破碎岩体浅埋大跨公路隧道开挖方案对比研究

三车道高速公路隧道通常跨度较大、高跨比较小属于大跨扁平隧道。这种结构型式对围岩稳定和结构受力均产生不利影响，因此施工中有必要通过开挖方案比选确定合理的开挖方法。江苏省宁波-常州高速公路茅山东隧道为上下行分离式双向6车道浅埋大跨扁平隧道。对于破碎的Ⅳ级围岩，针对设计阶段拟采用CRD法和实际施工采用下断面左右分部台阶法的开挖方案在设计支护条件下的三维数值模拟，从理论上分析了下断面左右分部台阶法是可行的。与实际施工过程的监控量测结果进行对比分析，进一步证实了实际开挖方案的合理性。研究成果可以为同类工程的设计与施工提供理论参考。

Comparative study on tunneling scheme of shallow overburden and large-span highway tunnel in cracked rock mass

Expressway tunnel of three driveways is often large-span tunnel with oblate cross-section because excavation span is large and ratio of height to span is small. This structure shape could make a bad influence on stability of surrounding rock and stress distribution of support system, so it is necessary to determine a reasonable tunneling scheme by academic analysis. The east Mao Mountain tunnel on the Ning-Chang Expressway in Jiangsu province is designed as a separate tunnel with uplink and downlink both having three driveways respectively. It is a typical shallow, large-span and oblate tunnel. The three dimensional numerical simulation using the FLAC3D software is conducted in this paper to model different excavation schemes, including CRD method proposed in pre-designing and partial bench cut method adopted in practice. The support parameters used in these two numerical models are both accordant with the data in design. The results show that partial bench cut method is feasible. A comparison between numerical results and observation data in practice is also conducted in the paper, which is more approved that the actual tunneling scheme is reasonable. The results of this study are expected to provide academic reference to design and construction for the similar engineering.