Two-Dimensional Numerical Analysis of the Effects of Different Construction Methodologies on Tunnel Behavior

Resumo

Abstract: The growth of urban populations necessitates the construction of robust infrastructure, including highways, public transportation systems, sanitation networks, and housing. Consequently, underground space utilization becomes pivotal, prompting the construction of tunnels, access shafts, and galleries. However, such construction encounters challenges due to the unpredictable geotechnical and geological characteristics of the excavation site, especially when sensitive structures are nearby. This study examines the impact of various tunnel construction methodologies on earth mass behavior, with a particular focus on deformations, surface displacements, and forces exerted on linings. To this end, numerical simulations were conducted utilizing ABAQUS finite element software under plane strain conditions. These simulations were designed to simulate conditions akin to a tunnel project in Florianópolis. The numerical model encompasses four layers of soils and rocks, spanning approximately 70 meters in depth and 190 meters in width. The tunnels, with an excavated area of 161.29 m², are situated 20 meters below ground and are equipped with primary and secondary linings. The soils/rock and linings are modeled using Mohr-Coulomb and linear elastic failure criteria, respectively. The soil domain was modeled with CPE4 elements, while the linings domain employed CPE4I elements. The study initially examines the convergence and confinement curves to incorporate the three-dimensional effects of construction, considering the degree of mass relaxation during lining application. The construction sequences for single and twin tunnels entail full-section excavation, subsequent placement of the definitive crown and inverted arch, and side drift associated with half-section and inverted arch. The results discuss and highlight earth mass deformation patterns, critical areas during construction, surface displacement basins, and forces exerted on linings at various excavation phases. The effectiveness of various construction methodologies in reducing deformations and enhancing project safety is evaluated. The conclusions drawn from the numerical analyses offer valuable insights for tunnel project professionals, facilitating the development of more efficient and safer construction practices.