Yilmaz Ozcelik

Statistical and microscopic investigation of disc segment wear related to sawing Ankara andesites

Despite the advancement in the technology, and the introduction of many synthetic materials, hard rock still keeps its vital importance in daily constructive and decorative consumption. The hard rock processing sector has shown a rapid development since 1930. Turkey has also been affected by this development and many numbers of hard rock processing factories have been established in the last 15 years. The import of basic machines, equipment and consumables in these factories constitutes a major economic problem in this sector. Disc consumption is the most important economic expenditure during the processing of hard rocks. Unsuitable manufacturing of discs and inappropriate adjustment of machine parameters to the rocks to be cut, causes the discs to deteriorate rapidly, leading to eventual economic loss [1]. The circular diamond saw blade contains a steel core which has diamond impregnated segments brazed on the periphery (Fig. 1). The segments (metal bonds) have two basic functions. These are to hold the diamond tight and to erode at a rate compatible with the diamond loss. Due to a large variety of sawing conditions many metal matrix compositions are in general use. Bonds based on copper, various bronze compositions, and on cobalt, tungsten, and tungsten carbide as well as combinations thereof cover a wide range of stone sawing applications. Sometimes small additions of iron, nickel, etc. are made to aid the manufacturing process or in the belief that the addition improves diamond retention or matrix wear properties; however, the complexity of compositions encountered in production practice, which in same cases comprise seven components, makes a scientific approach to the total problem extremely difficult or even impossible [2]. In general, many factors affect the stone cutting by a circular saw blade. These factors can be written in three groups (as shown in Table 1) [3]. The first important factor is the engineering properties of the material. The clue of the suitable values of parameters to reach the effective result is constant parameters. The physico-mechanical, mineralogical and petrographical properties must be analyzed before the sawing test and these results must be used in the producing part of the segment and saw blade. The performance of the sawing with a disc cutter is affected by diamond type, the size of diamond, the concentration of diamond and the properties of the metal bond (matrix). In general, the diamond crystals must have sufficent strength to withstand the repeated cutting forces during the granite sawing process. If the diamond is too weak in strength, it will easily produce macro-cracks and crushed particles. It will also cause the blade to act hard so that possibly glazing will occur. Conservely, if the diamond has very high strength and toughness, it will be difficult to fracture it to produce new cutting points and edges. In addition, it will be polished to give the blade a glazed appearance. The choice of the optimum diamond type for a given application depends on many factors, such as the stone type, the cutting conditions, the type and the quality of the machine, etc. [4]. Luo and Liao [4] report that various studies have been conducted to investigate the effects of the diamond type and size of wear and sawability in the processing of stone with diamond saw-blades. Jennings and Wright [5] stated that hard materials usually require a smaller size diamond than do softer stones because the load per particle is not sufficiently high and greater clearence is required for swarf. Conversely, if large diamond grits are used on hard materials, the penetration of the *Corresponding author. Department of Applied Science, University of Arkansas at Little Rock, Arkansas 72204, USA. Fax: +1-501-5698020. E-mail address: aseyuboglu@ualr.edu (A.S. Eyuboglu).

Prediction of engineering properties of rocks from microscopic data

The purpose of this study is to develop the empirical equations for the prediction of the physical and mechanical properties of limestone and marble from microscopic data including their mineralogical and petrographical properties and to test the validity of model equations by using multivariate statistical methods. This study was performed on 15 different rocks, composed of six limestone and nine marble samples. Stepwise multiple regression analysis was applied to predict the engineering properties of both the marble and limestone rock samples considering petrographical properties as inputs. In order to determine the overall significance of the empirical equations for prediction of the physical and mechanical properties of marble and limestone samples, the F test was also performed. As a result of this study, it is found that the empirical equations developed in this study are statistically significant.

The Effects of Operational Parameters on a Mono-wire Cutting System: Efficiency in Marble Processing

Mono-wire block cutting machines that cut with a diamond wire can be used for squaring natural stone blocks and the slab-cutting process. The efficient use of these machines reduces operating costs by ensuring less diamond wire wear and longer wire life at high speeds. The high investment costs of these machines will lead to their efficient use and reduce production costs by increasing plant efficiency. Therefore, there is a need to investigate the cutting performance parameters of mono-wire cutting machines in terms of rock properties and operating parameters. This study aims to investigate the effects of the wire rotational speed (peripheral speed) and wire descending speed (cutting speed), which are the operating parameters of a mono-wire cutting machine, on unit wear and unit energy, which are the performance parameters in mono-wire cutting. By using the obtained results, cuttability charts for each natural stone were created on the basis of unit wear and unit energy values, cutting optimizations were performed, and the relationships between some physical and mechanical properties of rocks and the optimum cutting parameters obtained as a result of the optimization were investigated.

Impact of Overcut on Interaction Between Shield and Ground in the Tunneling with a Double-shield TBM

Double-shield TBMs (DS-TBM) are among the most technically sophisticated excavation machines in use by tunneling industry. The use of shields around the TBM allows the machine to pass through weak grounds and adverse geological conditions. However, there are limitations in applicability for DS-TBM in some ground conditions where large deformations are anticipated. The presence of the shield limits access to the tunnel walls for observation of ground conditions. This means limited possibilities of observing and analyzing ground conditions to avoid certain problems. Similarly, the presence of the shield does not allow the intrusion of the ground into the tunnel envelope, which is the main objective of using a shielded machine in the first place, yet it also creates the possibility of ground pressing against the shield. In such conditions, TBM may get stuck (including shield jamming and cutterhead blocking) in complicated geological structures, especially under high ground cover or in weak rocks, where large convergences are expected. This could cause major delays and impose a heavy and expensive burden on the tunneling operation. Some of the issues related to application of DS-TBMs in squeezing ground have been discussed in Hasanpour (2014) and Hasanpour et al. (2014a, b) and some possible scenarios and concepts for mitigating the related problems are offered. There are several performance parameters that should be considered with high accuracy at the design stage of a TBM for preventing machine entrapments. Size of the annular space or gap between ground and shields (created by overcut), length and diameter of shields, thrust force and torque, and machine advance rate are the most important performance parameters in tunneling by a shielded TBM. However, selecting the correct overcut, compared to other performance parameters, has a significant impact on preventing shield jamming. Selecting an appropriate or optimum value for overcut at the design stage of DS-TBM tunnel and implementing the predetermined overcut is the easiest way to address machine jamming, with the possibility of adjustment along the tunnel by using movable gage cutters. The adjustments can be directly related to ground properties and optimized to reduce the risk of machine jamming, while minimizing both the amount of material that is excavated and hauled out of the tunnel and the amount of grout that is placed behind the segments. For preventing the shield seizure, increasing the annular gap between the rock and shield is often utilized at the machine design stage. This feature can be included in the design of the cutterhead to accommodate a given overcut as a base design, and as needed, the excavated diameter of the tunnel, and hence the gap above the shield can be increased to react to bad ground where large convergences are & Rohola Hasanpour roha93@gmail.com

Investigation of surface and subsurface displacements due to multiple tunnels excavation in urban area

Underground structures are currently widely used and are built as urbanism develops. The interactions between perpendicularly crossing and parallel tunnels in the Tehran region are investigated by using a full three-dimensional (3D) finite difference analysis with elastic-plastic material models. Special attention is paid to the effect of subsequent tunneling on the support system, i.e., the shotcrete lining and rock bolts of the existing tunnel. Eventually, as the tunnels are excavated at certain levels, the interaction between the tunnels will certainly have a significant influence on both stress distribution and consequently deformations. Since multilayer tunneling is a three-dimensional phenomenon in nature, 3D numerical solutions must be utilized for analyzing effect of perpendicularly crossing tunnels at various levels. As Tohid twin tunnels and Line 7 pass beneath the Line 4 metro tunnel, changes in stress distribution, deformations, and surface settlements are studied for various conditions and the results are presented in this paper. Consequently, it is shown that there is a significant interaction between tunnels that necessitate certain preventive measures to maintain a stable tunneling operation.

Analysis of bead wear in diamond wire sawing considering the rock properties and production rate

Predicting the wear rate of diamond beads in the diamond wire sawing process is one of the most important factors in the optimized design and cost estimation of quarrying. This paper aims to predict the wear rate of diamond beads as one of the principal performance criteria in dimension stone quarrying. Saw operating parameters and mechanical and physical properties of rock are the most effective factors on diamond bead wear. In the same working conditions (at constant operating parameters), the wear rate of diamond wire saw is strongly affected by the production rate, and the characteristics of rock. In this study, the uniaxial compressive strength, Schmiazek abrasivity factor, Mohs hardness, and Young’s modulus were selected as the main physical and mechanical properties of rock. The 11 types of igneous rocks were cut in the laboratory using a diamond wire saw and a fully instrumented cutting platform. During the cutting process, the wear rate of diamond beads were determined after each cutting test. The wear rate of diamond bead and rock characteristics were evaluated using simple and multiple curvilinear regression analysis, and prediction models were developed. The developed models were validated by considering the t-test, F-test, correlation coefficient and the plots of predicted versus actual values. The results indicated that the wear rate of diamond beads can be reliably predicted using the developed model.

Optimization of limestone sawing using circular saws with reference to unit wear and energy

Natural stone processing operations use different methods and machines; however, the circular sawing machines are widely used in natural stone processing since they can be used flexibly. The wear on the diamond segments on the sawblade and energy consumption are the important parameters for these machines. Unit wear and unit energy should be minimized and the sawing rate should be maximized for optimum sawing condition. In this study sawing tests were performed on limestone samples using a fully automatic circular sawing machine. The tests were conducted at different peripheral speeds and advance rates. For each sawing test, the segment wear and consumed energy were measured. The statistical software, Design Expert 7.0 was used to analyze the test data. The new sawability charts for wear and energy were developed. The unique aspect of this study is to determine the optimum circular sawing performance with the special software and this technique also provides the prediction of unit wear and unit energy for selected sawing condition.

Predicting the Building Stone Cutting Rate Based on Rock Properties and Device Pullback Amperage in Quarries Using M5P Model Tree

One of the key parameters that affect the selection of equipment and the cost estimation of dimension stone quarries is the rock cutting rate or production rate. In this study, the M5P tree algorithm is used to determine the relationship between the hard rock sawability and its factors especially the physical and mechanical characteristics of rock. To achieve the research goal, a variety of eleven types of hard dimension stone were selected and nine major physical and mechanical characteristics of rock including uniaxial compressive strength, Young’s modulus, Brazilian tensile strength, equivalent quarts content, grain size, Mohs hardness, point load test, density and P-wave velocity of these samples were evaluated. The cutting rate of diamond wire for all of the Workpiece was measured at different pullback amperage with a fully instrumented cutting platform in laboratory. All operational parameters of cutting process were entirely controlled. Thus, a database containing 99 datasets was provided and it has been used for analyses. The obtained results from the pruned and unpruned tree models showed a significant relationship between cutting rate and its factors. In the end, the results of M5P tree method were compared with statistical analyses (i.e., linear and nonlinear regression). The coefficient of determination be equal with 0.92, 0.86, 0.77 and 0.63 for unpruned tree, pruned tree, linear and nonlinear regression method respectively. This comparison showed that the both method of M5P tree technique have a better performance in predicting the cutting rate rather than the statistical regression methods.

DEM modeling of a monowire cutting system

Monowire block cutting machines can be used for natural stone block squaring and slab cutting operations. The plants where the cutting operations are performed demand high product quality with minimum operational costs. The major parameters affecting the economy of the operation are the energy consumed and the wear induced on the diamond beads during the cutting operation. An efficient cutting operation can only be maintained by selecting proper cutting parameters. Therefore, cutting parameters should be clearly understood. Experimental studies and numerical modeling methods are significant in terms of identifying the energy consumption occurring during natural stone cutting with monowire. Experimental studies and numerical modeling using discrete element method were performed on Afyon White Marble. Experimental studies have been performed by using a specially designed, fully automatic monowire cutting machine, and numerical analyses were carried out by commercially available software called three-dimensional particle flow code (PFC3D). A discrete element model for the cutting operation was developed, and various numerical models were performed for different peripheral speeds and cutting speeds, while, at the same time, the actual cutting operations were being carried out in the laboratory. Finally, the data obtained from the experimental works were compared with the data from numerical modeling. A comparison indicates that the frictional energy values obtained by means of numerical modeling are in good agreement with the results of the laboratory measurements. This study clearly put forward the influences of effective parameters on monowire cutting operations in natural stone industry. Furthermore, it filled an important space in the literature about the use of monowire block squaring machines.

Developing a new rock classification based on the abrasiveness, hardness, and toughness of rocks and PA for the prediction of hard dimension stone sawability in quarrying

Abstract Predicting the sawability of dimension stone is one of the most important factors in the optimized design and cost estimation of quarrying. This paper aims to predict the cutting rate of diamond wire saw (DWS) as main performance criteria. For this purpose, a classification system for ranking the sawability of hard dimension stone based on the toughness, abrasiveness, and hardness of rock was initially developed, and a Hard Dimension Stone Sawability index (HDSSi) was defined. Then, by means of multiple curvilinear regression analysis, the data were analyzed and the relationship between the cutting rate with the HDSSi, and pullback amperage was obtained with a high correlation coefficient (.846) in data training, and .801 in data test. Validation of the model was carried out by considering the t-test, F-test, and the coefficient of determination. During this research, varieties of 11 types of hard rock were cut in a laboratory using a DWS and a fully instrumented cutting platform at different pullbacks. The results show that the cutting rate of hard dimension stones with a DWS can be successfully predicted using the developed model.