Abstract:

Excavation face failure and ground surface subsidence occurred at shield stopping section in expansive soil during the construction of Slender West Lake Tunnel. As a result, the expansion test and disintegration test are carried out. The main cause of the excavation face failure and ground surface subsidence, continuous permeation of slurry, is analyzed by site monitoring data and numerical simulation results. The excavation face failure can be divided into 4 phases, i. e. slurry permeating, soil expanding and disintegrating in front of excavation face, soil collapse above excavation face and ground surface subsidence. A series of countermeasures, such as shield boring parameter control, shield stop frequently and transiently, slurry support pressure increasing and slurry improving, are proposed and used. The good effect is achieved.

Key words: Slender West Lake Tunnel in Yangzhou, slurry shield, expansive clay, shield stop, excavation face failure