Effects of Cutter Types on Cutter Consumption and TBM Performance in Different and Complex Geological Conditions
EPB TBMs are widely utilized for infrastructure and transportation constructions in urban areas as mechanized tunneling is cost effective, safe and rapid when compared to other conventional methods. Today, as a result of technical improvements and increasing demand, design of TBM and cutter head, thus cutter type, cutter size and cutter layout vary in a wide range from manufacturer to manufacturer.Cutter tool maintenance and replacements are considered under main cost items in a TBM project. Cutter replacement is also a time consuming operation which affects project profitability and schedule. Since cutter tools directly affect the performance of TBMs, improper maintenance of cutter tools can lead to a reduction in daily advance rates. Moreover, in urban areas and difficult ground where earth pressure balancing is a necessity, maintenance programs should be planned carefully as it may require hyperbaric interventions which take a lot of time, effort and special equipment. As a result, carrying out such activities may become very difficult.Mahmutbey-Mecidiyekoy Metro Line is one of the unique projects in the world having 3 different TBMs operating in similar and complex geological conditions including saturated sand, claystone-siltstone, weathered to strong sandstone, fault lines, and mixed face conditions. Additionally, two of the TBMs had 17 inch CCS disc cutters while the other one had 15.5 inch V type disc cutters, which is very rare and used only in special occasions. One of the TBM’s cutterhead and disc holders took heavy damages during excavation in sandy ground which resulted in very low advance rates and a complete cutterhead replacement. In this paper, cutter tool consumption of the 3 TBMs has been compared and analyzed in detail along with encountered problems and other cutter related incidents. The data logs, shift reports and maintenance reports along with the geological reports and the TBM data have been carefully investigated and analyzed. The tunnel routes have been divided into sections where similar geological conditions were observed. A comparison in terms of cutter consumption were then made between 3 different TBMs of same size yet having different specifications, different cutter types and sizes. The aim is to provide a better understanding for the factors affecting cutter consumption and to compare the advantages and disadvantages of different cutter types and sizes in varying geological conditions.