Abstract: At present, theoretical analyses on double-arch tunnel construction effects have rarely considered the construction impacts induced by the middle guide tunnel, despite its prevalence in practical designs. During construction, the middle guide tunnel is excavated first, sharing its lining boundary with adjacent left (tunnel 1) and right (tunnel 2) caverns, while requiring backfilling and reconstruction of the central diaphragm wall. Based on complex variable function theory and the Schwarz alternating method, this study proposes a calculation approach for stress and deformation in lining-surrounding rock systems of double-arch tunnels incorporating middle guide tunnel effects. For the shared lining boundary between the middle guide tunnel and lateral caverns, the Cauchy integral method transforms boundary integral conditions into the difference between complete single-cavity integrals and shared boundary integrals. This aligns with the Schwarz alternating method’s concept of “additional surface forces” generated during three-cavity interaction analysis. Validation against monitoring data and numerical simulations from the Suzhou Qizi Mountain double-arch tunnel project confirms the feasibility of this complex function approach. Parametric sensitivity analyses were conducted for Poisson’s ratio, surrounding rock elastic modulus, middle guide tunnel aspect ratio, and double-arch symmetry. Key findings include: elastic modulus variations exhibit consistent impacts on Tunnel 1 and 2 lining displacements-higher modulus correlates with reduced total displacement at equivalent angles, showing “W”-shaped profiles with inflection points at arch springings. Increased middle guide tunnel aspect ratio (toward “tall-narrow” geometry) elevates maximum principal stresses in both surrounding rock and lining. Symmetrical enlargement/reduction of adjacent cavern sizes while maintaining middle guide tunnel dimensions amplifies/reduces original cavern lining displacements, particularly in shared lining regions.

Key words: continuous arch tunnel, middle guideway, Schwarz alternate method, complex variable function, stress field, displacement field