Investigation into the effects of different rocks on rock cuttability by a V-type disc cutter

Abstract

Abstract This paper is about to investigate the effects of different rock structural properties and a V-type disc cutter on rock cuttability. The cutter having 381 mm in diameter, 90° edge angle and 1.4 mm tip radius is selected for linear rock cutting tests. Rock samples obtained from tunnels in Istanbul are subjected to physical and mechanical tests and rock cutting tests using V-type disc cutter. Three rock types – arcose, shale and fossilized limestone – representing almost same strength values in contrast to different rock structural properties are subjected to rock cutting tests. Rock cutting test results are compared with V-type disc theory proposed by Roxborough and Phillips (1975) and empirical equations developed by Bilgin (1977) . The field performance of a Lovat TBM equipped with V-type disc cutters is recorded and some recommendations are presented to tunnel contractors and practicing field engineer. Field boring parameters can be reproduced in the laboratory and theoretical results can be used taking into account rock cutting tests for performance prediction. Experimental rock cutting, field and theoretical results are compared with respect to rock cutting science. The results show that besides rock strength parameters, rock texture, grain size, mineralogy has an effect on the rock cutting parameters. The efficiency of V-type disc cutter in non-abrasive and medium strength rocks is also compared with CCS type disc cutter using some theoretical concepts. These factors should also be taken into account during the laboratory, field and theoretical calculations. As a result it is concluded that V-type sharp edge of disc cutters is very efficient tool in practice for TBMs if the formations include medium to soft strength and non-abrasive rocks.