Sub-river Shield Tunnel for Chongqing Urban Drainage Works is one of the state highlight environmental protection projects and the greatest shield tunnel in the Yangtze River. This sub-river tunnel is constructed with slurry shield machine. Because the main agent structure will bear 0.6 MPa high hydraulic pressure during both construction and operation period

it is significant to study the effects of high hydraulic pressure on shield tunnel. Based on topographic

geological and hydrological conditions in tunnel site

in-situ tracking test for hydraulic pressure on main agent structure of shield tunnel were carried out in construction period to acquire the distribution regularities of external water pressure and provide important parameters for tunnelling control. Thus

profitable references are provided for similar project construction.