Investigation of parameters affecting vibration patterns generated during excavation by EPB TBMs

Abstract

Tunnel Boring Machines (TBMs) are widely utilized for infrastructure projects and they should be operated in accordance with the geological conditions for reaching favorable excavation rates. Therefore, recognizing any type of variance in the excavation conditions and responding properly and quickly have great importance. In that aspect, vibrations generated during mechanized excavation by Earth Pressure Balance (EPB) TBMs are analyzed and correlated with some parameters along the alignment in the present study. A special vibration data recording system is developed and installed onto four EPB TBMs, excavating in three different project sites. Vibration data on a total of 6 km tunnel excavation is recorded in three orthogonal directions and the effects of geological conditions including soils and hard rocks, EPB TBM operating parameters (thrust, torque, face pressure, cutterhead rotational speed, penetration rate), cutter damages/breakages, positions and types of accelerometers, and TBM diameters on vibration are investigated. Geotechnical characteristics of the investigated alignment are obtained from the geotechnical reports of the related sites. Following the detailed analysis of vibration characteristics (time domain parameters) and geotechnical data, it is seen that the vibration patterns generated during the excavation are greatly influenced by geological and lithological changes. The vibrations are also influenced by the TBM operational parameters and cutter conditions. It is realized that the broken disc cutters create specific high-amplitude signals. Generally, as the rock strength increases, TBM vibrations increase and the vibrations reduce greatly in weathered rocks and soils. These results indicate that TBM vibrations may be used for the identification of geological conditions and worn / broken cutters. The study can be further improved with additional data.