Comparative study on ground loss ratio due to shield tunnel with different diameters

The ground loss ratio is one of the main factors causing ground surface settlements. The measured data of the maximum ground settlement from some areas of China are collected. The ground loss ratios are obtained through back analysis of Peck formulas. The distribution and influence factors of the ground loss ratio due to large- and small-diameter shield tunnels are studied, respectively. The results show that: (1) About 93.19% of the ground loss ratio caused by small-diameter shield tunnel ranges from 0% to 2.0%, while about 70% of the ground loss ratio due to large-diameter (D>10 m) shield tunnel is 0 %~0.50%. The ground loss ratio owing to large-diameter shield tunnel is smaller, and the distribution is more concentrated compared with that of the small-diameter shield tunnel. (2) The ground loss ratio induced by small-diameter shield tunnel decreases as the soil conditions get better, while the ground loss ratio induced by large-diameter shield tunnel decreases with the decrease of permeability coefficient. (3) There is a certain correlation between the maximum ground settlement and the ground loss ratio, and the control of ground loss ratio resulting from small-diameter shield tunnel in soft soils is the most difficult. (4) The ground loss ratio has no obvious connection with the ratio of cover depth to diameter. (5) The ground loss ratio induced by small-diameter shield tunnel decreases with the increase of the cohesion, internal friction angle and modulus of elasticity. The results can provide scientific references for the prediction and control of ground settlement induced by similar tunnel construction in the future.