Abstract:

In order to study the feasibility and applicability of a new tunneling method in soft surrounding rock,i. e. the single-hole method without mid-wall,the comparative analysis is made on construction mechanical properties of the single-tunnel method without mid-wall and the traditional three-pilot drift method by means of numerical simulation based on the Pingyuan-WenshanHigh-speed Tujichong double-arch tunnel. Meanwhile, the feasibility and safety of the construction method are verified by the statistical analysis of the field monitoring results. The results show that: (1) In terms of deformation control, the two method meet the requirements of safe construction both, but the three-pilot drift method is slightly superior to the single-tunnel method without mid-wall. (2)In terms of the bearing performance of the supporting structure, the stress concentration phenomenon can be effectively reduced by the single-tunnel method without mid-wall for its less temporary support structure adopted and smooth structure. (3) In terms of the structural design, the construction difficulty of the single-tunnel method without mid-wall is small than that of three-pilot drift method due to mid-wall cancel. (4) In terms of the construction method, the construction space is enlarged and the construction organization efficiency is improved by adopting three-bench method to construct two single tunnels. (5) Considering the influence of construction mechanics and construction schedule, the the single-tunnel method without mid-wall has a good applicability which can provide reference for the design and construction of double-arch tunnels under similar stratum conditions in the future.

Key words: soft ground, multi-arch tunnel, three-pilot drift method, single-tunnel method without mid-wall, field monitoring