Suggestion of new models for predicting performance of raise boring machines based on indentation tests

Raise Boring Machines (RBMs) as the fast, safe, and efficient machines are used for drilling/excavation of vertical and/or inclined shafts in the underground structures. Proper selection and accurate performance prediction of these machines are very important issues affecting the cost estimation and planning of the projects. However, due to lack of reliable models, performance prediction of these machines has been seriously limited. This study aims at proposing new models for performance prediction of RBMs based on indentation and full-scale linear cutting tests, as well as physical–mechanical property tests, performed on rock samples. Operational and performance data of RBMs and rock samples with different geological origins are collected from different raise boring projects. Then, indentation tests are performed on different core samples by using a real-life tungsten carbide insert of the button cutters used on the analyzed RBMs. Full-scale linear cutting tests were previously performed on the block samples by using a 305 mm (12 in.) diameter button (kerf) cutter. The study indicates that velocity of S-wave and Cerchar abrasivity index can be used to estimate brittleness index of rocks, which is also obtained from the indentation tests. It also shows the feasibility of using power function as relationship between the indentation force and penetration values for performance prediction of RBMs. It is shown that the results of indentation tests can be used in both empirical and deterministic predictions of RBM performance. However, the proposed models should be improved by additional rock types, operational-performance parameters of different RBMs, indentation and cutting test results of different rocks.