Abstract:

Sujiachuan tunnel on BaojiLanzhou railway is a large crosssection tunnel located in Tertiary sandy loess. The crown settlement under different distances between the tunnel face and the invert closing position is analyzed by means of “midas” program, the rule of the deformation of large crosssection loess tunnels in the process of construction is expounded and the appropriate distance between the tunnel face and the invert closing position is determined to be 35 m. The tunnel is constructed by top heading and twobench method, with temporary inverts installed, and the excavation cycle rate is controlled at 0.6 m in the top heading and 1.2 m in the benches. Forepoling and arch foot locking bolts are installed for the tunnel. In the end, good deformation control effect has been achieved, with the maximum settlement being control from 50 mm to 160 mm. Furthermore, the rule of the convergence of tunnels with different crosssections is analyzed and it is concluded that the value from 120 mm to 160 mm can be taken as the deformation allowance of large crosssection loess tunnels.

Key words: large crosssection loess tunnel, top heading and twobench method, deformation control, distance between tunnel face and invert closing position, deformation allowance