Use of Indentation Tests to Study the Rock Breaking Mechanisms Induced by a TBM Disc Cutter
MetadataShow full item record
Since the introduction of mechanical tunnel excavation technology, there has been conducted numerous theoretical, empirical and experimental studies to explain the interaction between rock and mechanical cutting tools. Previous RPM trials and observations made at the Lower Røssåga Hydropower Project suggests that running the TBM at a lower RPM gives a higher basic penetration per cutterhead revolution, and that the rock breaking process becomes more efficient. \noindent The purpose of this thesis is to study the TBM rock-tool interaction, and provide information and data to be used in the work of PhD student Solveig Vassenden and the FAST-Tunn Project. In this thesis, special attention is directed towards RPM and its effect on rock breaking processes and TBM performance. Through comprehensive laboratory testing, the correlation between RPM and fracture mechanisms in a core samples collected has been investigated. This correlation is studied through indentation tests with a modified point load-testing unit. The indentation tests are performed with different loading rates in order to simulate different RPMs on a TBM. In order to detect new fracture formation in the core samples subjected to loads from a TBM disc cutter, sound wave velocity measurements are carried out. The results of the indentation tests seem to coincide with the observations made at Lower Røssåga Hydropower Project. Based on visual observations, sound velocity measurements and statistical analyses, the measured fracture depths in the tested core samples show a clear tendency to decrease with increasing loading rates. Due to time constraints and a relatively limited sample size, it is highly recommended to conduct supplementary testing to be able to draw viable conclusions.