Theoretical and Experimental Results from Laboratory Tests by ILCM

Abstract

The intermediate linear cutting machine (ILCM) is a machine designed to work on an intermediate scale between the full- and the small-scale. The reduced scale involves several advantages compared to full-scale tests, especially in terms of sample supplying and transportation. On the other hand, it has an impact on the testing conditions, resulting in a limitation of the cutting penetration and spacing during the test, as well as in a smaller disc cutter. This affects most of the results, which cannot be directly used for the on-site machine performance prediction. However, some experimental results provided in the literature show that the optimal spacing/penetration ratio is not significantly affected by the changes involved. On this basis, the results obtained from ILCM tests should provide reliable information about the optimal cutting conditions of a tunnel boring machine in massive rock mass. The work performed included the development of some improvements of the testing rig, as well as a modified ILCM testing procedure, according to the one typically used in standard LCM tests. The results provide information about the attitude of the tested lithotypes to mechanical excavation by means of disc tools, including the optimal cutting conditions. Additional work was developed in terms of detailed characterisation of the rock samples involved and assessment of the size distribution of the debris produced during the ILCM tests. Nevertheless, further tests are necessary, in order to assess the consistency of the experimental procedure employed and to investigate the scale effect.

Investigation on rock cutting characteristics of spherical-tooth hob

“…Liu et al (2018a) conducted the rock indentation tests to study the effects of surface and internal crack propagation on rock breakages by TBM hob. Cardu et al (2021) discussed the optimal cutting condition and the size distribution of the debris combined with the cutting tests of the TBM hob. The rock cutting experiment of TBM hob is an effective method to investigate the rock breaking characteristics and its result can be applied in TBM engineering site directly, which has a good reference value for the optimal design and layout of TBM hob on rock cutting.…”