Relieved specific energy estimation using FLCM and PLCM linear rock cutting machines and comparison with rock properties

World Tunnel Congress, WTC 2019 and the 45th General Assembly of the International Tunnelling and Underground Space Association, ITA-AITES 2019 -- 3 May 2019 through 9 May 2019 -- -- 226789Specific energy is defined as the amount of work required to break a unit volume of rock and used to predict the performance of mechanical miners. This value can be obtained from full-scaled laboratory linear (FLCM) or portable linear rock cutting (PLCM) experiments at different cut spacings and depths, respectively. For this purpose, full-scaled linear and portable linear rock cutting experiments are performed on 5 different blocks of rock samples including Beige marble, Kufeki limestone, Travertine, Sandstone and Limestone. Cutter forces acting on a cutter in three orthogonal directions (cutting force, normal force, and sideway force) and, specific energy values are measured during testing. In addition, some physical and mechanical property testing are carried out and the relationships between optimum specific energy values and rock mechanical properties are analyzed using regression analysis. Statistical analyses suggest that the relieved specific energy values can be predicted reliably from rock mechanical properties to select the most efficient mechanical miners for a given rock or mineral. © 2019 Taylor & Francis Group, London.Türkiye Bilimsel ve Teknolojik Araştirma Kurumu Istanbul Teknik Üniversitesi ASCRS Research FoundationThis paper is based on the PhD thesis of Ramazan Comakli. The authors are grateful for the support of Istanbul Technical University (ITU) Research Foundation, the Scientific and Technological Research Council of Turkey (TUBITAK 112M859), the company of E-BERK Tunneling and Foundation Technologies for supplying mini discs and all research people involved in this project

Predicting performance of EPB TBMs by using a stochastic model implemented into a deterministic model

The current study is an attempt to address the stochastic nature of the rock excavation process by suggesting a stochastic performance prediction model implemented into a deterministic model developed for hard rock TBMs. Full-scale linear cutting experiments using constant cross-section and V-type of disc cutters are performed on two different limestone samples to provide the basic input required for the deterministic model used for estimation of instantaneous penetration rate, daily advance rate, thrust and torque requirements of TBMs. Stochastic estimation is performed by using a Monte Carlo simulation program by applying iterations to implement the probabilistic distribution of each model parameter and provide knowledge of a confidence level. Results of the suggested model are verified by measuring the field performance of two earth pressure balance (EPB) TBMs excavating competent rocks in semi-closed mode. The results indicate that the suggested model works well for prediction of instantaneous cutting/penetration rate for both TBMs and both types of disc cutters. However, an improvement on the model is required for estimation of cutterhead torque and thrust of EPB TBMs. The stochastic model implemented into the deterministic model results in almost similar predictions with the deterministic model in 50% (best guess) probability. However, the stochastic modeling provides a tool for exploring the full implications of linear cutting experiments and allows assessing the probability of occurrence and predicting variations of the TBM performance parameters, covering the uncertainties/risks. © 2014 Elsevier Ltd.A part of this article includes a part of Can Dayanc’s MSc dissertation. The authors are grateful to the support of Anadoluray Joint Venture, Gulermak-Dogus Joint Venture, and Istanbul Metropolitan Municipality; this work could be impossible without their support

Investigation into the Effects of Textural Properties on Cuttability Performance of a Chisel Tool

The main objective of this study is to investigate the effect of textural properties of stones on cutting performance of a standard chisel tool. Therewithal, the relationships between textural properties and cutting performance parameters and physical and mechanical properties were statistically analyzed. For this purpose, physical and mechanical property tests and mineralogical and petrographic analyses were carried out on eighteen natural stone samples, which can be grouped into three fundamentally different geological origins, i.e., metamorphic, igneous, and sedimentary. Then, texture coefficient analyses were performed on the samples. To determine the cuttability of the stones; the samples were cut with a portable linear cutting machine using a standard chisel tool at different depths of cut in unrelieved (non-interactive) cutting mode. The average and maximum forces (normal and cutting) and specific energy were measured, and the obtained values were correlated with texture coefficient, packing weighting, and grain size. With reference to the relation between depth of cut and cutting performance of the chisel tool for three types of natural stone groups, specific energy decreases with increasing depth of cut, and cutting forces increase in proportion to the depth of cut. The same is observed for the relationship between packing weighting and both of specific energy and cutter forces. On the other hand, specific energy and the forces decrease while grain size increases. Based on the findings of the present study, texture coefficient has strong correlation with specific energy. Generally, the lower depth of cut values in cutting tests shows higher and more reliable correlations with texture coefficient than the increased depth of cut. The results of cutting tests show also that, at a lower depth of cut (less than 1.5 mm), even stronger correlations can be observed between texture coefficient and cutting performance. Experimental studies indicate that cutting performance of chisel tools can be predicted based on texture coefficients of the natural stones