ABSTRACT
This paper presents the technical challenges and innovative solutions encountered during the undercrossing of the viaduct of Metro Line 1 by the new Metro Line 2 in Lima, Peru. This involved TBM tunnelling in inner-city conditions with low overburden and special ground conditions characterized by compact conglomerate of Lima, exhibiting unique ground behavior during tunnelling. The experience gained from this project highlights the TBM parameters, monitoring measures, and technical solutions implemented to minimize risks. Specifically, systematic grouting measures below the foundation of the viaduct were carried out using synthetic resin to improve the stability of the tunnelling area and to reduce tunnel-induced ground overbreak and settlements. The approach to the materials used and the specific challenges faced in this project underscore the importance of tailored solutions in complex urban environments. Lessons learned from this project offer valuable insights for future tunnelling projects in similar conditions, emphasizing the critical balance between engineering solutions and risk mitigation strategies.
