Abstract:

In order to solve the problems during tunnel construction in the recent backfill strata and foundation treatment of open-cut tunnel in the trench terrain, research work is carried out on Zaoyang Tunnel in Wushan County. Firstly, schemes of mining excavation and open-cut tunnel are introduced in detail and compared comprehensively. And then the pile-plank structure composed of rotary drilling borehole cast-in-place end-bearing piles and reinforce foundation board is used in open-cut tunnel foundation treatment in the trench terrain. Finally, in view of the heavy backfill soil load on the top of open-cut tunnel lining and the municipal road load across the top, the design and calculation of open-cut tunnel lining structure are carried out, and the strict requirements of open-cut tunnel backfilling materials and backfilling technology are carried out. The results show that: (1) The scheme of open-cut tunnel in the recent backfill strata has the advantages of low engineering difficulty, low risk of construction safety, low engineering cost and controllable construction period. (2) The pile-plank structure can adapt to the complex terrain, which is safe and efficient and can better solve the problems of scant foundation bearing capacity and the settlement of open-cut tunnel. (3) It is important to select suitable backfill materials and reasonable filling method for the protection of lining structure.

Key words: recent backfill, open-cut tunnel, subgrade settlement, foundation treatment, pile-plank structure, loadstructure method