<p>On the basis of the complex variable method, the generalized series expansion (GSE) method for a circular shallow-buried segmental tunnel (CSST) in an elastic half-space is developed, whereby a complex variable solution of semi-analytical nature is obtained for the CSST in this study. In this study, complex potentials determining the solution of the surrounding medium of the tunnel are represented by generalized series. Generalized series of complex potentials consist of different orders of influence functions. The influence function of each order consists of two parts, i.e., singular and regular parts. Each order influence function of the surrounding medium satisfies the traction-free condition along the surface of the elastic half-space. The singular part of the influence function is one term of the complex potentials for a circular cavity in an elastic full-space, which is singular in the lower half-space occupied by the elastic half-space. The regular part of the influence function is analytic in the lower half-space and is determined by Cauchy’s integral theorem. In this study, the joint linking the segments of the lining is simplified as an effective narrow open cylindrical shell, and segments and joints as a whole, thus, form an effective cylindrical shell (ECS). Based on the thin shell theory for the ECS lining and corresponding series-form constitutive relation, equilibrium equations for the Fourier displacement components of the ECS lining are established. Using the surrounding-medium-lining (surrounding–lining) continuity condition, representations of the generalized series for the complex potentials of the surrounding medium and Fourier space equilibrium equations for the ECS lining, linear equations for potential coefficients of the surrounding medium and Fourier displacement components of the lining are developed. With the semi-analytical solution for the CSST, some numerical results for the responses of the CSST to external loads are presented.</p>