ABSTRACT
The Regional Connector Transit Corridor (RCTC) Project is a $1.9B design-build project currently under construction by the Los Angeles County Metropolitan Transportation Authority (Metro). The light rail subway project comprises major underground elements, including Metro’s first mined rail crossover cavern, which is horseshoe shaped, 56-ft (17-m) wide by 34-ft (10.4-m) high and nearly 300-ft (91.4-m) long. Located in one of the most active seismic regions of the world, the cavern structure underwent comprehensive seismic design to comply with rigorous seismic design criteria and other design requirements. The construction of the cavern structure was substantially completed in 2020. For the seismic design of the cavern structure, a fully-coupled dynamic time history analysis was performed using FLAC models. During the course of the dynamic analysis, the influence of the initial lining on the dynamic performance of the final lining was particularly evaluated. The numerical model was also used for a sensitivity analysis to assess the impact of different bonding conditions between the initial and final linings during a seismic event. The analysis incorporated stiffness, material properties, inertial effects, and dynamic behavior of the initial lining and the interface between initial and final linings. The analysis and results are discussed in this paper.
