TBM performance analysis in very strong and massive rocks; case study: Kerman water conveyance tunnel project, Iran
Seyed Mahdi Pourhashemi, Kaveh Ahangari, Jafar Hassanpour, Seyed Mosleh Eftekhari
Abstract
When TBMs are applied for tunnel excavation in very strong and massive rocks, the cutting mechanism happening under the disc cutters is converted from chipping to grinding. On the other hand, the most common TBM performance prediction models that have been developed assuming the occurrence of the chipping phenomenon would not be sufficiently accurate in grinding conditions. Therefore, this study aimed to develop a new empirical equation for estimation of the TBM performance in grinding conditions. In this regard, the database composed of actual measured TBM parameters (i.e. penetration rate and cutter load) and engineering rock properties (i.e. UCS, RQD in rock mass) was established using the data collected from a mechanised tunnelling project (the southern lot of Kerman water conveyance tunnel project, Iran) constructed in very strong rocks. Based on the established database, the statistical analyses were performed in order to develop a new TBM performance prediction model for grinding conditions. The proposed model provides a relationship between TBM penetration and cutter load for strong (UCS = 150–300 MPa) and massive rocks (RQD > 90) under grinding conditions.