Abstract:

The tunnel between Terminal 3 and Terminal 2 of Beijing Capital International Airport is a large crosssection singlestory doublearch tunnel with shallow cover. The tunnel, which crosses underneath a runway of the airport, is constructed by means of 10pilot sequential excavation method under the protection of long pipe roof. In the paper, the ground deformation caused by the tunnel construction is analyzed. Conclusions drawn are as follows: 1) The average of the maximum ground surface settlement caused by the tunnel construction is 9.28 mm, and the ground deformation has been brought under effective control, which shows that the application of the long pipe roof to protect the construction of the shallow tunnel is feasible; 2) The average of the adjustment coefficient obtained from the deformation fitting of three crosssections is 0.951, and the ground surface deformation is consistent with the Peck formula; 3) The average of the K value obtained from the deformation fitting is 1.903, which is 3~6 times the common value in Beijing; the pipe roof can barrier and diffuse the ground deformation caused by the construction of the tunnel; 4) The average of the Vl value obtained from the deformation fitting is 0.201%, which is slightly smaller than the common value in Beijing. 

Key words: tunnel, tunneling across underneath existing airport runway, pipe roof method, ground surface deformation