the background and the pre-reinforcement action of double-layer pipe roof in the multi-arch tunnel construction under the existing highway was simulated by FLAC3D.The beam element was adopted to simulate the steel pipes and jet-grouting was simulated by appropriately enhancing the property parameter of surrounding rock reinforced by pipe roof.The results show that the deformation and the force of pipe roof nearby the excavation face were larger.Based on the comparison with the field-test values and the calculation results of pipe roof reinforcement and without pipe roof reinforcement,the pre-reinforcement action of double-layer pipe roof in the multi-arch tunnel construction under the existing highway was evaluated.The comparison results show that the main action of pipe roof was restraining ground movement and the deformation of primary lining,and the potential ground surface settlement caused by tunnel excavation could reduce 40%~50% with the double-layer pipe roof pre-reinforcement.