Current theoretical studies on ground settlement induced by small curvature shield excavation generally consider the foundation as linear elastic bodies

neglecting the rheological behavior of soil. Therefore

the time-dependent settlement changes of shield excavation along curved path cannot be accurately predicted. A mechanical model for small curvature tunneling in a Boltzmann viscoelastic foundation was established. Time domain parameters of the viscoelastic ground were obtained through Laplace transforms of the Poisson’s ratio and shear modulus for the linear elastic ground parameters. Then

the solutions for ground loss and Mindlin displacement were converted by positive and inverse Laplace transforms. During small curvature shield construction in the viscoelastic ground

a settlement solution was derived that accounts for the combined effects of over-excavated ground loss

shield tail ground loss

cutterhead face thrust imbalance

shield shell friction imbalance and slurry pressure at the shield tail. Finally

field measurements and three-dimensional numerical simulation results are compared with the analytical solution to verify its relative accuracy. In addition

the parameters of tunnel curvature radius

shield cutterhead face radius and viscoelastic ground shear modulus ratio are analyzed. The analysis results show that the transverse surface settlement inside and outside the small curvature tunnel is asymmetrically distributed

with the peak settlement shifting inward. The settlement trough curve shifts downward and the settlement volume increases with time. A smaller tunnel curvature radius has a more significant effect on ground settlement compared to a larger tunnel radius curvature with equal changes. Reduction in tunnel curvature radius and viscoelastic ground shear modulus ratio

along with growth in cutterhead face radius and over-excavated value

result in the increase in transverse surface settlement at the shield tail

as well as the increase in uplift and settlement of the longitudinal surface both before and behind the cutterhead face.