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... Petrological methods include Mohs scratch hardness, Rosiwal hardness, Vickers hardness, silica content, Schimazek's F value, Rock Abrasivity Index (RAI), and petrographic parameters such as quartz percentage, quartz equivalent percentage, particle size, etc. Mechanical methods comprise indentation hardness test, Cerchar abrasivity test, pin on disc test, modified Schmidt hammer test, LCPC test, and NTNU abrasion test (West 1981;Verhoef 1997;Fowell and Abu Bakar 2007;Ghasemi 2010;Labas et al. 2012). Among the test methods available for rock abrasivity measurement, the Cerchar Abrasivity Index test (Cerchar 1986;West 1989;Yarali et al. 2008;ASTM D7625 2010;Alber et al. 2014;Rostami et al. 2014;Kahraman et al. 2016) has become the most commonly used method to evaluate rock abrasiveness due to its simplicity and dependable results, especially in the tunneling industries (Plinger et al. 2004;Rostami et al. 2005;Käsling and Thuro 2010;Ko et al. 2016;Sun et al. 2019). ...
... As reported, rock mechanical properties are likely to differ due to changes in environmental fields, such as water content, temperature, and stress (Alber 2008;Majeed and Abu Bakar 2016;Abu Bakar et al. 2016). In addition, although the CAI test is commonly used, there are some reported discrepancies or variations in the test results primarily due to the variations in the testing procedure, test setup used, stylus hardness, rock surface condition, and measurement of the wear flat from the top or side of the stylus (Al Ameen and Waller 1994;Plinger et al. 2003;Fowell and Abu Bakar 2007;Stanford and Hagan 2009;Ghasemi 2010;Hamzaban et al. 2014;Rostami et al. 2014;Majeed and Abu Bakar 2016). Thus, developing good correlation between mechanical and/or geological properties and CAI values may arouse great interest of practitioners when an important TBM excavation project is planned. ...
Rock abrasivity plays an important role in the machine design, construction scheduling, and budgeting of TBM projects. Establishing several faster and simpler estimation equations for the Cerchar Abrasivity Index (CAI) of rocks is, therefore, very important. This study investigated the correlation between the CAI and mechanical properties of rock, rock mass classification parameters, and machine performance. A TBM construction database including 159 tunnel sections is established. Several acceptable and practical estimation equations of CAI are developed using simple and multiple regression analysis (0.66 < R² < 0.76). In this process, a normalized specific energy is proposed to evaluate the machine performance. The results show that the rock compressive strength and brittleness index are the most dependent parameters to explain CAI, and the estimated rock mass strength also indicates a close correlation. In addition, the contribution of a rock mass classification system and machine performance index for estimating CAI cannot be ignored. Finally, the estimation performance of the developed equations is compared and evaluated, and a new method for selecting an optimal model based on ranking is proposed. Since the input parameters of the proposed equations can be readily available at the project planning stage, they are very practical for TBM designers, tunnel designers, and contractors.
... With the improvement of the Cerchar test, several researchers have investigated the effect of test conditions. Furthermore, rock mineralogical, physical, and mechanical properties were studied on the basis of the outcomes of the Cerchar abrasivity index (CAI) (West 1989;Al-Ameen and Waller 1994;Plinninger et al. 2003;Michalakopoulos et al. 2006;Alber 2008;Altindag et al. 2010;Deliormanli 2012;Rostami et al. 2014;Yarali and Duru 2016;Ozdogan et al. 2018;Garzón-Roca et al. 2020). Zhang et al. (2020) were recently paid to consider the wear mechanism in the Cerchar test. ...
Rock abrasivity is an important parameter that influences tool design and wear, the efficiency of tools, and cost during rock excavation. Generally, the abrasiveness of rocks is measured with the Cerchar abrasivity index (CAI). In this research, several Cerchar abra-sivity parameters such as penetration of stylus (P s), the volume of material scratched in the groove (V m), scratching force (SF), scratching energy (SE), and Cerchar scratching specific energy (CSSE) were determined using an Cerchar device. For evaluating Cerchar abrasivity parameters, 24 rock samples were used comprising igneous, metamorphic, and sedimentary rocks. The new classification was presented based on the Cerchar abrasivity index and Cerchar abrasivity parameters. In this research, the specific energy of the Sievers J miniature drill test (SJ) was calculated for comparison with the specific energy of the Cerchar abrasivity test. Then, the relationship between Cerchar abrasivity parameters with SJ was investigated, new relationships between Cerchar abrasivity parameters and SJ with accurately acceptable presented. The results indicated that the Cerchar abrasion ratio (CAR) is a good parameter for measuring rock abrasivity and cutting. The SJ exhibited a good relation (R 2 = 0.78) with CAR. In addition, CAR showed a good correlation (R 2 = 0.97) with the specific energy of the rock cutting test (SE cut). The CAR can be used to evaluate abrasivity laboratory tools and the specific energy of a rock cutting test.
... Arabian Journal for Science and Engineering The independent variable is BTS (MPa) The independent variable is CAI The independent variable is GS The independent variable is SRN The Cerchar abrasivity index is universally accepted for wear prediction and estimation of cutter consumption [46,47]. Figure 7 and Eq. 4 show the relationship between the bit wear rate and the Cerchar test values for the HRC 54/56 pins with a sawn surface condition. ...
The excavation of rock, whether in mining, petroleum, or civil engineering projects, predominantly relies on traditional drilling techniques. Across these applications, drilling bit wear considered as a primary factor impacting the overall cost of rock excavation projects. This wear of drill bits is directly linked to the properties of the rock being drilled. In this study, an investigated relations between drilling bit wear and geomechanical properties have been investigated. To measure drill bit wear, a laboratory-scale drilling rig was employed, based on 30 selected rock units. A comprehensive laboratory testing plan was executed on these rock units, encompassing various rock characteristics such as uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Cerchar abrasivity index (CAI), equivalent quartz content (EQC), grain size of minerals (GS), and Schmidt rebound number (SRN). Nonlinear regression techniques were employed to predict bit wear based on geomechanical rock properties. Performance evaluation criteria were used to validate the regression models. The results revealed an exponential increase in bit wear values with rising UCS, BTS, CAI, EQC, GS, and SRN. The statistical analysis indicated a strong correlation between rock characteristics and drill bit wear, with CAI emerging as the most influential parameter, having a correlation coefficient of R2 = 0.954. The regression models developed in this study are primarily intended for rock engineers engaged in rock drilling projects.
... However, such tests do not allow an understanding of the effect of the banded structure on jaspilite abrasiveness. In contrast, the CERCHAR test [14] is a widely recommended laboratory test for assessing rock abrasiveness [15][16][17][18][19][20]. The test reflects abrasion conditions and allows the investigation of rock parameters on abrasiveness, such as grain size [16,21,22], mineralogy [15,16,21,[23][24][25], chemical composition [25,26], degree of cementation [27], and porosity [28]. ...
... Stylus wear arises from the flat diameter (in millimeters) measured with a digital microscope. Measurements can be performed from the side or top view [14,18,31]. The standard deviation of the measurements was evaluated, and no difference between the side and top views was reported. ...
Ore fragmentation is the most expensive step of mineral processing. The choice of lining materials on this type of machinery is based on ore abrasiveness. However, traditional abrasiveness tests do not consider particularities, such as the ore structure. The effect of the banded structure on jaspilite abrasiveness by conducting a CERCHAR abrasiveness test was investigated. A factorial design was applied, and the analysis included three test directions: parallel to the band of quartz minerals, parallel to the band of iron oxide minerals, and perpendicular to the bands. A hypothesis test was executed, and the difference in abrasiveness between the direction parallel to the quartz band and that parallel to the iron oxide minerals was found to be nonsignificant. However, the difference in abrasiveness between the direction parallel to the iron mineral band and the perpendicular direction was significant. Analysis of the forces monitored during the tests showed similar behavior for the different conditions. The normal load and friction force were correlated with mineral removal and characteristics of the jaspilite, such as porosity and the banding boundary. Furthermore, the observed wear mechanisms were in the transition region between mild and severe wear for all test conditions.
... The Cerchar Institute in France designed a method specific for testing rock abrasivity to solve the above problem. The method is simple and has been widely used, termed as the Cerchar test [28], the result of which, that is, Cerchar abrasivity index (CAI) value is acknowledged as an international quantitative index for evaluating the rock abrasivity. The State Key Laboratory of Shield Machine and Boring Technology in China [29] also developed a new test method for rock abrasivity. ...
The research is aimed at exploring the influences of microwave irradiation on the physicomechanical properties and Cerchar abrasivity index (CAI) of rocks. For this purpose, basalt collected in Chifeng (the Inner Mongolia Autonomous Region, China) was taken as research objects to carry out microwave irradiation tests for different durations in a multimode cavity. By using the MTS815 mechanical testing machine and the abrasion servo tester of rocks, mechanical tests and Cerchar abrasion tests were conducted before and after microwave irradiation. Changes in the mass, volume, surface fractures, surface temperature, ultrasonic wave velocity, uniaxial compressive strength (UCS), and CAI of the basalt samples before and after microwave irradiation were analyzed. Results show that the surface temperature of basalt samples linearly increases with the duration of microwave irradiation. The volume and fracture coalescence of the rock samples both increase with the prolonging duration of microwave irradiation. The mass, ultrasonic wave velocity, UCS, and CAI of the basalt samples all decrease with the increase in the duration of microwave irradiation. The reduction of the physicomechanical properties and CAI of rocks indicates that microwave irradiation can reduce the wear of rock-breaking tool and thus improve the efficiency of rock breaking.
... Another approach for the determination of rock wear is rock abrasivity index (RAI) which is the combination of mineralogical and mechanical rock parameters and is determined by multiplying the UCS value of rock material and equivalent quartz content (Plinninger 2010). The literature is rich in applications of the CAI test and interpretations of the results (Suana and Peters 1982;Al-Ameen and Waller 1994;Alber 2008;Alber et al. 2014;Rostami et al. 2014;Abu Bakar et al. 2016;Teymen 2020). ...
In this study, the usability of the wide wheel abrasion test (WA) on rock cores using a newly designed core holder apparatus is investigated. The WA test which has been proposed to determine the abrasion resistance of rocks used as natural building stones is carried out on only prismatic samples. In the design of rock engineering structures such as tunnels, dams and investigations for various purposes, samples are supplied as cylindrical cores from exploration drillings. The applicability of this test on cylindrical samples is the scope of this study. Physical and mechanical properties of nine types of rock materials are determined on these core samples in accordance with the relevant standards and suggested methods. In the context of this study, core samples with average diameters of 26.76, 39.72, 47.80, 58.16 and 67.51 mm were prepared. After that, the wide wheel abrasion tests on core samples (IA) were carried out. It is obvious that the abrasion values obtained on samples with different diameters will differ. To overcome this uncertainty applying core abrasion test on samples with 50 mm diameter is suggested and it is proposed as core abrasion index (IA-50). If needed, applicability of IA-50 test on half-cut cores (IA-HC) was also investigated, and significant linear correlation was obtained. IA-50 values were correlated with rock material parameters and significant relationships were proposed. It is believed that practical, economical, and non-destructive determination of IA-50 values will be effective to make the approach more widespread, and it will be useful in various rock engineering applications as a new parameter.
... Another approach for the determination of rock wear is Rock Abrasivity Index (RAI) which is the combination of mineralogical and mechanical rock parameters and is determined by multiplying the UCS value of rock material and equivalent quartz content (Plinninger 2010). The literature is rich in applications of the CAI test and interpretations of the results (Suana and Peters 1982;Al-Ameen and Waller 1994;Alber 2008;Alber et al. 2014;Rostami et al. 2014;Abu Bakar et al. 2016;Teymen 2020). ...
In this study, the usability of the Wide Wheel Abrasion Test (W A ) on rock cores by using a newly designed core holder apparatus is investigated. The W A test which has been proposed to determine the abrasion resistance of rocks used as natural building stones is carried out on only prismatic samples. In the design of rock engineering structures such as tunnels, dams and investigations for various purposes, samples are supplied as cylindrical cores from exploration drillings. The applicability of this test on cylindrical samples is the scope of this study. Physical and mechanical properties of nine types of rock materials are determined on these core samples in accordance with the relevant standards and suggested methods. In the context of this study, core samples with average diameters of 26.76, 39.72, 47.80, 58.16 and 67.51 mm were prepared. After that, the Wide Wheel Abrasion tests on core samples (I A ) were carried out. It is obvious that the abrasion values obtained on samples with different diameters will differ. To overcome this uncertainty applying core abrasion test on samples with 50 mm diameter is suggested and it is proposed as core abrasion index (I A−50 ). If needed, applicability of I A−50 test on half-cut cores (I A−HC ) was also investigated, and significant linear correlation was obtained. I A−50 values were correlated with rock material parameters and significant relationships were proposed. It is believed that practical, economical, and non-destructive determination of I A−50 values will be effective to make the approach more widespread, and it will be useful in various rock engineering applications as a new parameter.
... All methods require a vice clutching the sample while a toughened steel stylus with 90 cone tip is scratched over the rock surface under 70 N constant load and the scratch covers 10 mm distance. It is available in different laboratories that the Cerchar test results can not be same due to the test apparatus, measurement types and testing procedures (Rostami et al., 2014). ...
The prediction of rock cuttability to produce the lignite deposits in underground mining is important in excavation. Moreover, the certain geographic locations of rock masses for cuttability tests are also significant to apply and compare the rock cuttability parameters. In this study, sediment samples of two boreholes (Hole-1 and Hole-2) from the Sagdere Formation (Denizli Molasse Basin) were applied to find out the cerchar abrasivity index (CAI), rock quality designations (RQD), uniaxial compressive strengths, Brazilian tensile strengths and Shore hardnesses. The Sagdere Formation deposited in the terrestrial to shallow marine conditions consists mainly of conglomerates, sandstones, shales, lignites as well as reefal limestones coarse to fine grained. A dataset from the fine grained sediments (a part of the Sagdere Formation) have been created using rock parameters mentioned in the study. Dataset obtained were utilized to construct the best fitted statistical model for predicting CAI on the basis of multiple regression technique. Additionally, the relationships among the rock parameters were evaluated by fuzzy logic inference system whether the rock parameters used in the study can be correlated or not. When comparing the two statistical techniques, multiple regression method is more accurate and reliable than fuzzy logic inference method for the dataset in this study. Furthermore, CAI can be predicted by using UCS, BTS, SH and RQD values based on this study.
... Among them, abrasive wear is the most common wear form [20]. Ploughing, microcutting, microfatigue, and microcracking are main reasons for the abrasive wear [21,22]. When disc cutters roll on the tunnel face, wear loss is affected by many factors, such as properties of cutter, geological conditions, and operational conditions [23,24]. For example, on the basic of Cerchar test, Michalakopoulos et al. [25] investigated the effect of steel hardness on Cerchar Abrasivity Index (CAI), which represents the abrasiveness of rocks. ...
Argillization is a process in which clay-bearing rocks disintegrate into the clay under the action of high temperature, pressure, and water. When tunnel boring machines (TBMs) excavate in the mudstone, argillization takes place, causing the clogging of the TBM cutterhead. As a result, the penetration rate drops gradually. Abnormal wear might occur. To investigate the evolution of argillization of mudstone and cutter wear during the TBM tunnelling, a series of rotary indentation tests were carried out on the self-designed experimental bench for different loading times. During the test, the temperature and penetration depth of disc cutters were measured in real time. After loading, microstructures of cutting grooves, slacking mudstone, and worn cutter ring were observed by stereomicroscope. Consequently, the evolution of argillization in mudstone and cutter wear were investigated. Experimental results indicate that the argillization process of mudstone by disc cutter can be divided into three stages: mechanical cutting stage, deterioration of mudstone and the formation of slacking mudstone stage, and adherence of slacking mudstone stage. Specifically, at mechanical cutting stage, the rock was cut by cutter directly, causing high frictional heat. Then the microstructure of mudstone was deteriorated due to the water-weakening mechanisms, temperature effect, and mechanical activation effect. Finally, the slacking mudstone was adhered to the disc cutter. Correspondingly, due to the argillization of mudstone, the disc cutter wear goes through the mechanical wear stage, argillization wear stage, and secondary wear stage in sequence. This investigation reveals the rock cutting mechanism of TBM considering the argillization of mudstone. Furthermore, it provides some references for design and operation of the TBM.
... The CERCHAR Abrasivity Index (CAI) Test involves a stylus scratching a rock specimen for 10mm, to measure the tip wear (Fig. 7d). This test was selected to measure rock abrasivity, due to its worldwide usage and acceptance for estimation of cutter consumption (Rostami et al. 2014;Bilgin et al. 2014). CAI is an input parameter for some performance prediction models and provides an estimate of the rate of cutter replacement. ...
... With the exception of one test specimen, where saw-cut surfaces were used, this was then corrected for according to give CAI'. The side view method was used since Rostami et al. (2014) found this reduces the operator effect on the test, compared with the top view method. Four measurements were taken of each pin and a mean taken (excluding erroneous results) following the example in Alber et al. (2014). ...
... The abrasivity of all the specimens is 'low' to 'extremely low', comparable with typical values for limestone 1-3, mudstone 1-2 and shale 0.5-1.5 (Bilgin et al. 2014). Rostami et al. (2014) suggests the CAI test may not be suitable for very soft Table 6 Ground type definition and descriptions rock where there is little to no wear on the stylus; such as the mudstone/shales in this study. Additionally, during tests the tip penetrated the mudstone. ...
A major challenge that TBM performance is requested to deal with for a successful and effective progress is tunnelling through lithologically and geomechanically heterogeneous rock masses. Such heterogeneous environments are common and recent tunnel examples in the UK include the Hinckley Point C offshore cooling tunnels being driven through interbedded carbonaceous mudstone/shales and argillaceous limestone and the Anglo American’s Woodsmith Mine Mineral Transport System tunnel in Redcar Mudstone with beds of ironstone. This inherent geological heterogeneity leads to difficult tunnelling conditions that initially stem from predicting a sound and representative ground model that can be used to preliminary assess the TBM performance. In this work, an exhaustive review of existing TBM Penetration Rate (PR) methods identified that no models address the issue of parameter selection for heterogeneous rock masses comprising layers with different rock strengths. Consequently, new approaches are required for estimating rock mass behaviour and machine performance in such environments. In the presented work the Blue Lias Formation (BLI), which is characterised by its layered rock mass, comprising very strong limestone, interbedded with weak mudstone and shales, is investigated. BLI formation is considered herein being a representative example of lithological heterogeneity. Based on the fieldwork carried out in three localities in the Bristol Channel Basin (S. Wales and Somerset), geological models are produced based on which a geotechnical model is developed, and four ground types are determined. Implications of the current findings for TBM performance are assessed, including faulting, groundwater inflow and excavation stability with a particular focus on both PR and advance rate. A modified approach using the existing empirical models is proposed, developed and presented in this paper that can be used as a guide to determine TBM performance in heterogeneous rock masses reducing the risk of cost and time overruns.
