A method based on extensive laboratory and field measurements was developed to determine the dependence of specific rock cutting energy (SEc) on specific drilling energy (SEd) for machines with ...different operating and design characteristics and similar breaking mechanics. Laboratory measurements were performed on a linear rock cutting device and a laboratory drill, using a measurement system to measure electrical power and cutting forces using force/torque transducers. Field power consumption measurements were performed on a chainsaw cutting machine and a hydraulic rotary drill under real working conditions in the dimension stone quarries. The analysis of the measured results confirmed the strong dependence of the specific rock cutting energy on the specific drilling energy and confirmed that laboratory devices can be used to simulate actual rock cutting and drilling process. In addition, the results are applicable in the dimension stone exploration and exploitation phase in order to assess and reduce energy consumption by optimizing the operating parameters of the chain cutter and/or the hydraulic rotary drill.
Dimension stone is a valuable mineral raw material whose importance is increasing worldwide. According to its mineralogical and petrographical composition, Croatian dimension stone belongs to the ...carbonates, primarily limestones. As saturation influences the reduction of compressive strength, in this study, the relationship between the uniaxial compressive strength in the dry and saturated states is shown, which has a coefficient of determination of 0.9605. Models were created to estimate the compressive strength based on the values of water absorption, total porosity, and real density of the material from 26 sites, all determined according to the European standards EN 1936:2006 and EN 13755:2008. Thirty varieties of dimension stones were tested, and 150 values were collected from different tests. A dependence between the uniaxial compressive strength in the saturated state was established, including the explanation in which cases the correlation can be used to estimate the uniaxial compressive strength of carbonate dimension stones with a remarkably high degree of confidence (0.994 and 0.9374). In addition, the limitations of geomechanical estimation of the uniaxial compressive strength of rock material and its unsuitability for estimating of dimension stones construction are described.
Among many factors that influence an excavator’s performance and productivity, the volume of the bucket load and duration of the excavator working cycle are crucial. In this paper, both factors were ...investigated, including the granulometric composition of the excavated material. The volume of material in the bucket was determined by photogrammetric analysis while the excavator cycle time was measured by analysis of video recordings captured by a digital video camera during the excavator operation. Interconnections between the angle of repose, slewing angle, particle size distribution of material, and their effects on hydraulic excavator productivity were analyzed. It was found that a larger number of fine particles in granular materials with a higher coefficient of uniformity resulted in an increase in the volume of the bucket load. Correlation analysis revealed significant interconnection between the bucket fill factor and swell factor. It was also found that calculation of the production rate according to ISO (International Organization for Standardization) standards was more accurate for materials with a higher angle of repose while the CECE (Committee for European Construction Equipment) standard was more appropriate for materials with lower angles of repose.
Diamond wire saws are indispensable machines for the extraction and processing of dimension stones. The cutting speed, energy consumption and wear rate of the diamond beads are the most important ...factors in assessing the efficiency of a diamond wire saw. The parameters that influence the efficiency of the diamond wire saw can be divided into controlled and uncontrolled parameters. Uncontrolled parameters cannot be influenced directly and are related to the rock types and their properties such as strength, hardness and abrasiveness. Controlled parameters are related to the operating parameters and technical characteristics of the machine. The energy consumption and the service life of the diamond wire are directly related to the characteristics of the machine and the design of the diamond wire, such as the power of the drive motor, the diameter of the drive wheel, diamond grit size and the diameter of the wire. The operating parameters of the diamond wire saw, such as cutting speed, cutting surface, cutting angle, wire tension and cooling water flow, also have a significant influence. Based on previous studies, the influence of the above parameters on the consumption of energy and wear rate of diamond beads in the operation of a diamond wire saw was analyzed.
Tensile strength of intact rock materials has been determined by the indirect method more frequently than by the direct method. This paper presents a historical review of the development of the ...indirect method called the Brazilian test, comprising the period from 1943 to the present day. It stresses some aspects which are essential for interpreting the results of the Brazilian test due to the different degrees of stress during the testing and the direct method of determining tensile strength. The estimate of the direct tensile strength and the influence of sample saturation on the results of indirect tensile strength testing have been specifically elaborated.
Specific energy is the measure which connects the operating parameters of a machine with the characteristics of the rock in which the machine works and is equal to the total work required to break a ...unit volume of the rock. It is assumed that in machines with the same or similar rock breaking mechanics used for different purposes (e.g. cutting and drilling of rocks), there is a significant dependence on their specific energy values. In the exploitation of dimension stone a chain saw and a rotary drill are often used, i.e. the machines for rock cutting or rock drilling whereas their mechanics of rock breaking are very similar. In order to determine the dependence of the specific energy of rock cutting on the specific drilling energy, preliminary laboratory tests were carried out on a linear cutting machine and a laboratory drilling rig with simulated cutting of rocks with a chain saw, and drilling by rotary drilling rig. The analysis of the measurement results has provided the guidelines for the continuation of laboratory testing, i.e. field testing.
There are a number of methods for estimating physical and mechanical characteristics. Principally, the most widely used method is regression, but recently, more sophisticated methods such as neural ...networks have frequently been applied as well. This paper presents the models of a simple and a multiple regression and neural networks –types Radial Basis Function and Multiple Layer Perceptron, which can be used for the estimate of the Brazilian indirect tensile strength in saturated conditions. The paper includes the issues of collecting data for the analysis and modelling and an overview of the performed analysis with an efficacy assessment of the estimate for each model. After the assessment, the model which provided the best estimate was selected, including the model which could have the most wide-spread application in the engineering practice.
The cutting design of the chain saw is defined by the number, the arrangement and the geometry of the cutting tools. When using chisel cutting tools, the cross sectional area of the cut and the shape ...of the groove are determined by the width and depth of the cut. The laboratory tests analyzed the impact of the cross sectional area and the shape of the cut on the forces and the specific energy. The testing was performed on a linear cutting machine with tool holders and cutting tools in real-scale size. According to the processed statistical data, increasing the cross sectional area of the cut reduces the specific energy, whereby the width of the cut has a considerably larger impact. The tests have shown that besides the cross sectional area of cut, the shape of the surface also affects the forces and specific energy. Through increasing the width to depth ratio upon a constant cross sectional area of the cut, the value of the specific energy and the cutting forces are reduced. Above the width to depth ratio of 2.5 the cutting forces and the specific energy appear to be constant.
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