超大断面小净距隧道工法适用性研究

超大断面小净距隧道往往处于洞口段，具有地质条件差、工序多、干扰强等特点。施工中分部过多会影响工效、分部过少易导致失稳，所以合理的开挖工法至关重要。依托济南绕城高速连接线大岭隧道工程，采用数值分析、现场实测方法对半步CD法、CD法和双侧壁导坑法三种可能的开挖工法进行适用性比选研究。以拱顶沉降、夹岩水平位移、夹岩应力为指标对不同工法的施工力学行为进行分析，发现大岭隧道后行洞施工对先行洞产生影响，不同工法的影响程度排序：半步CD法>CD法>双侧壁导坑法。但半步CD法影响程度并未显著高于CD法和双侧壁导坑法，其增加量最大为12%，现场可采用半步CD法进行施工。最后钢架应力、位移等监测数据表明：半步CD法可以保证工程安全、缩短工期、降低成本，是三种工法中最适用的工法。半步CD法的使用产生了较好的经济效益和社会效益，可为类似地质条件下超大断面小净距隧道的设计和施工提供技术指导。

Applicability study on construction method of super-large section neighborhood tunnel

Neighborhood tunnel is often located at the entrance. When the section is super-large, it always has the characteristics of poor geological condition, many procedures and strong interference. If excavation segments are too many which affect the work efficiency, otherwise, the tunnel is easy to lose stability, so the reasonable excavation method is important to choose. Relying on Daling tunnel of Ji′nan expressway connecting line, methods of numerical analysis and field monitoring have been used to study on the applicability of half-step CD method, CD method and double side-heading method. Seveal indexs have been choosen to analyze the mechanical behaviour, such as vault settlement, horizontal displacement and stress of shared rock. The second tunnel construction has an impact on the first one, for the different construction method, influence sort from large to small is half-step CD>CD>double side-heading method. The impact of half-step CD method isn′t significantly higher than CD and double side-heading method and the maximum amount is 12%. Therefore, half-step CD method can be adopted. Monitoring data of stress and displacement of steel frame show that half-step CD method can ensure the project safety, short the construction period and reduce costs, which is the most suitable method. By using half-step CD method, Daling tunnel produce good economic and social benefits, which can guide the tunnel′s design and construction under similar geological conditions.