Evaluation of tool wear in EPB tunneling of Tehran Metro, Line 7 Expansion

The total number of EPB-TBMs that were utilized for tunneling between 2005 and 2010 is approximately 350 units worldwide. One of the most critical adverse conditions is encountering abrasive soils and excessive wear on the cutting tools and the cutterhead as has been reported in many EPB tunneling projects worldwide. In this project, the number of cutting tools replaced were 1169, including 654 rippers, 357 scrapers and 153 disc cutters. In this paper the influence of geological parameters and operational factors on tool wear is studied. The objective of the current study was to investigate tool wear on EPB machines through a case study and field measurements. This refers to assessment of the fundamental reasons for increases of TBM tool wear in certain ground conditions to find a correlation between geological conditions and operational parameters with cutter life in soft ground tunneling. This paper introduces the subject tunnel project in this case study, describes the Cutter life parameters as observed in this project and presents results from TBM operation’s and soil properties and their influence on tool wear. The results of this study show that by increasing TBM thrust, earth pressure and torque, the cutter consumption generally increases. Also, soil conditioning plays an important role in controlling cutter wear, so that the tool wear can be reduced even in coarse-grained soils by improving the soil conditioning parameters.