Rock Abrasion Research Articles

Cerchar Abrasivity Index Estimation of Andesitic Rocks in Ecuador from Petrographical Properties Using Artificial Neural Networks

Abstract Rock abrasivity is the main factor that causes erosion of excavation tools and is usually quantified by the Cerchar Abrasivity Index (CAI). Although Cerchar abrasivity tests are easy to pe...

The usability of Cerchar abrasivity index for the estimation of mechanical rock properties

One of the most commonly used methods of determining the rock abrasivity is Cerchar Abrasiveness Index (CAI). The basic parameters affecting abrasiveness are density, cementation degree, strength properties and the number of abrasive minerals in the rock. In this study, 20 different tests were carried out on 80 different rocks, mainly Young's modulus (E), uniaxial compressive strength (UCS) and CAI. The main aim of the study is to estimate the basic mechanical rock properties which are difficult to determine and time-consuming with the help of CAI values. In addition to simple equations, multiple regression equations were developed using CAI and other test methods (11 tests). Among the obtained equations, the most reliable ones were determined with the help of a developed performance index (PIat1). The results of the study show that there are significant relationships between basic mechanical rock properties and CAI.

Study of Cerchar abrasive parameters and their relations to intrinsic properties of rocks for construction

The Cerchar test method and its index, the so-called Cerchar abrasivity index, are most commonly used to determine the abrasivity of rocks and other geo-materials for construction. Recently, with the aid of a new test device, various abrasive parameters can be obtained from the Cerchar test. In this article, several abrasive parameters such as scratching force, scratching energy and scratching specific energy are determined using a special instrumented West apparatus. Three typical rock materials for construction (granite, sandstone and slate) are selected to study the correlation of Cerchar abrasive parameters with rock intrinsic properties. The research results show that the Cerchar abrasion ratio is a meaningful parameter to quantify not only the rock abrasivity, but also the rock-stylus interaction, as well as the stylus wear and the scratching effectivity.

Investigation of scratching specific energy in the Cerchar abrasivity test and its application for evaluating rock-tool interaction and efficiency of rock cutting

Wear occurs on mechanical tools during rock cutting and drilling, or any other kind of mechanical based excavation of rocks. The determination of rock abrasivity plays therefore a key role for estimating the tool's lifetime and for evaluating the economic efficiency. Due to simple design and convenient handling, the Cerchar abrasivity test is commonly used to assess the rock abrasivity and to predict the tool wear. However, the abrasivity index reflects only the abrasion of the stylus, and does not consider what happens on the tested rocks, as well as on how the stylus interacts with the rock during the scratching process. In this paper, an instrumented West apparatus is used to determine the applied horizontal force in the Cerchar test. The area under the force-displacement curve represents the consumed scratching energy. The material removed from the rock surface is measured using a digital microscope. Then, a new parameter called Cerchar specific energy, which is defined as the ratio of scratching energy to material removal volume, is proposed to assess the rock abrasivity, to describe the rock-stylus interaction, as well as to evaluate the efficiency of rock scratching, which can be used as indicator for rock cutting or drilling efficiency.

Abrasiveness evaluation of selected river gravels of Pakistan using LCPC rock abrasivity test

Abrasivity of rock and soil causes tool wear in excavation or drilling operations, and the presence of sandy gravels stratum also plays a significant role in causing serious damage to the cutting tools. Understanding the wear mechanism is important for the cost estimation and planning of projects. Abrasivity of cobbles and boulders present within soil matrix may vary from negligible in some cases to severe under certain conditions depending upon the volume and characteristics of those cobbles and boulders being encountered. Several methods have been proposed to assess the abrasivity of rock. In the present research, LCPC rock abrasivity tests were performed on 14 gravel samples collected from different river deposits of Pakistan. Practical extensions to the standard LCPC abrasivity test were used and fraction larger than 6.3 mm was incorporated in accordance with the method proposed by Thuro et al. (2007). Moreover, in order to observe the effect of increasing grain size on LCPC abrasivity coefficient (LAC g/t), 3 river gravel samples (out of initially selected 14 samples) were chosen and evaluated along with the computation of brittleness coefficient (LBC, %). Correlations were developed with LAC values of originally rounded grains against crushed/angular grains. XRD analysis was incorporated in order to determine the mineralogical composition of each sample and the possible correlation of LAC (g/t) with abrasive mineral content (AMC, %) for both modes of testing (rounded and crushed samples) were developed. Moreover, the correlations of LAC (g/t) with quartz content, equivalent quartz content, and mass-weighted average Moh’s hardness were also discussed.

THE EFFECT OF GEOLOGICAL PROPERTIES OF DIMENSION STONES ON THE PREDICTION OF SPECIFIC ENERGY (SE) DURING DIAMOND WIRE CUTTING OPERATIONS

Given the increasing demand for dimension stones, mining operations in quarries have always been an important branch of mining engineering. Among different techniques, diamond wire cutting is one of the most common methods of dimension stone mining. A reliable assessment and accurate prediction of diamond wire cutting performance are essential for feasibility analysis and operational planning in this area. This performance depends on factors such as physical, mechanical, and textural properties of the rock and the characteristics of cutting operations which can be evaluated by criteria such as specific energy, production rate, efficiency, and diamond bead wear rate. This study aims to develop a method for predicting the specific energy of diamond wire cutting in dimension stones based on rock properties. For this purpose, the specific energy of diamond wire cutting in 11 different igneous rock samples was measured. Given the high strength and abrasivity of igneous rocks, cutting operations in these rocks generally requires a great amount of energy. In a series of tests performed on the samples, rock properties such as uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Young’s modulus, density, textural properties, abrasivity and operating factors such as pullback amperage were measured. The measured parameters were divided into four groups of physical, mechanical, textural, and operating parameters. After determining the specific cutting energy of each sample, the relationship of the energy with each individual property was investigated. This investigation showed that density, abrasivity, and p-wave velocity respectively had the highest correlation with specific energy. Using the correlation results, four input parameters (one from each of the four considered parameter groups) were selected for inclusion in the prediction model. These parameters were density, abrasivity, wave velocity, and amperage. Multivariate linear regression was then used to analyse the effect of rock properties and operating parameters on specific energy. The developed regression model showed that once the rock properties are known, the specific energy can be predicted with an accuracy of 85.8%. The proposed model can be used to estimate the specific energy of diamond wire cutting operations in dimension stone quarries in advance, and predict the amount of energy consumption, the required energy source, and the optimal cutting machine accordingly.

On effect of surface hardening on impact and abrasive wear resistance of Hadfi eld steel

On the example of Hadfield steel, as the most common material of fast-wearing parts of mining equipment, the effect of surface hardening by plastic deformation on their impact and abrasive wear resistance is considered. Wear test is conducted on magnetic ironstone as typical representative of abrasive and hard rock. As result of wear of initial samples with hardness of ∼200 HB and samples pre-hardened with different intensities to the hardness of 300, 337 and 368 HB, it is found that during the initial testing period, the initial samples pass the “self-cold-work hardening” stage with increase in hardness to ∼250 HB, which remains virtually unchanged during further tests; the hardness of the pre-hardened samples does not change significantly throughout the tests. It is established that the rate of impact-abrasive wear of pre-hardened samples is significantly (up to 1.4 times) lower than the original ones that are not subjected to plastic deformation, and decreases with increasing degree of cold-work hardening. Preliminary surface hardening by plastic deformation can serve as effective way to increase the service life of fast-wearing working parts of mining equipment.

Estimation of uniaxial compressive strength of very low-medium abrasive rocks from Cerchar abrasiveness index

Estimation of uniaxial compressive strength of very low-medium abrasive rocks from Cerchar abrasiveness index

Comparative analysis cutting characteristics of stinger PDC cutter and conventional PDC cutter

The Stinger PDC cutter has a better performance than the conventional PDC cutter drilling for hard, interbedded and highly abrasive rocks. Although researchers have investigated the cutter's characteristic, such as impact resistance, wear resistance and cutter's life, the cutting behaviors of the Stinger PDC cutter still remains unclear. In this study, the single cutter tests were carried out with a Stinger PDC cutter and a conventional PDC cutter as comparisons. The cutting force, cuttings size, surface topography along the cutting trajectory and microscopic morphology of the fracture surface were compared and analyzed. The results show that the average cutting force of a Stinger PDC cutter is 46.14% lower than that of a conventional PDC cutter. The proportion of large cuttings (r > 2.36 mm) generated in the Stinger PDC cutter test is higher than that in the conventional PDC cutter test. In addition, the energy consumption of breaking rocks by a Stinger PDC cutter is 34.09% lower than that by a conventional PDC cutter. The cutting trajectory in the Stinger PDC cutter test has a “V” shape and the surface is relatively rough (Sa = 617.08 μm), while the conventional PDC cutter produces a “U” shape cutting trajectory and the surface is relatively smooth (Sa = 462.18 μm). Furthermore, the SEM analysis shows that the Stinger PDC cutter breaks granite mainly by tensile stress, which is different with the conventional PDC cutter by shear stress. The key findings of this work will help to reveal the rock-breaking process and mechanism with the Stinger PDC cutters.

Оценка влияния абразивности горных пород на параметры породоразрушающих машин

Development of equipment, which provides access to underground mineral deposits and their extraction, requires the use of all the accumulated experience and advanced scientific research in the area of mechanical rock cutting. The most important issues of using mechanical rock cutting tools are their wearability and consumption, which have an impact on technical and economic indicators of project efficiency. The paper describes Russian and foreign practices of estimating tool wear resistance, expressions to determine critical cutting speed, methods to evaluate tool consumption. It is demonstrated that wearability of mechanical tools and associated effects are to a large extent defined by rock abrasiveness. It is highlighted that in Russia the index is calculated using Baron-Kuznetsov method, which is briefly described in the paper. In many countries with a highly-developed mining industry, rock abrasiveness is estimated with a Cerchar Abrasiveness Index (CAI), recommended by the International Society for Rock Mechanics. Its description is also presented in the paper.

The Influence of the Physical and Mechanical Properties on the Abrasion Rate of Rocks Along Idfo-Marsa Alam, Eastern Desert, Egypt

The physico-mechanical properties of rocks have crucial influence on their abrasion rates. Therefore, the objective of this study is to investigate the rock properties that govern their abrasion resistivity. For that purpose, about 132 core specimens, of granite, marble, serpentine, and breccia, were extracted from two locations in Wadi El-Miah region in the vicinity of Idfo-Mars Alam Road, South-East, Egypt. Several laboratory tests were conducted to determine the relationships between abrasion resistance and physical (i.e. porosity, density and P-wave velocity) and mechanical (i.e. uniaxial compressive strength, tensile strength and surface hardness) properties of these rocks. Subsequently, statistical analysis was employed to derive equations for estimating abrasion rates based on physico-mechanical rock properties. The results showed that the abrasion resistance decreases with increasing uniaxial compressive strength, Brazilian tensile strength, Schmidt rebound hardness, P-wave velocity, and bulk density. It was also revealed that the abrasion rate increases with increasing effective porosity. Additionally, the derived equations showed good correlations between abrasion resistance and bulk density; Schmidt rebound hardness; and tensile strength (i.e. R2 = 0.72–0.84). Thus, they can be successfully used to predict the abrasion rates. Hence, rock abrasion rate could be adopted as a tool to sort out stones for proper industrial purposes (i.e. flooring, heavy traffic, decoration, construction, building, etc.).

Development of a GEP model to assess CERCHAR abrasivity index of rocks based on geomechanical properties

The CERCHAR abrasivity test is very popular for determination of rock abrasivity. An accurate estimation of the CERCHAR abrasivity index (CAI) is useful for excavation operation costs. This paper presents a model to calculate CAI based on the gene expression programming (GEP) approach. This model is trained and tested based on a database collected from the experimental results available in the literature. The proposed GEP model predicts CAI based on two basic geomechanical properties of rocks, i.e. rock abrasivity index (RAI) and Brazilian tensile strength (BTS). Root mean square error (RMSE), mean absolute error (MAE), Nash-Sutcliffe efficiency (NSE), and coefficient of determination (R2) are used to measure the model performance. Furthermore, the developed GEP model is compared with linear and non-linear multiple regression and other existing models in the literature. The results obtained show that GEP is a strong technique for the prediction of CAI.

The new method for assessing rock abrasivity in terms of wear of conical picks

Abstract During the exploitation of mineral raw materials, a cutting tool is an element that is directly in contact with the unmined stone being cut. The most commonly used cutting tools include conical picks. The increasing pressure to reduce mining costs causes an increasing demand for affordable and reliable ways to increase the reliability of mining machines. Abrasive wear is the most common process affecting the wear of shearer picks, hence a good and simple laboratory method for assessing rocks abrasivity is needed. The new method was developed in the aspect of selection of conical picks with appropriate protection of the pick working part, increasing its durability. The method involves the assessment of mass abrasive wear of a standard steel pin and rock sample, and the determination of the abrasivity index Wz of the tested rock, as the ratio of the mass loss of the steel pin to the mass loss of the rock sample. The article presents the procedure of conducting tests, construction of a laboratory test stand and the use of the developed method to assess the abrasivity of gangue rocks occurring in the currently cut tunnel excavations of Polish hard coal mines.

Abrasivity evaluation for wear prediction of button drill bits using geotechnical rock properties

The current study investigates the wear life of button bits and rate of penetration (ROP) of rotary-percussive drilling machines by employing geotechnical rock properties. According to the research plan, three hydropower projects and six active mining quarries in Pakistan were included. The field work included recording of drill bit consumption (m/bit) and measurement of penetration rate (m/min) from the 11 selected rock units. A comprehensive laboratory testing plan on the collected rock units was carried out to include rock abrasivity assessment [CERCHAR (CAI), LCPC (ABR) and abrasion value steel (AVS) tests], NTNU/SINTEF drillability parameters [Sievers’ J-value (SJ), brittleness value (S20), Cutter Life Index™ (CLI) and Drilling Rate Index™ (DRI)] and physico-mechanical properties [uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), porosity (n), density (ρ), p wave velocity (Vp), Schmidt rebound hardness (SRH) and brittleness index (B3)]. Moreover, XRD analyses were performed to compute equivalent quartz content (EQC %), rock abrasivity index (RAI) and Vickers hardness number of rock (VHNR). The least square regression technique was employed to predict bit life from geotechnical rock properties. Dependence of ROP on geotechnical rock parameters was also discussed. Finally, two multiple linear regression models were also proposed for the estimation of bit life based on the included geotechnical rock properties. The developed multi-variable models were validated using the F-test statistical method. The correlations so developed are particularly proposed for rock engineers involved in rock drilling projects.

Assessing Effectiveness of Various Wear-Resistant Materials Used as Hard Facings in Mining Applications

Characterizing the abrasiveness of soil/rock and the allowable wear of hard-facing products in various conditions is a critical factor in selection of the best material for certain applications related to drilling and excavation in mining and construction industries. The Soil Abrasion Index test machine at Colorado School of Mines (CSM) is one of the recently developed unique systems capable of testing soil/crushed rock abrasion under various conditions, such as dry, wet, and saturated settings. It is also capable of testing the performance of various types of hard-facing materials in a given geo-material. This paper studies the wear properties of different hard-facing materials in various crushed rocks from a surface mining operation in the iron range region of the USA. The hard-facing materials include regular and hardened steels and six different specialized hard facings, based on chromium carbide. The soil/rock include a standard sand and two rock samples from the surface mine. Fourteen abrasion tests were conducted, where the weight loss of each hard-facing material was measured over timespans up to 1 h of testing. The results show the distinct performance differences between the steels with 17 HRC and 43 HRC hardness and the hard-facing products for this application. The results show the possibility to evaluate the abrasiveness of different rocks at a mine or construction site and the performance of various hard facings in similar working conditions. This is a practical solution for selection of the cutting tool or reinforcement of bucket lips and truck beds for comparison of relative wear life between different wear-resistant materials.

Introduction to Rock and Soil Abrasivity Index (RSAI)

Characterizing the abrasiveness of rock and soil and developing predictive models for wear of various tools that interact with such geo-materials is critical in selection of best tool materials for applications in earthmoving, drilling, mining, construction, tunneling, and agricultural industries. This paper introduces a Rock and Soil Abrasivity Index (RSAI), utilizes the abrasive wear theory for defining the parameters and examines a testing method for quantitative assessment of the index. The test method measures the wear mass of a target tool material (i.e. steel or hard facing) while it is pressed against the crushed rock or soil medium in a relative motion under high contact stresses based on a defined test protocol for reliability and repeatability. The RSAI is defined as the product of wear volume and hardness of tool divided by the work or energy deployed to overcome frictional forces, as measured by the torque in the device. The RSAI is expected to vary in the 0–100 range for the softest to the hardest possible rock and soil samples and conditions. The RSAI for various soil and crushed rock samples were experimentally determined and presented. Also, the correlation between the RSAI, Cerchar Abrasion Index (CAI) and Soil Abrasion Test (SAT) value, as the most common forms of abrasion testing of soil and rock is discussed.

Mass destruction of strong rocks by intermittent emissions of hydro charges

Several thousand of small gold and rare-metal deposits are located at a depth inaccessible for open mining in underdeveloped areas of Kazakhstan, which in their limited reserves are either classified as off-balance or are not included in the register of reserves of the SRC (State Reserves Committee). This article discusses the creation and the development of new technologies that are based on the use of fundamentally new technical means will be effective and able to reduce the cost of mining. The hydro-impulse method of rocks destruction of any fortress is offered that will allow reducing sharply the scopes of capital and actual mining at a considerable decrease in their Prime cost. Therefore, it will be possible to involve in the effective development of numerous off-balance gold and rare-metal deposits of Kazakhstan. For this purpose, a comparative analysis of the economic and technical efficiency of the hydro-impulse destruction of strong and abrasive rocks in the ore industry with respect to the existing drilling and blasting technology is given, the developed design of an environmentally friendly electric-discharge hydro-impulse gun GPE-1200 with a very high power of hydrofoil is described. The specific recommended design mechanisms, shut-off valves water gun, operating at ultrahigh hydrostatic intra assembly unit pressures, which include how to combine the blasting of the rock mass in the excavation or clearing operations and use the device for drilling wells.

Physical characterization and alkali carbonate reactivity (ACR) potential of the rocks from Bauhti Pind and Bajar area Hassan Abdal, Pakistan

This study is conducted to evaluate aggregate characteristics and alkali carbonate reactivity (ACR) potential of carbonate rocks of the Bouhti Pind and Bajar area, Hassan Abdal, Pakistan. Physical and chemical tests were performed to assess aggregate suitability. Mean specific gravity (2.65–2.65), water absorption (0.51–0.68%), Los Angeles abrasion (24.78–26.10%) and sulphate soundness values (2.86–4.25%) of the carbonate rocks of these areas are within specified limits of their respective standards. Petrographic studies of Bajar area reveal the presence of 96.3% calcite, 2% clays, 1% hematite and 0.7% quartz. These rocks do not contain dolomite and show no expansion in rock cylinder test. Therefore, the aggregate is not prone to ACR and can be used in cement concrete. Rocks of Bouhti Pind area have mean 92% calcite, 3.8% dolomite, 2% clays, 1.2% hematite and 1% monocrystalline quartz. The amount of deleterious minerals specifically dolomite and clays are below the maximum allowed limit to initiate ACR. However, one of the rock cylinders shows 0.043% expansion which is below threshold limit of 0.10% to cause ACR as specified in ASTM C-585. Hence, these carbonate rocks qualify physical characterization and ACR tests and can be used in the construction of roads and in cement concrete.

Aeolian abrasion of rocks as a mechanism to produce methane in the Martian atmosphere

Seasonal changes in methane background levels and methane spikes have been detected in situ a metre above the Martian surface, and larger methane plumes detected via ground-based remote sensing, however their origin have not yet been adequately explained. Proposed methane sources include the UV irradiation of meteoritic-derived organic matter, hydrothermal reactions with olivine, organic breakdown via meteoroid impact, release from gas hydrates, biological production, or the release of methane from fluid inclusions in basalt during aeolian erosion. Here we quantify for the first time the potential importance of aeolian abrasion as a mechanism for releasing trapped methane from within rocks, by coupling estimates of present day surface wind abrasion with the methane contents of a variety of Martian meteorites, analogue terrestrial basalts and analogue terrestrial sedimentary rocks. We demonstrate that the abrasion of basalt under present day Martian rates of aeolian erosion is highly unlikely to produce detectable changes in methane concentrations in the atmosphere. We further show that, although there is a greater potential for methane production from the aeolian abrasion of certain sedimentary rocks, to produce the magnitude of methane concentrations analysed by the Curiosity rover they would have to contain methane in similar concentrations as economic reserved of biogenic/thermogenic deposits on Earth. Therefore we suggest that aeolian abrasion is an unlikely origin of the methane detected in the Martian atmosphere, and that other methane sources are required.

Abrasiveness evaluation of rock\u2013cone bit based on fractured cuttings

This paper looks at the influence of the sorting coefficient, average particle size and quartz content on the abrasion rate of the cone bit. This paper uses rock drillability experiments, particle sizing tests and XRD mineral component analyses as methodology. The results show that the larger the average particle size and sorting coefficient, the smaller the real contact area between the bit and the rock surface, the smaller the friction force. Meanwhile, the volume of the fractured cuttings increased. The results also show that the less the quartz content, the less hard points in the rock. All these factors lead to the reduction in drill bit damage. Because of the strong correlation among the factors of abrasiveness, this paper develops a model of the drill bit abrasion using the partial least square method. The main factors of the model are the grain size distribution and the quartz content of the rock. This model can also be used in the selection of drill bit type and the classification of rock abrasion.