Water jet tunneling: a theoretical advanced rate evaluation

Abstract Tunnel Boring Machines play an important role in the underground infrastructure execution of modern cities. They weigh thousands of tons and measure hundreds of meters besides utilizing high powered energy in the excavation process. Although being well established, they are based on a last century design approach and they are not compatible anymore with the sustainable concept that characterizes current society. An alternative is looking for news technologies capable of replacing the traditional cutter disc in the excavation process. This is the approach of Tunnels Laboratory - LabTun - of Santa Catarina University. In this context, one of the lastest developments is a water jet tunnel boring machine (WJTBM). It utilizes a high power water jet (hydrodemolition) combined with diamond wire to execute the excavation process in a lighter, smart and less powerfull way. Therefore, it is just as important to compare the proposed new concept with the alternatives. This study deals with this necessity by analysing its technological performance. The advanced rate index was chosen for this task. It was calculated by the NTNU prediction model for traditional TBMs and by a proposed method for LabTun's concept. This method envolves experimental results of volumetric removal rate for high power water jet and geometrical characteristics of water jet TBM. The analysis utilized four types of rocks (sandstone, slate, meta-sandstone and granite) as geologic scenarium. The results show a better performance of WJTBM for soft and porous rock and an inexpressive performance for hard rock.