Scale factors for conversion of forces on disc cutters for the main domestic and foreign methods

Purpose.Disc cutter is an important tool which is used in tunneling to destroy the rock during excavation as it directly influences rock-breaking efficiency, advance rate and economy of a project. Thus, it is of critical importance to have a reliable and accurate method for making predictions on cutting forces during rock destruction by disc cutters. Russian (including Soviet) research in the field is limited by studying small-diameter and/or wedge-shaped disc cutters which are not currently used. This paper is meant to coordinate domestic research by Baron and Glatman with the most widely used and fully accepted foreign theoretical and semi-empirical methods (by Roxborough and Phillips, Bilgin and Phillips, and Rostami and Ozdemir) that have proven accurate and reliable for TBM (tunnel boring machine) performance prediction. Methods. The analysis of methods includes a brief review, a series of numerical experiments, which were performed for disc cutters with diameters 160 mm and 483 mm, and a comparison with the use of graphs. Then by approximation of the data obtained in this way, we have derived formulas for converting values of cutting forces gained by foreign methods into the values suitable for the same conditions and the domestic method. Findings. The method by Baron and Glatman itself could not be used for TBM performance prediction and tunneling planning nowadays. The approach based on the scale factors could be used for correlating any of the represented methods. Scale factors depend on the depth of cut (DOC) for rolling forces or on DOC and disc cutter diameter for normal forces. Originality.The analysis has also shown that mutual arrangement of the graph lines for all figures remains unchanged. The invariance of the relative positioning and trends of the graph lines allowed to assume that it is possible to introduce scale factors which help to convert values from one method into the values of other methods. The scale factor, which enables to relate domestic method and the main foreign methods, is determined by consecutive division of the calculated values obtained via the method of Baron and Glatman by the values used in other considered methods. Practical implications. The results could be used in TBM designing and in tunneling projects.