TECHNICAL NOTE Application of RMR for Estimating Rock-Mass–Related TBM Utilization and Performance Parameters: A Case Study O. Frough • S. R. Torabi • S. Yagiz Received: 5 September 2011 / Accepted: 23 May 2014 / Published online: 24 June 2014 Ó Springer-Verlag Wien 2014 Keywords RMR system Á TBM performance Á Utilization List of symbols Alpha (a) The angle between tunnel axis and the planes of weakness AR Advanced rate BI Brittleness index BTS Brazilian tensile strength BWI Bit wear index CLI Cutter life index CAI Cherchar abrasivity index CCS Constant cross section CSM Colorado School of Mines Model DPW Distance between planes of weakness DRI Drilling rate index FPI Field penetration index GRRD Geology and rock related downtime MCSM Modified Colorado School of Mines Model NTNU Norwegian University of Sciences and University ORD Other related downtime Q Rock mass classification system Q TBM Modified Q system RME Rock mass excavation index RMi Rock mass index RMR Rock mass rating ROP Rate of penetration RQD Rock quality designation RSR Rock structure rating U (%) Utilization UCS Uniaxial compressive strength 1 Introduction Prediction of tunnel boring machine (TBM) performance is crucial for mechanized tunneling, since TBM perfor- mance has an influence on duration and costs of the project. Analysis of TBM performance includes the assessment of the rate of penetration, advance rate and utilization, (the percentage of shift time that actual boring activity occurs). Inaccurate estimation of the utilization factor may cause major project delays and commonly results in large claims. Performance and utilization of TBM depend on many factors that can be categorized as machine specifications, operating parameters and rock mass conditions encountered along the tunnel. It is rather complicated to identify which factors have a prominent effect on TBM performance. Even small changes in machine operation or geological complexity can have a significant effect on machine performance. As a result, it is difficult to estimate TBM utilization accurately under variable rock mass conditions. TBM utilization and per- formance parameters depend not only on the rock mass properties, but also on machine specification, manpower, organization of the construction site, shift time and so on. In this study, the relationship between the rock mass conditions, essentially described by rock mass rating system (RMR), and TBM performance parameters is examined using data collected from 16-km long Karaj water conveyance tunnel Lot-1 (Tehran, Iran). O. Frough Á S. R. Torabi Shahrood University of Technology, Shahrood, Iran S. Yagiz (&) Geological Engineering Department, Pamukkale University, Denizli, Turkey e-mail: syagiz@pau.edu.tr 123 Rock Mech Rock Eng (2015) 48:1305–1312 DOI 10.1007/s00603-014-0619-4