管幕冻结法浅埋大断面隧道开挖方案对衬砌性态及地层位移的影响

Impact of Excavation Procedures of Shallow Large Cross-section Tunnel with Pipe-roofing and Frozen Soil on Tunnel Behavior and Ground Movement

经验表明,在软土、浅埋大断面隧道开挖方案中,加固方式对衬砌结构受力、隧道收敛变形和地层位移影响显著。港珠澳大桥珠海连接线拱北隧道具有隧道埋深浅、结构断面尺寸大、地质条件差、地理位置政治敏感性强等特点。以该隧道为背景,利用数值模拟方法,分析大直径钢管管幕冻结法施工和隧道开挖方案对衬砌结构受力和地层变形的影响。经分析发现:不同开挖方案对衬砌受力、变形和地层位移的影响显著;在分台阶开挖过程中,台阶越小,引起的衬砌受力、隧道收敛变形和地层位移越小;管幕冻结对改善衬砌受力和地层位移效果显著,根据管幕冻土受力特性对其关键受力部位提出建议。

The tunnel excavation using mining method affects the tunnel behavior and ground movement significantly. Gongbei connection line of Hong Kong-Zhuhai-Macao Bridge is a shallow large cross-section tunnel,with poor soil quality and high political sensitivity.In the paper,four potential excavation procedures are studied for the tunnel using FEM.The numerical results indicate that the excavation procedure has significant effect on the lining force,tunnel convergence and ground movement.The ground improvement using pipe roofing and frozen soil supporting is also investigated.The effect of ground improvement is then checked in terms of the tunnel lining force and tunnel convergence.It is found that the ground improvement can reduce the lining force and ground movement significantly.