Purpose <p>The octal-shaped tunnel (OST) is an innovative technique in tunneling engineering. Circular, oval, horseshoe and rectangular-shaped tunnels are available in the world. For this reason, this research proposes modified analytical formulations of OST for static loading, finite element formulae of OST under static and seismic loadings, and idealized construction techniques of OST.</p> Methods <p>Modified analytical formulations of OST are developed to consider the image sink technique. The OST is acted as a 4-nodded line element to connect each node with a linear spring to derive the finite element formulations under the static and seismic loadings. Five idealized successive construction stages of the OST are considered in this research. In addition, formulae of geotextile-wrapped steel bar (GWSB) are proposed based on the general consideration. Soil medium is considered to be a homogenous, elastic, isotropic, and incompressible to derive the analytical and finite element formulations.</p> Results <p>The verification results of analytical and finite element formulae are found to be 2.94% and 1.52%, respectively, which may indicate a good accuracy with verification. The settlements of sand for circular and rectangular tunnels are 3.8% and 5.8% higher than the OST under static and seismic loadings based on the Plaxis 3D analysis. Also, the maximum vertical displacements of the OST and OST with GWSB are the same.</p> Conclusion <p>Therefore, the proposed construction technique of the OST may help engineers to make a full-scale model in the field to find accurate responses under seismic excitations. Also, there is a scope to enhance this research in future to incorporate heterogeneity, incompressibility, etc. impact of soil on the OST.</p>