Abstract:

The four forepoling schemes such as horizontal drilling jet-grouting peg, full face deep boring grouting, long pipe roof grouting, space between-reduced little tremie grouting with constructing temporary invert, which were possibly adopted to the tunnel crossing river and bridge on line 5 of Beijing metro, were analyzed initially by using engineering experience. The comparison shows that the scheme of space between-reduced little tremie grouting has superiority in construction cost as well as rate of tunnelling and construction impact. Then, the scheme of long pipe roof grouting as well as the scheme of space between-reduced little tremie grouting were evaluated farther and compared by using three-dimensional numerical simulation. The numerical simulation results show that the impact on the bridge abutments, bridge piers and river bottom stratum produced in the scheme of long pipe roof grouting and the scheme of space between-reduced little tremie grouting respectively is equivalent in the condition of taking no account of stratum advance disturbance caused by the construction of long pipe roof. Therefore, the scheme of space between-reduced little tremie grouting will exceed the scheme of long pipe roof grouting in the condition of taking account of stratum advance disturbance caused by the construction of long pipe roof. The long pipe roofs as well as little tremies and foot-locking little tremies bear smaller bending moment. The foot-locking little tremies and little tremies belonging to tunnel crown will bear the axial pressure; little tremies belonging to tunnel side will bear both axial pressure and axial tensile force, while long pipe roofs will suffer mostly axial tensile force.

Key words: shallow tunnel, scheme optimization, ground displacement control, engineering experience, numerical simulation