Comparison of drilling performance of chisel and button bits on the electro hydraulic driller

Electro hydraulic drillers have been widely used in mining for drilling and roof-bolting. In the drilling process, the performance of the machine is predicted by selecting an appropriate bit type prior to drilling operations. In this paper, a series of field drilling studies were conducted in order to examine and compare the performance of chisel and button bits including wear on the bits. The effects of taper angle on chisel bits, which are at angles of 105, 110 and 120, were investigated in terms of rate of penetration, instantaneous drilling rate and specific energy. The results of drilling and abrasivity tests performed in the laboratory supported the outcome of the field studies. Based on laboratory studies and field observations, it was proven that the conglomerate encountered, though it is very abrasive, is easy to drill. The cutter life in the encountered series is also longer in sandstone formation compared to the conglomerate. Additionally, button bits resulted in lower specific energy and higher penetration rates relative to chisel bits, regardless of their taper angles. The results were also supported with statistical analyses. © 2012 Springer-Verlag Wien

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

An integrated approach for the prediction of subsidence for coal mining basins

In this study, land subsidence caused by underground mining activities was investigated by means of a new subsidence prediction approach (ISP-Tech) which takes into account the most important parameters contributing subsidence development such as coal production methods, depth, mining sequence and other geomechanical characteristics of underground rock strata, etc. ISP-Tech can be applied to operating mines to keep land subsidence under control as well as virgin coal sites to predict surface subsidence prior to mining activities. In the method, geological information gathered from the geographic information system (GIS) and the mining information system (MIS) are utilised to obtain geological cross-sections which are used in finite element models for mesh building. Then, a number of two dimensional finite element modelling analyses are carried out to determine land subsidence occurring due to mining operations. Finally, land subsidence predicted from modelling studies is compared to the GPS and/or differential interferometry synthetic aperture radar (DIn-SAR) measurements. If incompatibility of the results is detected, finite element meshes should be optimised, and then reanalysed to obtain more compatible results. In the study, two different case studies were given as examples of the application of ISP-Tech. Results of the case studies showed that ISP-Tech can successfully be applied to complex mine subsidence problems. The proposed approach gives more accurate results than those obtained from other classical subsidence prediction methods. © 2013 Elsevier B.V

An evaluation of the impact strength index as a criterion of grindability

In this study, Hargrove Grindability Index and Impact Strength Index values of coals collected from 17 coal seams in the Zonguldak Hardcoal Basin were determined. Then, the effect of the Impact Strength Index test on grindability was examined by investigating the relationship between Hargrove Grindability Index and Impact Strength Index values. The results indicated that the best relationship between Hargrove Grindability Index and Impact Strength Index values was found to be in the form of a parabolic function, i.e., coals with high values of Hargrove Grindability Index and low values of Impact Strength Index are much easier to grind. Furthermore, investigations have been conducted as to the effect of volatile matter and carbon contents as well as the rank and maceral composition of the samples on Hargrove Grindability Index and Impact Strength Index values. As a result, it has been proven that Impact Strength Index values can be assessed as a criterion of grindability. Copyright © Taylor & Francis Group, LLC

The effects of a caries-removing get (carisolv) on FM3A cell-line in vitro

Objectives: The aim of this study was to examine the cytotoxic effects of Carisolv on mouse mammary carcinoma cell line (FM3A) at different application times

Relaxation on the Ismetpasa segment of the North Anatolian Fault after the Golcuk Mw = 7.4 and Duzce Mw = 7.2 shocks

The Ismetpasa segment of the North Anatolian Fault (NAF) is a rare place where aseismic fault slip (creep) has been observed. Its creep behaviour has been monitored using different observation methods since the 1950s. The findings obtained from the studies until 1990s showed that the creep rate exponentially decreased before the major shocks in 1999, Golcuk (Mw = 7.4) and Duzce (Mw = 7.2). After these shocks, three GPS periods observation in 2002, 2007 and 2008 were carried out on the geodetic network established around the segment. The evaluations of these observations showed that the creep behaviour relaxed after the major earthquakes. This result demonstrates that the creep behaviour of the Ismetpasa segment might be a warning before future major earthquakes. © 2010 Author(s)

Relaxation on the Ismetpasa segment of the North Anatolian Fault after the Golcuk M-w=7.4 and Duzce M-w=7.2 shocks

WOS: 000285577800019The Ismetpasa segment of the North Anatolian Fault (NAF) is a rare place where aseismic fault slip (creep) has been observed. Its creep behaviour has been monitored using different observation methods since the 1950s. The findings obtained from the studies until 1990s showed that the creep rate exponentially decreased before the major shocks in 1999, Golcuk (M-w = 7.4) and Duzce (M-w = 7.2). After these shocks, three GPS periods observation in 2002, 2007 and 2008 were carried out on the geodetic network established around the segment. The evaluations of these observations showed that the creep behaviour relaxed after the major earthquakes. This result demonstrates that the creep behaviour of the Ismetpasa segment might be a warning before future major earthquakes