Author: Robbins

Continuous Conveyor Design in EPB TBM Applications

While continuous conveyors have become the muck removal system of choice in long, hard rock TBM tunnels, they have gained acceptance in soft ground tunnels only recently. Soft ground, EPB TBM-driven tunnels provide a challenging environment for continuous conveyors due to the variety of materials present. The design of both horizontal and vertical soft ground conveyors will vary depending on the types of excavated material, amount of water present, and other factors. This paper will address the challenges of effective conveyance in different ground materials by analyzing conveyor performance in several recent EPB TBM projects.

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Urban EPB Tunneling in Limited Space: A Case Study of the San Francisco Central Subway Project

The San Francisco Central Subway project is a challenging modern example of urban tunneling in limited space conditions. Two 6.3 m diameter Earth Pressure Balance Machines (EPBs) are excavating parallel 2.5 km long tunnels under low cover and in mixed ground conditions. The small launch site situated between an interstate and an off-ramp, highly curved tunnel alignment, and geology are particular challenges. These elements required customized tunnel and machine design, from TBM shipment and assembly, to launch and excavation.

This paper discusses the project challenges and solutions at the Central Subway project, with a focus on TBM and continuous conveyor logistics. Requirements of the project include explosion-proof electrical components, laser-guided survey, rubber-tired supply vehicles, and machine and back-up solutions for steep inclines and tight curves.

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