Abstract: Shield tunneling in strongly-e soil should be improved. The three soil conditioning methods, i.e., moisture content optimization, dispersing agent injection, and foaming agent injection, are adopted to improve the strongly-weathered granite in the Liuxiandong station-Baimang station of the Shenzhen metro line 13 using a self-developed soil-genus interface adhesion tester. The conclusions drawn are as follows: (1) The optimization of moisture content can effectively reduce the normal and the tangential adhesions of the soil; whereas, the dispersant and foaming agents can only improve the tangential adhesion while increasing normal adhesion and the dispersing agent can increase the normal adhesion with a larger amplitude. (2) The foaming agent has a better improvement effect on the tunneling speed, thrust, torque, and tunneling specific energy of the shield. When compared with the first chamber opening, the second chamber opening shows an improvement of up to 23% in all tunneling parameters. (3) The foaming agent cannot completely prevent the phenomenon of mud cake on the cutterhead. It is recommended to optimize the soil moisture content while adopting the foaming agent to minimize the risk of mud cake formation on the cutterhead.

Key words: shield tunnel, granite stratum, soil conditioning, interfacial adhesion, moisture content optimization, foaming agent, dispersing agent