Rock abrasivity, as one of the most important parameters affecting the rock drillability, significantly influences the drilling rate in mines. Therefore, rock abrasivity should be carefully evaluated prior to selecting and employing drilling machines. Since the tests for a rock abrasivity assessment require sophisticated laboratory equipment, empirical models can be used to predict rock abrasivity. Several indices based on five known methods have been introduced for assessing rock abrasivity including rock abrasivity index (RAI), Cerchar abrasivity index (CAI), Schimazek’ s abrasivity factor (Fabrasivity), bit wear index (BWI), and LCPC abrasivity coefficient (LAC). In this work, 12 rock types with different origins were investigated using the uniaxial compressive strength (UCS), Brazilian test for tensile strength, and longitudinal wave velocity and LCPC tests, and microscopic observations were made to obtain a correlation for estimating the LCPC abrasivity coefficient by conducting the conventional rock mechanics tests. Using the equivalent quartz content, velocity of longitudinal waves, and rock brittleness index, a linear correlation was obtained with a coefficient of determination (R2) of 93. 3% using SPSS in order to estimate LAC.

Abrasivity, as one of the most important parameters has great influence on drilling rate. Up to now, four known methods such as "Rock Abrasiveness Index (RAI)", "Cerchar Abrasiveness Index (CAI)", "Schimazek's wear factor (F-abrasivity)" and "Bit Wear Index (BWI)" have been developed for evaluating of rock abrasivity. In this paper, abrasivity of six rock types has been studied using Schimazek's wear factor and Rock Abrasiveness Index. For this purpose, equivalent quartz content and the mean size of rock grains have been calculated using thin section of rocks. All types of rocks have been tested view pointed of compressive and tensile strength (Brazilian test) in laboratory. For evaluating of drillability of rocks, the samples have been drilled using actual percussive-rotary drilling machine. Results reveal that by increasing Schmazek's wear factor, drilling rate decreases logarithmically and by increasing Rock Abrasiveness Index, drilling rate decreases exponentially.

Introduction: Up to now, various indexes and methods have been presented for evaluating the abrasivity of rocks. In total, these methods can be divided to two main groups; the methods based on nature of rocks, methods based on heuristic tools. Schimazek F-abrasivity index is one of the most powerful and applicable indexes for evaluating the rock abrasiveness. This index uses the grain size, Brazilian tensile strength and equivalent quartz content for abrasivity analysis. Since the values of these parameters are equal in Schimazek index, therefore, in some cases this index doesn't have suitable ability to distinguish and classify the rock abrasiveness. This paper tries to modify the Schimazek index considering the weights of its applied parameters.

This study investigates the geomechanical properties of sandstone from the southern part of Isfahan city using the Cerchar Abrasivity Index (CAI), Unconfined Compressive Strength (UCS), and point load tests. Twelve sandstone samples were analyzed to evaluate their abrasiveness and mechanical strength. The CAI value was determined to be 3. 55, indicating a moderately high level of abrasiveness. The UCS test revealed strength of 35 MPa, and the estimated Hardness Rating (HR) was 25. 6. These findings offer critical insights into the material properties of Isfahan’s sandstone, which are essential for construction and excavation projects in the region. The results provide a useful framework for predicting tool wear and rock behavior during engineering operations.

LCPC test is one of the most common methods to assess the abrasivity of rock particles and soil samples. Regarding the lack of a standard testing procedure to determine the abrasivity of soils, the test has become very popular in recent decades. The effect of clay on soil abrasivity was investigated with LCPC tests. Different mixtures of crushed silica grains and clay particles were used in the testing program. Moreover, measuring the consumed power of the electric motor of the testing device, the consumed energy of each LCPC test was calculated. Different moisture contents and stress levels were also applied in the tests. The results showed that the LCPC abrasivity coefficient decreases with increasing moisture content. However, after a certain water content level, abrasivity shows an increasing trend with moisture. abrasivity is nearly zero in pure clay samples. The results showed that minimum abrasivity values are obtained when the moisture content is in the range between plastic limit and liquid limit. Applied stress on the soil samples, increases the soil abrasivity. However, increasing the clay content of the tested samples decreases the rate of LAC increasing trends with the applied stress levels. In the pure clay samples, no correlation was obtained between the applied stress levels and LAC values. The results showed that the clay part alone does not have a sensible abrasivity. However, its mixtures with coarse grains have a considerable effect on the abrasive behavior of tested samples especially when the applied water contents and stress levels change.

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.

One of the most critical problems of mechanized tunnelling is the abrasion of cutting tools. Soil abrasivity significantly reduces drilling efficiency and increases the operating costs of urban tunnels. There are extensive studies on abrasivity of rocks. However, limited studies have been performed on the influence of soil particle size distribution on tunnelling machine cutting tools. Despite the wide range of methods and devices for measuring soil abrasivity, so far, no standard and comprehensive method for measuring soil abrasivity have been presented. In this study, considering the effect of some effective parameters on the abrasion of cutting tools, a new laboratory machine to determine soil abrasivity was constructed. Then, using 8 different types of soil granulation, the effect of soil particle size distribution and density on cutting tool abrasion was studied. Also, using the Talbot curve, the abrasion values ​​of cutting tools in different particle sizes were compared. The results showed that the highest values ​​of cutting tools abrasion occur in soils with particle sizes according to the Talbot equation. As the soil granulation curve moves away from the Talbot curve, abrasivity decreases. Also, the maximum abrasion of cutting tools occurs in the amount of fine aggregate of 10% with an average abrasion percentage of 27.3%. By reducing the fine aggregate to values lower than 10%, the soil structure is disturbed and as a result, the average abrasion percentage of cutting tools decreases from 27.3% in soil with 10% fine aggregate to 2.37% in soil without fine aggregate. Also, by increasing soil density from 1.6 to 1.8, the average abrasion percentage of cutting tools increases from 8.1% to 31.4%.

One of the tests that is used for the characterization of soil abrasivity, is LCPC test. LCPC test device is designed for measuring the wear particles as small as pebbles (4-6.3 mm). In this study, some of the most important abrasive minerals were collected from different parts of Iran for analyzing the effect of the geological parameters on the ability of abrasive minerals. Firstly, amount of index minerals abrasivity is measured according to three standards of AFNOR P18-553, AFNOR P18-579 and AFNOR P18-560 that are the preparation of samples for testing, procedure of laboratory tests and analysis of grain size with laboratory sieves. The effect of geological parameters affecting the wear rate of the sample, including five parameters of shape, size, angularity and saturation rate of the environment, has been studied. The effectiveness of these parameters on the abrasivity of samples are studied according to NF ISO 5725 relating to usage of statistics, the accuracy of test method, the repeatability and the ability to reproduce a standard way of testing within laboratory (based on classification index X 06-041). Finally, after ensuring significant effect of these parameters on the abrasivity of minerals by help of SPSS, abrasivity rates for types of minerals that have the hardness below 7 in the Mohs hardness scale, have been predicted.

Increasing demand for the application of mechanical excavation techniques in various civil and mining projects has increased the importance of ground abrasive properties and their mechanized excavatability. The accurate prognosis of cutting tools lifetime has crucial importance in the planning of mechanized tunneling projects. Moreover, the precise estimation of the required cutter number for excavating the determined length of a given section in a specific geotechnical condition is one of the main tasks of the project consultants. The main objective of these estimations is to assess the needed time and cost of cutter replacements in the phase of feasibility studies and to plan a proper maintenance schedule. The LCPC testing procedure is one of the simplest and most common soil abrasivity assessment methods. The purpose of the presented study is to investigate the steel– soil interaction during the LCPC abrasion test. The consumed energy of LCPC tests on different abrasive samples was measured. Based on the recorded energy values, a new parameter of wear-specific energy of the LCPC test (WSEL) was introduced. The obtained WSEL values showed meaningful correlations with the sample grains size and the sample average hardness. Moreover, the results revealed that the high LCPC abrasion coefficient (LAC) values are relevant to the high consumed energy levels recorded during the tests.