Brazilian Testing Research Articles

Unravelling the genomic characteristics of a Klebsiella quasipneumoniae clinical isolate carrying blaNDM-1

ObjectiveDespite the increasing reports of blaNDM in Enterobacterales in Brazil, comprehensive whole genome sequencing (WGS) data remain scarce. To address this knowledge gap, our study focuses on the characterization of the genome of an New Delhi Metallo-β-lactamase (NDM)-1-producing Klebsiella quasipneumoniae subsp. quasipneumoniae (KQPN) clinical strain isolated in Brazil. MethodsThe antimicrobial susceptibility profile of the A-73.113 strain was performed by agar dilution or broth microdilution following the Brazilian Antimicrobial Susceptibility Testing Committee/European Committee on Antimicrobial Susceptibility Testing recommendations. WGS was performed using the Illumina® NextSeq platform and the generated reads were assembled using the SPAdes software. The sequences obtained were submitted to the bioinformatics pipelines to determine the sequence type, resistome, plasmidome, and virulome. ResultsThe A-73.113 strain was identified as KQPN and was susceptible to polymyxins (MICs, ≤0.25 µg/mL), tigecycline (MIC, 0.5 µg/mL), ciprofloxacin (MIC, 0.5 µg/mL), and levofloxacin (MIC, 1 µg/mL). WGS analysis revealed the presence of genes conferring resistance to β-lactams (blaNDM-1, blaCTX-M-15, blaOXA-9, blaOKP-A-5, blaTEM-1), aminoglycosides [aph(3′)-VI, aadA1, aac(6′)-Ib], and fluoroquinolones (oqxAB, qnrS1, aac(6′)-Ib-cr]. Additionally, the presence of the plasmid replicons Col(pHAD28), IncFIA(HI1), IncFIB(K) (pCAV1099-114), IncFIB(pQil), and IncFII(K), as well as virulence-encoding genes fimABCDEFGHIK (type 1 fimbria), pilW (type IV pili), iutA (aerobactin), entABCDEFS/fepABCDG/fes (Ent siderophores), iroE (salmochelin), and allABCDRS (allantoin utilization) was verified. Furthermore, we found that the A-73.113 strain belongs to ST1040. ConclusionsHere we report the genomic characteristics of an NDM-1-producing KQPN ST1040 strain isolated from blood cultures in Brazil. These data will enhance our comprehension of how this species contributes to the acquisition and dissemination of blaNDM-1 in Brazilian nosocomial settings.

Experimental investigation of physical and tensile mechanical properties of granite after different heating and cooling treatments

In this study a series of physical properties of granite were tested after different cooling treatments. Correspondingly, Brazilian splitting testing combined with acoustic emission (AE) testing was conducted on five groups of granite samples at different temperature levels, and scanning electron microscopy (SEM) was used to investigate the microstructure of granite. It was found that the P-wave velocity, hardness and thermal conductivity decreased with rising temperature. The tensile strength of granite was deteriorated by the action of temperature, and the progression of cracks was monitored using AE technology. The SEM results also indicated a significant increase in both the number and density of cracks in granite samples subjected to temperature variations compared to a naturally cooled group. In addition, after heating and cooling at different temperatures, samples with lower tensile strength exhibited rougher fracture surfaces, which were attributed to the generation of more thermal cracks during the heating and cooling processes. Moreover, a variation in the mechanisms for granite after temperature treatment is proposed.

Study of the Dynamic Failure Characteristics of Anisotropic Shales Under Impact Brazilian Splitting

The mechanical behaviors of shales with transversely isotropic characteristics under dynamic loading have great significance for structural instability in geotechnical engineering. To understand the effect of transverse isotropy on the deformability and tensile strength of shales subjected to dynamic loading, a group of impact Brazilian tests were carried out on shale specimens via a split Hopkinson pressure bar (SHPB) testing system. High-speed digital image correlation technology was applied to monitor the fracture process. The experimental results demonstrate that the failure strength has considerable anisotropy as the bedding angle of the embedded layers changes. Moreover, the tensile strength of shales with vertical bedding is usually higher than that of shales with parallel bedding. The observed failure mode is mainly the interaction between tensile and/or shear fractures, and with increasing loading rate, layer-activated fractures tend to occur. Furthermore, five typical failure patterns of transversely isotropic shales characterized by different mechanisms under dynamic Brazilian testing were found. The shales were sensitive to the strain rate when the deformation and fracture response under dynamic loading were assessed. In addition, the modified Nova‒Zaninetti criterion that considers the strain rate effect was proposed according to the Brazilian splitting data and dynamic coordinate system. The established criterion not only properly represents the law of dynamic strength but also provides a new understanding of the effect of strain rate on strength. It has proven to be effective for predicting the dynamic strength characteristics of shales.

Statistical evaluation of the mechanical and flux trapping properties of standard and thin‐wall EuBCO(Ag) bulk superconductors

AbstractThe mechanical and flux trapping properties of 19 EuBCO(Ag) and 20 thin‐wall EuBCO(Ag) bulk superconductors were investigated statistically and compared to those observed for YBCO using Brazilian testing and high‐field magnetization. The average trapped fields of EuBCO(Ag) and thin‐wall EuBCO(Ag) bulk superconductors were significantly higher than those of YBCO bulk samples at 77 K measured under similar experimental conditions. However, due to the wide range of trapped field data for both materials, a statistical overlap was observed between the highest trapped fields observed for YBCO and the lowest values observed for EuBCO(Ag) bulk superconductors. All EuBCO(Ag) bulk materials measured in this study exhibit a superior tensile strength compared to YBCO bulk single grains. Unlike the case of YBCO, however, the introduction of artificial holes to EuBCO(Ag) bulk superconductors prior to melt processing was observed to decrease the average tensile strength of the single grain. Surprisingly, despite their superior mechanical and flux pinning properties, EuBCO(Ag) bulk superconductors do not exhibit enhanced performance when exposed to high fields at low temperatures.

The Impact of Axial Load Distribution on Brazilian Tensile Testing on Rock

The Impact of Axial Load Distribution on Brazilian Tensile Testing on Rock

Rate-dependence of the compressive and tensile strength of granites

Abstract. The strength and rupture of geomaterials are integral to subsurface engineering practices, such as those required to optimise geothermal energy extraction. Of particular importance is the time- and strain-rate-dependence of material strength, which dictates the energy released upon failure, and impacts the magnitude of induced seismicity, fracture architecture and thus hydraulic conductivity and system permeability. Here, we performed a series of uniaxial compression and Brazilian tensile strength measurements at a range of deformation rates in order to constrain the impact of strain rate on the strength of G603 granite. The dense, low permeability, medium-grained granites were mechanically tested at 4 strain rates (or diametric equivalent strain rates in the case of Brazilian tests) from 10−5 to 10−2 s−1, such that sample failure was achieved in anything from below 1s at the fastest rate in tension, to over 1000s at the slowest rate in compression. The applied rates encompassed those recommended by ISRM and ASTM material testing standards for compressive and Brazilian tensile testing. We found a significant rate strengthening effect, whereby compressive and tensile strength both increased by approximately 35 % across the 4 orders of magnitude of strain rate tested. We found that the static Young's modulus remained relatively constant across this range of deformation rates, however variability was reduced at faster rates, owing to the reduced time for equilibration of the system to imposed stresses. The lower strength at slower strain rates causes smaller stress drops, indicating that rocks driven to compressive and tensile failure at slower rates release less energy upon failure. Such constraints of the strain-rate-dependence of material strength, in contrast to the use of standardised material characteristics conventionally used in Engineering Geology applications, will prove useful as we develop increasingly sophisticated strategies such as cyclic soft stimulation to access resources using less energy, whilst reducing environmental risk and producing less waste.

Generation and validation of a classification model to diagnose familial hypercholesterolaemia in adults

Background and aimsThe early diagnosis of familial hypercholesterolaemia is associated with a significant reduction in cardiovascular disease (CVD) risk. While the recent use of statistical and machine learning algorithms has shown promising results in comparison with traditional clinical criteria, when applied to screening of potential FH cases in large cohorts, most studies in this field are developed using a single cohort of patients, which may hamper the application of such algorithms to other populations. In the current study, a logistic regression (LR) based algorithm was developed combining observations from three different national FH cohorts, from Portugal, Brazil and Sweden. Independent samples from these cohorts were then used to test the model, as well as an external dataset from Italy. MethodsThe area under the receiver operating characteristics (AUROC) and precision-recall (AUPRC) curves was used to assess the discriminatory ability among the different samples. Comparisons between the LR model and Dutch Lipid Clinic Network (DLCN) clinical criteria were performed by means of McNemar tests, and by the calculation of several operating characteristics. ResultsAUROC and AUPRC values were generally higher for all testing sets when compared to the training set. Compared with DLCN criteria, a significantly higher number of correctly classified observations were identified for the Brazilian (p < 0.01), Swedish (p < 0.01), and Italian testing sets (p < 0.01). Higher accuracy (Acc), G mean and F1 score values were also observed for all testing sets. ConclusionsCompared to DLCN criteria, the LR model revealed improved ability to correctly classify observations, and was able to retain a similar number of FH cases, with less false positive retention. Generalization of the LR model was very good across all testing samples, suggesting it can be an effective screening tool if applied to different populations.

Numerical investigation of ice plate fractures upon rigid ball impact

The fracture process and breaking capability of ice cover impacted by high-speed projectiles before underwater explosion is an urgent subject of scientific research in ice engineering applications. This paper presents the results of numerical simulations of the dynamic fracture behaviour induced by the impact of a small spherical projectile on an ice plate. The proposed 3D rate-dependent peridynamics model is validated by the dynamic ring Brazilian disc testing of ice specimens. Good agreements between the present model and the previous experiments are obtained in ice breaking processes and damage patterns of thin, medium and thick ice plates. Several cases are analysed and discussed in terms of various impact velocities, ice thicknesses, and boundary constraint conditions. The simulations identify detailed fracturing characteristics that are not observed in experiments, including the sequence and shape of crack propagation in a short time interval, the crater formation and the damage evolution along the thickness direction. The proposed peridynamics computational model provides new understanding of the potential of using penetrator–ice block impact tests to observe the evolution of complex brittle damage and reveal the failure mechanism.

Brazilian splitting testing of the restorative properties of eco-friendly epoxy resin on cracked granite samples with various widths

Tensile strength is a crucial mechanical property of rock. Various mass ratios kCE curing agent to eco-friendly epoxy resin are used to repair fractured rock masses by considering kSCA(mass concentrations of SCA) for rock surface treatment. To address the issue of asymmetry in bi-material samples, a novel stress-balanced sample (SRSBD) is proposed for conducting Brazilian splitting tests to evaluate the tensile behavior of repaired granite. The initiation and propagation characteristics of cracks in intact and repaired samples with different repair material thicknesses are investigated using AE and digital DIC techniques. At the minimum bonding thickness, the tensile strength (at 28 d and 42 d) is approximately 11.45 MPa with a strength recovery rate of 83.58%; however, the energy absorption is 1.28 times that of the intact rock, indicating improved ductility characteristics. For UPC, the repair effect is only 4.25 MPa at 42 d. As the epoxy thickness increases, the tensile strain proportionally increases. The tensile strength initially rises and then declines, reaching a maximum of 12.78 MPa with a 1 mm-repair. Moreover, DIC indicates that the tensile strain of the epoxy-repaired sample surpasses that of the intact specimen; while AE displays a postponed ringing onset and a reduction in early-stage frequency. Changes in kCE and the kSCA have minimal impact on the tensile repair effect, with damage primarily originating from the rock side rather than the repair material. This finding demonstrates that the eco-friendly epoxy-repaired material has a clear advantage over UPC, providing a favorable repair effect for establishing sufficient bond strength and ensuring stability in underground engineering projects.

Statistical evaluation of the mechanical properties of partially oxygenated YBCO, oxygenated YBCO and oxygenated YBCO(Ag) single grains

It is of great significance to enhance the mechanical properties in single grain YBCO bulk superconductors, as mechanical failure limits the suitability of these materials for high-field applications. The influence of the microstructure on the mechanical properties of YBCO bulk materials was studied in 11 partially oxygenated YBCO, 11 oxygenated YBCO, and 10 oxygenated YBCO(Ag) melt-processed bulk single grains in a statistically significant way using Brazilian testing. Surprisingly, the oxygenation cracks evolving during the tetragonal to orthorhombic phase transition do not influence the average tensile strength of YBCO bulk single grains, with compaction cracks and pores as the main microstructural flaws responsible for mechanical failure. The mechanical properties of bulk YBCO single grains even improve following oxygenation, as indicated by an increase in Weibull modulus. An addition of 10 wt% Ag2O to YBCO increases the average tensile strength and the Weibull modulus further, making the material mechanically more robust. However, an overlap in the measured tensile strengths of oxygenated YBCO and oxygenated YBCO(Ag) bulk materials reveals that not all silver-containing samples have better mechanical properties compared to oxygenated YBCO bulk samples.

Characterizing the cracking process of various rock types under Brazilian loading based on coupled Acoustic Emission and high-speed imaging techniques

Tensile strength is one of the important mechanical properties of rock and rock-like materials and its accurate estimation and understanding of its failure mechanism are crucial for efficient design of structures on or within the rock masses. Amongst various approaches developed for estimating this property, Brazilian testing has received considerable attention analytically, numerically and experimentally. The test has been deployed for a wide range of materials such as rock, concrete, and ceramic, however its fracturing process at micro and macro scales has not yet been properly characterized. Thus, in this study, for a full understanding of the fracturing process of different rock types under indirect tensile loading, the coupled Acoustic Emission (AE) and high-speed imaging techniques were used to characterize the generated micro and macrocracks under Brazilian loading. The characteristics of AE parameters and the evolution of micro-macro cracks were investigated for three different rocks including sandstone, coal and granite at different sizes and loading configurations. A systematic framework was developed to exhibit the link between micro and macro fracturing processes under Brazilian loading. It was noted that the tensile microcracks are the first to initiate during the Brazilian failure with high intensity compared to shear microcracks. Transition in microcracking mechanism from tension to shear was evident in the samples with high brittleness. The tensile microcracks showed ascending trends with a decrease in geometrical or volumetric sample size for granite and sandstone, while its trend for coal was inconclusive due to its unique intrinsic fracture network or so-called “cleat network”. At macro scale level, single and multiple cracking mechanisms were observed in the tested samples where those with high shear microcracks mostly revealed failure under multiple cracking. Finally, some insights were provided into the transition from single tensile cracking to multiple tensile/shear cracking based on high-speed image data with high resolution.

Quasi-static and dynamic Brazilian testing and failure analysis of a deer antler in the transverse to the osteon growth direction

The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at quasi-static and high strain rates. Dynamic Brazilian tests were performed in a compression Split-Hopkinson Pressure Bar. Quasi-static tensile and indirect Brazilian tests were also performed along the osteon growth direction for comparison. The quasi-static transverse tensile strength ranged 31.5–44.5 MPa. The strength increased to 83 MPa on the average in the dynamic Brazilian tests, proving a rate sensitive transverse strength. The quasi-static tensile strength in the osteon growth direction was however found comparably higher, 192 MPa. A Weibull analysis indicated a higher tensile ductility in the osteon growth direction than in the transverse to the osteon growth direction. The microscopic analysis of the quasi-static Brazilian test specimens (tensile strain along the osteon growth direction) revealed a micro-cracking mechanism operating by the crack deflection/twisting at the lacunae in the concentric lamellae region and at the interface between concentric lamellae and interstitial lamellae. On the other side, the specimens in the transverse direction fractured in a more brittle manner by the separation/delamination of the concentric lamellae and pulling of the interstitial lamellae. The detected increase in the transverse strength in the high strain rate tests was further ascribed to the pull and fracture of the visco-plastic collagen fibers in the interstitial lamellae. This was also confirmed microscopically; the dynamically tested specimens exhibited flatter fracture surfaces.

Common Features of Deformation Behavior Between Human Tooth Enamel and Rocks

The contribution of bioorganic components in the deformation behavior of a rock-like biocomposite human tooth enamel is discussed. Uniaxial compression testing and Brazilian testing (diametral compression) in liquid nitrogen (77 K) and in air at room temperature were carried out on the samples cut from human tooth enamel. It was compared with deformation behavior of some rocks (granite, serpentinite, and jasper) and plasma-sprayed Al2O3 under compression and Brazilian testing in air at room temperature. It was shown that enamel and the rocks exhibit the viscoelastic-like deformation behavior under compression, whereas their macroscopic response becomes brittle under tensile stress. Fracture surface morphology was attested as brittle in all model materials, although cracks in them all advance by the viscoelastic-like manner as a crack in a ductile metal. The contribution of viscoelastic bioorganic component in deformation behavior of enamel is detected at room temperature only because bioorganic component leaves the viscoelasticity at low temperatures. However, this contribution does not lead to changing the character of deformation behavior of the rock-like biocomposite in comparison with these rocks.

Some Features of Cleavage Cracks in Rocks and Metals

The cracking of some rocks, namely granite, serpentinite and sandstone under tensile stress is examined in details. Brazilian testing or diametral compression, three points bending and explosion testing are used as the loading schemes in air at room temperature. Morphology of cracks in the model rocks are compared with cracks in silicon crystals, as the standard of a brittle crack, with cleavage cracks in iridium single crystals and with cracks in gallium-covered aluminum single crystals. The comparison of cracks between themselves has shown that there is additional channel for stress accommodation in the model rocks. This channel does not lead to transformation of a rock into a macroscopically ductile material, but it causes the arrest of the dangerous crack in it under tensile stress. Its influence causes transition from the brittle crack to the pore-like crack on the microscopic scale. The most probable mechanism of this transition is the dislocation emission from crack, which becomes possible in such a natural covalent solid as a rock due to Rehbinder's effect.

Tensile strength of anisotropic rocks from enhanced Brazilian laboratory testing and data analysis protocols

The tensile strength of rock and rock-like materials is a critical material property in rock engineering design and the prediction of rockmass behaviour to mitigate any potential failure that may affect personnel safety or damage property. This study presents new instrumentation guidelines to the Brazilian Tensile Strength (splitting tensile strength) test to enhance the data processing techniques to determine true tensile strength. For this study a total of eighteen (18) specimens of two lithologies (Pointe Du Bois tonalite gneiss and Key Anacon metabasalt) were instrumented, tested, and reviewed to determine the true tensile strength of the material. This paper also identifies three potential failure modes and presents a failure envelope based on the identified potential failure modes.

Expansive Soil Stabilization by Bagasse Ash in Partial Replacement of Cement

This study examined the effects of using bagasse ash in replacement of ordinary Portland cement (OPC) in the treatment of expansive soils. The study concentrated on the compaction characteristics, volume change, compressive strength, splitting tensile strength, microstructure, California bearing ratio (CBR) value, and shear wave velocity of expansive soils treated with cement. Different bagasse ash replacement ratios were used to create soil samples. At varying curing times of 7, 14, and 28 days, standard compaction tests, unconfined compressive strength tests, CBR tests, Brazilian split tensile testing, and bender element (BE) tests were carried out. According to X-ray diffraction (XRD) investigations, quartz and crystobalite make up the majority of the minerals in bagasse ash. Bagasse ash contains a variety of grain sizes, including numerous fiber-shaped particles, according to a scanning electronic microscope (SEM) test. For all of the treated specimens with various replacement ratios, the overall additive content has not changed. The results of the Brazilian split tensile tests demonstrate improved tensile strength for all specimens with various replacement proportions. A lower maximum dry density and a greater optimal water content would result from the substitution of bagasse ash. When the replacement ratio is not more than 20%, the CBR values of the parts replaced specimens are even higher than the cement treatments. The results of BE testing on the treated soils show that there is significant stiffness anisotropy but that it steadily diminishes with curing time and replacement ratio. According to the study, bagasse ash is a useful mineral additive, and the best replacement ratio (CBA20) is 20%.

Fracturing and AE characteristics of matrix-inclusion rock types under dynamic Brazilian testing

The fracturing properties and acoustic characteristics of heterogeneous and matrix-inclusion rocks are crucial to the safety of underground infrastructures and mining projects under extreme loading conditions. In this study, elliptically shaped matrix-inclusion specimens were fabricated with cement as the matrix and three rock materials (basalt, marble and sandstone) as inclusions which cover igneous, metamorphic and sedimentary rocks with different strength ratios to the cement. Dynamic Brazilian tests were conducted on the specimens with various inclusion orientations β (i.e. angles between impact direction and inclusion major axis) in the range of 0° and 90° using a split Hopkinson pressure bar (SHPB). By combining digital image correlation (DIC) and acoustic emission (AE) techniques, the integrated system demonstrates well-synchronised dynamic forces, DIC strain fields, and AE signals. The detailed procedures were presented to interpret dynamic mechanical properties, fracturing process and AE characteristics of specimens. Generally, for stronger inclusion materials with higher stiffness and strength, dynamic peak forces, threshold orientation angles of transgranular cracks, and AE counts and duration indicate higher characteristics. For instance, the fracture pattern of basalt inclusions transforms from interfacial crack to transgranular crack with increasing orientation angle β, and the specimens with transgranular cracks exhibit higher dynamic peak forces. It is observed that transgranular cracks are mainly induced by tensile stress with a higher AE peak frequency (200–250 kHz), whereas interfacial cracks contain additional shear cracking having a relatively lower peak frequency (100–150 kHz). Meanwhile, finite element modelling demonstrates that stress fields are affected by the elastic mismatch between inclusion and matrix, while failure modes (i.e. interfacial and transgranular cracks) are mainly governed by the tensile strength of inclusions.

Rice Husk Ash as Pore Former and Reinforcement on the Porosity, Microstructure, and Tensile Strength of Aluminum MMC Fabricated via the Powder Metallurgy Method

The handling of rice husk ash (RHA) has been raising environmental concerns, which led to the consideration of incorporating RHA in aluminum metal matrix composite fabrication. Due to the high silicon dioxide content of RHA, it can assist in enhancing both the properties and functionality of pure aluminum. In this research, the fabrication of aluminum metal matrix composite was carried out by utilizing different compositions of RHA, including weight fractions of 10 wt.%, 15 wt.%, and 20 wt.% via a powder metallurgy approach. The element powders, including aluminum and RHA, and magnesium stearate as a binder, were mixed, compacted, and sintered to attain a composite sample in the form of a pellet. The pellet was then characterized using field emission scanning electron microscopy (FESEM-EDX) to identify the pore structure and size for each RHA composition. The samples were also mechanically tested via Archimedes’ Principle and Brazilian Testing to identify their density, porosity, and tensile strength, respectively. The total porosity of RHA-15 wt.% was found to be the highest at 19.19%, yet with the highest tensile strength at 5.19 MPa due to its low open porosity at 4.65%. In contrast, the total porosity of RHA-20 wt.% was found to be slightly lower at 15.38%, with the highest open porosity at 6.95%, which reduced its tensile strength to 5.10 MPa, therefore indicating that reducing open porosity through controlling the composition of reinforcement tends to enhance the mechanical strength of aluminum metal matrix composites.

Numerical modelling of the response of cemented paste backfill under the blasting of an adjacent ore stope

An in-depth understanding of the response of backfilled stopes during the blast excavation of adjacent ore stopes is crucial for the effective backfill design to improve workplace safety and ore recovery. In this study, numerical simulations are performed to explore the effects of blasting schemes and ratios of cement to tailings (c/t) on the responses of cemented paste backfilled stopes under blasting in adjacent ore stopes. Three-dimensional models comprised of ore stope, backfilled stope, explosive charge, and air were numerically established. The ore stope and backfilled stope were discretised by finite elements, while explosive charge and air were explicitly modelled using a particle-based approach. Three blasting schemes, including detonating the blastholes simultaneously, detonating the blastholes row-by-row, and detonating the blastholes column-by-column, were carried out in the ore stope, and four c/t ratios, i.e., 1:4, 1:6, 1:8, and 1:10, were used in the backfilled stope. The versatile Karagozian and Case concrete (KCC) constitutive model was used to describe the mechanical behaviour of ore and backfill materials. Its input parameters for cemented paste backfill samples with different c/t ratios were calibrated based on the uniaxial compression and Brazilian tensile testing results. The numerical results show that the row-by-row, column-by-column, and simultaneous blasting scenarios produce a similar breaking performance in the ore stope, but the latter induces the minimum damage volume in the backfilled stope. The damage generated in the backfilled stope induced by the blasting excavation in the ore stope decreases as the c/t ratio decreases. It is also found that the layered backfill structure lowers the cement cost and improves the blast resistance, and its damage tends to concentrate in the layers with higher c/t ratios. The results obtained here highlight the importance of the ductile behaviour of cemented paste backfill in the blasting resistance performance of backfilled stopes.

Prediction of Mode-I rock fracture toughness using support vector regression with metaheuristic optimization algorithms

In this work, the support vector regression method is combined with six metaheuristic optimization models of particle swarm optimization, grey wolf optimization, multiverse optimization, moth flame optimization, sine cosine algorithm, and social spider optimization to predict Mode-I rock fracture toughness. In addition, four other models of random regression forest, extra regression tree, decision regression tree, and fully-connected neural network that previously were used to predict the Mode-I rock fracture toughness by other researchers, was applied by this study. 250 datasets, including six input parameters and one output parameter (Mode-I rock fracture toughness) were utilized in the models obtained through the cracked Chevron notched Brazilian disc testing specimens suggested by the ISRM in the laboratory. Finally, the hybrid model of support vector regression-particle swarm optimization produced the most accurate results and it was recommended to predict the Mode-I rock fracture toughness. Also, the mutual information test was used to examine the impact of each input parameter on the Mode-I rock fracture toughness. Finally, the uniaxial tensile strength was identified as the most effective parameter on the Mode-I rock fracture toughness.