Factors influencing the ground loss due to tunnels driven by EPB shield

The ground loss and therefore the prediction of ground surface settlement during shield tunnelling in urban area is of utmost importance to ensure the safety of underground utilities or adjacent buildings. In this paper a generalized correlation between the surface settlement and some ground toss control measures is presented. Monitoring data on ground surface subsidence and field records of mucking, back-fill grouting and chamber pressure of the EPB shields acquired from the construction of Taipei's rapid transit tunnels were analyzed. It was found in this study that the major factors influencing the surface subsidence may include the quantity of grouttake, the volume of the tail void of the shield, the shield chamber pressure, and the depth of tunnel. A correlation between the ground loss ratio and the major factors were formulated through statistical models.