Numerical simulation of rock cutting using the discrete element method

In this study, an attempt was made to model rock cutting tests. For this purpose, a computer program named Particle Flow Code in 3 Dimensions (PFC3D) was used. In order to numerically predict tool forces from cutting tests in PFC3D, graded particle assemblies were created, and the micro-properties were calibrated by modeling the uniaxial compressive strength test. Following the model creation procedure, the conical (point attack) pick was positioned and advanced with a constant velocity. The tool forces acting on the pick were recorded during the simulations. Moreover, the peak cutting forces were calculated by utilizing the theoretical equations proposed by researchers and the results of experimental studies were given as well. Consequently, the mean peak cutting forces, which were obtained from numerical, experimental and theoretical models, were compared. The relationships between these models were investigated and supported with the regression analysis. It was pointed out that there is a strong correlation between the modeling, experimental and theoretical studies. © 2010 Elsevier Ltd

Cuttability characteristics of some high strength rocks for roadheader selection in Zonguldak Coalfield

10th International Symposium on Mine Planning and Equipment Selection (MPES) -- NOV 19-21, 2001 -- NEW DELHI, INDIAWOS: 000176775500109Hard coal is only exploited in Turkey in Zonguldak Coalfield and mining activities are carried out since 1848. The expected coal reserves are 1.3 billion tons, The annual production of the coal decreased dramatically for the last ten years due to the geological difficulties. However, many research works were carried out in the last years to increase the annual production and to decrease the production cost. The roadways are mainly driven in high strengths rocks with drill and blast methods, The research results discussed in this paper is a summary of a research work sponsored by The Research Fund of the Karaelmas University with the support of the Mining Engineering Department of The Technical University of Istanbul. Systematic rock samples from the rock strata were collected from the mine and these samples were subjected to the various mechanical and physical tests. These are sandstone, mudstone, shale and limestone, having compressive strength values up to 170 MPa. In the later stage, samples having size of 0.7x0.7x0.5m were subjected to the full-scale cutting tests in the laboratories of Mining Engineering Department of The Technical University of Istanbul within the facilities provided by NATO-TU Excavation Project. The cutter forces and specific energy values for different depth of cut and cutter spacing were recorded. Later, the results were discussed for the application of roadheaders equipped with conical bits and mini discs within the light of present and other ongoing research projects

Dominant rock properties affecting the performance of conical picks and the comparison of some experimental and theoretical results

Conical picks are the essential cutting tools used especially on roadheaders, continuous miners and shearers and their cutting performance affects directly the efficiency and the cost of rock/mineral excavation. In this study, in order to better understand the effects of dominant rock properties on cutter performance, 22 different rock specimens having compressive strength values varying from 10 to 170 MPa are first subjected to a wide range of mechanical tests. Then, laboratory full-scale linear cutting tests with different depth of cut and cutter spacing values are realized on large blocks of rock specimens using one type of conical pick. Specific energy, cutting and normal force values for relieved and unrelieved cutting modes are recorded using a triaxial force dynamometer with capacity of 50 tonnes and a data acquisition system. Cutter force and specific energy values are correlated with rock properties and theoretical force and specific energy values obtained from widely used theoretical approaches. The results indicate that uniaxial compressive strength among the rock properties investigated is best correlated with the measured cutter performance values, which is in good agreement with previous studies. However, it is also emphasized in this study that Brazilian tensile strength, Schmidt hammer rebound values, static and dynamic elasticity modulus are also dominant rock properties affecting cutter performance. Theoretical specific energy defined by different researchers has a mean ingful relationship with the experimental specific energy, which is an essential parameter for predicting the instantaneous cutting rates of mechanical excavation systems. It is also demonstrated that the experimental cutter forces obtained for 5 mm depth of cut are in good agreement with theoretical force values, if the friction angle between rock and cutting tool is included in the theoretical formulation. It is emphasized that, to some extend, laboratory tests can help to minimize high cost of a trial-error approach in the field. © 2005 Elsevier Ltd. All rights reserved.North Atlantic Treaty Organization Devlet Planlama Örgütü Magyar Tudományos AkadémiaThis paper is a summary of a research programme carried out in Istanbul Technical University, Mining Engineering Department during the last 8 years. The research was sponsored by NATO Sfs programme, the Turkey Republic Prime Ministry State Planning Organization (DPT), Istanbul Technical University Research Fund, Karaelmas University Research Fund and General Directorate of Mineral Research and Exploration (MTA). The authors acknowledge Prof. Dr. Levent Ozdemir from the Earth Mechanics Institute of Colorado School of Mines and all the research staff involved without their help and work, this contribution to rock cutting mechanics could not be possible

Co-infection relationship with Epstein-Barr virus in gastroduodenal diseases with Helicobacter Pylori. Quantitative PCR and EBNA-1 gene-based approach

Objective: Helicobacter pylori (Hp) and Epstein-Barr virus (EBV) are involved in gastric cancer (GC) etiology. EBV/Hp co infection was thought synergistically increase gastroduodenal disease occurence. We aimed to determine the presence of EBV/Hp co-infection in gastroduodenal diseases. Methods: The study group had 68 Hp (+) cases [25 GC, 13 IM (intestinal metaplasia), 30 PU (peptic ulcer)], and the control group had 40 NUD (non-ulcer dyspepsia) cases [20 Hp+, 20 Hp-]. EBV-DNA was detected by non-polymorphic EBNA-1 gene-based qPCR. EBV/EBNA-1 IgG levels were determined by quantitative and qualitative ELISA methods, respectively. Results: EBV-DNA positivity was 32% (8/25), 6.6% (2/30) and 5% (1/20) in GC, PU and NUD Hp (+) cases, respectively. There was a significant difference (p = 0.001) between GC (32%) and NUD Hp (+) (5%) cases in terms of EBV-DNA positivity. Mean EBV-DNA copy numbers were 6568.54 ?? 20351, 30.60 ?? 159.88 and 13.85 ?? 61.93 for GC, PU, and NUD, respectively. In terms of the mean EBV-DNA copy number, a significant difference was found between the groups (p = 0.005). In terms of EBV/EBNA-1 IgG antibody positivity, no significant difference was found between GC and NUD cases (p = 0.248). EBV DNA positivity was found to be significant (odds ration [OR] = 26.71 (p=0.009, %95CI 2.286312.041) in multivariate logistic regression. Conclusio??n: Although we had a small number of GC cases, it can be suggested that the estimated risk created by the synergistic effect based on the addition of EBV increased 26 times in the presence of Hp in GC. (Acta gastroenterol. belg., 2022, 85, 301-308)