Abstract: Unlike conventional tunnel lining structures, the antecedence tunnel lining is subject to secondary disturbances from the later excavated tunnel excavation after the lining has been stabilized. The excavation impact of the later excavated tunnel on the surrounding rock pressure acting on the antecedence tunnel lining cannot be ignored. Relying on Yangjiazhai tunnel project, a calculation method for surrounding rock pressure that accounts for the influence of the second tunnel excavation has been developed. This method, in combination with on-site monitoring displacement data and utilizing the load-structure method for inverse analysis, proposes a means of determining the load acting on the antecedence tunnel lining. The field-measured values of the surrounding rock pressure behind the lining were used for comparison and verification. The study results have yielded important insights: 1) The impact of the second tunnel excavation on the first tunnel lining’s ability to withstand surrounding rock pressure is substantial, with the average increase in monitoring points reaching as high as 142%. 2) The pressure acting on the antecedence tunnel lining follows a distribution pattern of being lower at the waist of the arch and higher at the top and the shoulder, with the shoulder of the arch near the later excavated tunnel experiencing the greatest pressure. 3) The results of the surrounding rock loading obtained from the inverse analysis are more consistent with the field monitoring results, which argues for the soundness and practicality of the approach, and providing a reference basis for the structural design for the double-arch tunnel without middle drift.

Key words: load structure method, double-arch tunnel without middle drift, displacement inverse analysis, force on the lining