Abstract:

The failure of tunnel face stability often occurs during tunneling in fullyweathered red sandstone. Hence, a case study is conducted on the Yangcheng tunnel of HaolebaojiJi′an railway. Then a systematic study on the deformation characteristics and control measures of tunnel face in fullyweathered red sandstone stratum is conducted using various research methods such as field investigation, laboratory test, and numerical simulation. Research results reveal the following: (1) The extrusion displacement of tunnel face is mainly concentrated in the position of face height of 3~10 m, and the maximum extrusion displacement of tunnel face appears at the junction of upper and middle benches. (2) The crown settlement mainly occurs at about one time of the tunnel diameter in front of the excavated section and the tunnel face, which accounts for more than 40% in total deformation (with a maximum reaching 78.33%). (3) The change in the core soil extrusion curve in front of the tunnel face decreases rapidly first and then becomes slowly, which can be roughly divided into strong influence, weak influence, and no influence zones. The range of influence is 5.8~19.2 m. (4) The extrusion deformation of the tunnel face of Yangcheng tunnel can be effectively controlled by adopting advance horizontal jet grouting pile and threebench reserved core soil method. The two proposed methods can be applied under the premise of dewatering.

Key words:

railway tunnel, fullyweathered red sandstone, tunnel face deformation, advance horizontal jet grouting pile, threebench reserved core soil, dewatering