ABSTRACT
Earth pressure balance (EPB) tunnel boring machines (TBMs) are commonly used to build tunnels in soft ground and mixed face conditions. However, they have significant problems when they meet hard rock formations, such as high resistance to penetration, high wear and tear on the cutterhead, disc cutters, and screw conveyor, low muck flowability, and high chance of cutterhead damage. This document aims to give a comprehensive overview of the main challenges of 12 meters diameter EPB TBM tunneling through fresh granite, and some possible solutions and strategic approaches to deal with them, based on Barcelona Line 9 experience. The wear patterns observed in the elements involved in the excavation process are shown.
The wear patterns observed in the elements involved in the excavation process are shown. Systematic management and control of screw conveyor wear (including replacement for a new unit with latest high performance wear resistant steel in underground conditions), monitoring the wear evolution of the cutterhead perimeter area by using ultrasonic thickness measurement, as well as incidents recorded in the cutter’s housings due to the vibrations of the cutting wheel due to the hybrid rock/soil configuration when digging through massive granite.
