Innovative Hybrid EPB Tunnelling in Rio de Janeiro
The Line 4 South being constructed in Rio de Janeiro crosses complex geology that includes a long stretch of sand bounded by two stretches of hard, highly abrasive rock. These geological conditions, combined with the fact that the project is located in a distinct urban area, creates a demanding project scenario where special care needs to be taken. After carrying out an evaluation to determine whether to use Earth Pressure Balance or slurry technology, the design of a convertible EPB boring machine that can excavate both rock and soils was developed. This paper outlines the technical difficulties that the project presents and describes the decision-making process and the solutions adopted. A technical description of the different operation modes of this hybrid TBM and the conditioning process related to each of them is provided.