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1
Gao, Min, Zhengzhao Liang, Shanpo Jia, and Jiuqun Zou. "Tensile Properties and Tensile Failure Criteria of Layered Rocks." Applied Sciences 12, no. 12 (June 15, 2022): 6063. http://dx.doi.org/10.3390/app12126063.
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Rocks are less resistant to tension than to compression or shear. Tension cracks commonly initiate compression or shear failure. The mechanical behavior of layered rocks under compression has been studied extensively, whereas the tensile behavior still remains uncertain. In this paper, we study the effect of layer orientation on the strength and failure patterns of layered rocks under direct and indirect tension through experimental and numerical testing (RFPA2D: numerical software of Rock Failure Process Analysis). The results suggest that the dip angle of the bedding planes significantly affects the tensile strength, failure patterns, and progressive deformation of layered rocks. The failure modes of the layered specimens indicate that the tensile strength obtained by the Brazilian disc test is not as accurate as that obtained by the direct tension test. Therefore, the modified Single Plane of Weakness (MSPW) failure criterion is proposed to predict the tensile strength of the layered rocks based on the failure modes of direct tension. The analytical predictions of the MSPW failure criterion agrees closely with the experimental and numerical results. In rock engineering, the MSPW failure criterion can conveniently predict the tensile strength and reflect the failure modes of layered rocks (such as shale, slate, and layered sandstone) with satisfactory accuracy.
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Mohammed, Ahmed, and Wael Mahmood. "Statistical Variations and New Correlation Models to Predict the Mechanical Behavior and Ultimate Shear Strength of Gypsum Rock." Open Engineering 8, no. 1 (August 11, 2018): 213–26. http://dx.doi.org/10.1515/eng-2018-0026.
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Abstract In this study, over 1000 data from the several research studies was used to characterize and compare the density, strengths, modulus, flexural strength, porosity and the ultimate shear strengths of the calcium rocks. The gypsum rock data were statistically analyzed, quantified and compared with the limestone rock data. The ranges of the densities for gypsum rock (CaSO4·2H2O) and limestone rock (CaCO3) were 2.10 to 2.83 gm/cm3 and 1.70 to 2.75 gm/cm3, respectively. The compressive and tensile strengths of the gypsum and limestone rocks varied from 2 MPa to 250 MPa and 1.8 MPa to 25 MPa, respectively. Vipulanandan correlation model was effective in relating the modulus of elasticity, flexural strength, with the relevant strengths of the rocks. A new nonlinear Vipulanandan failure criterion was developed to better quantify the tensile strength, pure shear (cohesion) strength and predict the maximum shear strength limit with applied normal stress on the gypsum and limestone rocks. The prediction of the failure models for the two rock types was also compared to the Mohr-Coulomb failure model. The Vipulanandan failure model predicted the maximum shear strength limit was, as the Mohr-Coulomb failure model does not have a limit on the maximum shear strength. With the Vipulanandan failure model based on the available data, the maximum shear strengths predicted for the gypsum and limestone rocks were 64 MPa and 114 MPa, respectively.
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Nath, Fatick, Peter E. Salvati, Mehdi Mokhtari, Abdennour Seibi, and Asadollah Hayatdavoudi. "Laboratory Investigation of Dynamic Strain Development in Sandstone and Carbonate Rocks Under Diametrical Compression Using Digital-Image Correlation." SPE Journal 24, no. 01 (November 29, 2018): 254–73. http://dx.doi.org/10.2118/187515-pa.
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Summary Understanding the mechanical behavior (compression, shear, or tension) of rocks plays an important role in wellbore-stability design and hydraulic-fracturing optimization. Among rock mechanical properties, strain is a critical parameter describing rock deformation under stress with respect to its original condition, yet conventional methods for strain measurement have several deficiencies. In this paper, we analyze the application of the optical method digital-image correlation (DIC) to provide detailed information regarding fracture patterns and dynamic strain development under Brazilian testing conditions. The effects of porosity, rock type, lamination, and saturation (freshwater and brine) on indirect tensile strength are also discussed. To examine the effect of rock type, 60 samples of sandstone (Parker, Nugget, and Berea) and carbonate rocks (Winterset Limestone, Silurian Dolomite, Edwards Brown Carbonate, and Austin Chalk) were tested under dry and saturated conditions with regard to lamination angle in laminated samples. A photogrammetry system was used to monitor the samples in a noncontact manner while conducting the indirect tensile experiment. DIC depends on the photogrammetry system, which helps to visualize and examine rock-fracture patterns from the recorded images of the rock before and after deformation by assessing the strain development in samples. The experimental results show the following. Average tensile strength declines with increasing porosity for homogeneous, laminated, and heterogeneous rock specimens. Lower tensile strengths are observed in carbonate-rock samples compared with sandstones, except for Silurian Dolomite. Saturation reduces rock strength; for homogeneous samples, the highest strength decline (28%) was observed in Berea Sandstone, whereas the largest decrease (65%) for heterogeneous samples was observed in fully heterogeneous Edwards Brown Carbonate samples. Increase of lamination angle (from 0 to 90°) affects the tensile strength. Average tensile strength observed for the Parker and Nugget Sandstones was greater in the direction perpendicular to the lamination direction (θ = 90°) compared with that of the parallel direction (θ = 0°). Fracture patterns examined for homogeneous rocks are nearly centrally propagated and relatively linear. Three different fracture patterns (central fracture, layer activation, and noncentral or mixed mode) were investigated for laminated and heterogeneous samples. Finally, DIC results illustrated the fracture creation and propagation with consistent strain mapping. The homogeneous samples produced a uniform fracture strain until the diametrical split, where the laminated samples were influenced by planes of weakness and fully heterogeneous anisotropic rocks produced winding and erratic fractures.
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Mohammadabadi, Behzad Jafari, Kourosh Shahriar, Hossein Jalalifar, and Kaveh Ahangari. "AN INVESTIGATION ON THE EFFECTS OF MICRO-PARAMETERS ON THE STRENGTH PROPERTIES OF ROCK." Rudarsko-geološko-naftni zbornik 36, no. 1 (2021): 111–19. http://dx.doi.org/10.17794/rgn.2021.1.9.
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Rocks are formed from particles and the interaction between those particles controls the behaviour of a rock’s mechanical properties. Since it is very important to conduct extensive studies about the relationship between the micro-parameters and macro-parameters of rock, this paper investigates the effects of some micro-parameters on strength properties and the behaviour of cracks in rock. This is carried out by using numerical simulation of an extensive series of Uniaxial Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests. The micro-parameters included the particles’ contact modulus, the contact stiff ness ratio, bond cohesion, bond tensile strength, the friction coefficient and the friction angle, and the mechanical properties of chromite rock have been considered as base values of the investigation. Based on the obtained results, it was found that the most important micro-parameters on the behaviour of rock in the compressive state are bond cohesion, bond tensile strength, and the friction coefficient. Also, the bond tensile strength showed the largest effect under tensile conditions. The micro-parameter of bond tensile strength increased the rock tensile strength (up to 5 times), minimized destructive cracks and increased the corresponding strain (almost 2.5 times) during critical stress.
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Mohammed, Diyari A., and Younis M. Alshkane. "Tensile Strength Modeling of Limestone Rocks in Sulaymaniyah City, Iraq Using Simple Tests." Polytechnic Journal 9, no. 2 (December 1, 2019): 149–55. http://dx.doi.org/10.25156/ptj.v9n2y2019.pp149-155.
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Tensile strength of rocks is one of the mechanical properties of intact rock that is a significant parameter for designing geotechnical structures includes dam foundations and tunnels. The tensile strength can be determined indirectly using Brazilian indirect test procedure that is mentioned in the International Society for Rock Mechanics suggested methods. The availability of rock samples is needed to perform the Brazilian indirect test so as to determine their tensile strength which is expensive, time-consuming, and cost-effective especially for weak quality rock formations. Therefore, non-destructive methods for predicting the tensile strength of the rock are crucially needed during the poor quality of rock samples. Non-destructive tests can be correlated with indirect tests to predict Brazilian tensile strength (BTS) of rocks such as ultrasonic pulse velocity and Schmidt hammer. These methods are simple and can be easily conducted in the field. This study is focused on the tensile strength of limestone rocks for three main formations of Sulaymaniyah city. The samples were obtained using a standard core barrel. Statistical analysis including minimum, maximum, mean, standard deviation, variance, and coefficient of variance for the results was conducted. Single and multiple correlations between BTS and each of ultrasonic pulse velocity and Schmidt hammer rebound number of limestone rocks were created. Reasonable empirical equations were developed to predict the tensile strength of limestone rocks. In addition, the point load strength index was correlated with BTS. The comparison between proposed equations from this study and equation from the literature was also investigated.
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Huang, Zhengjun, Ying Zhang, Yuan Li, Dong Zhang, Tong Yang, and Zhili Sui. "Determining Tensile Strength of Rock by the Direct Tensile, Brazilian Splitting, and Three-Point Bending Methods: A Comparative Study." Advances in Civil Engineering 2021 (June 2, 2021): 1–16. http://dx.doi.org/10.1155/2021/5519230.
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To accurately obtain the tensile strength of rock and fully understand the evolution process of rock failure is one of the key issues to the research of rock mechanics theories and rock mass engineering applications. Using direct tensile, Brazilian splitting, and three-point bending test methods, we performed indoor and numerical simulation experiments on marble, granite, and diabase and investigated the tensile strength and damage evolution process of several typical rocks in the three different tests. Our experiments demonstrate that (1) the strength is about 10% greater in the Brazilian splitting than in the direct tensile, while the tensile modulus is lower; it is the highest in the three-point bending, which is actually subjected to the bending moment and suggested as one of the indexes to evaluate the tensile strength of rock; (2) the strength in splitting tests is strikingly different, while the strain law is basically similar; the direct tensile test with precut slits is more attainable than that with no-cut slits, with an uninfluenced strength; (3) the failure modes of rocks using different methods are featured by different lithology, while their final modes are basically the same under the same method; (4) PFC and RFPA numerical simulation tests are effective to analyze the internal crack multiplication and acoustic emission changes in the rock as well as the damage evolution process of rock in different tests.
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Yao, Wei, Kaiwen Xia, and Ajay Kumar Jha. "Experimental study of dynamic bending failure of Laurentian granite: loading rate and pre-load effects." Canadian Geotechnical Journal 56, no. 2 (February 2019): 228–35. http://dx.doi.org/10.1139/cgj-2017-0707.
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In deep underground rock engineering projects, rocks are under static pre-load and they may further experience dynamic load due to earthquakes or production blasts. It is thus desirable to consider dynamic failure of rocks subjected to static pre-load. Besides, bending load is commonly encountered near underground openings. Therefore, this study considers the effect of the pre-load on the dynamic bending strength of Laurentian granite (LG). Using a modified split Hopkinson pressure bar system, the semi-circular bend (SCB) method is applied to carry out the bending tests. Five groups of SCB specimens are tested under different pre-loads and loading rates. The results show that under a given pre-load, the flexural tensile strength of LG increases with the loading rate, and decreases with the static pre-load at a given loading rate. The total flexural tensile strength is roughly independent of the pre-load. An empirical equation is used to represent the effects of the loading rate and the pre-load force on the dynamic flexural tensile strength. Furthermore, the flexural tensile strengths measured from SCB tests have higher values than the tensile strengths measured using the Brazilian disc method for the same rock. A nonlocal failure theory is utilized to quantitatively interpret this discrepancy.
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Muñiz-Menéndez, Mauro, and Ignacio Pérez-Rey. "Intact rock deformation bimodularity: an experimental study." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012041. http://dx.doi.org/10.1088/1755-1315/1124/1/012041.
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Abstract Rock deformability under tensile stresses plays an important role in different scenarios like, e.g., in the mechanical behaviour of roofs in underground openings, hydraulic fracturing, dilatometer tests performed in massive rock masses or in tensile strength tests. Different authors have proved that the tensile deformation modulus of the intact rock can be significantly different than that obtained under compressive load, being this so-called ‘bimodularity’ often ignored. In this work, we present preliminary results from uniaxial compressive and tensile strength tests carried out in three rocks with a testing apparatus recently modified to be able to perform both types of tests. Experimental results show that the deformational behaviour of the rocks studied is dependent on the type of load applied. The present work aims at contributing to a better understanding of the deformational behaviour of rocks, in particular when subjected to uniaxial tensile loads as well as in dealing with future updates of existing test methodologies.
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Tomiczek, K. "A study of rock response to failure in the context of the bending properties and comparison with uniaxial tensile and compression behaviour." IOP Conference Series: Earth and Environmental Science 1049, no. 1 (June 1, 2022): 012010. http://dx.doi.org/10.1088/1755-1315/1049/1/012010.
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Abstract The phenomenon of rock bending occurs during underground exploitation, construction of underground excavations and tunnels, and even rising heading – shafts. It is also common in building engineering, e.g., in the case of floors. Rocks and concretes as granular materials on the aggregate scale are fractured as a result of exceeding shear and tensile strength. In a complex state of stress – bending, crack propagation occurs from tensioned to compressed fibres. Three-point bending tests of medium-grained quasi homogeneous and isotropic sandstone were tested for strength and deformation properties of rocks. The E deformability modules for compressed and tensioned fibres as well as strains at failure were determined. The results of three-point bending were compared with the results of uniaxial compression and direct tension. Clear differences were found in the values of strengths, moduli of deformation and strains at failure. The bending strength B of about 9.5MPa is almost 3 times greater than the direct tensile strength σT of about 3.2MPa and is 1/10 of the ultimate uniaxial compression strength σC . With three-point bending, the values of the moduli E are equal to: for tensioned fibres about 6.7GPa, for compressed fibres 14.6GPa; in uniaxial compression tests about 13.0GPa and in direct tensile tests 4.8GPa. Rock material was also failure at various strains values at the ultimate strength. In the case of three-point bending tests, the strains at failure were equal to: for tensioned fibres about 0.125%, and for compressed fibres 0.065%; in uniaxial compression tests εz were equal to about 0.63% and in direct tension tests 0.07%.
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Li, Shengwei, Cunbao Li, Wei Yao, Ru Zhang, Jing Xie, Junchen Zhang, Qiang Liu, and Zhaopeng Zhang. "Impact of wetting-drying cycles on dynamic tensile strength of rock." Thermal Science 23, Suppl. 3 (2019): 815–20. http://dx.doi.org/10.2298/tsci180411115l.
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To study the effect of wetting-drying cycles on dynamic tensile strength of rock, dynamic indirect tension test of sandstone samples after 0, 1, 3, and 5 wetting-drying cycles was conducted. Tensile failure was observed by digital image correlation. The result shows that failure appears in the center of the samples initially, consistent with tensile strain field results obtained by digital image correlation. An empirical formula was derived to link loading rate and dynamic tensile strength of rock after wetting-drying cycles. As the loading rate increases, tensile strength increases significantly. Tensile strength reduces as the number of wetting-drying cycles increases. These results provide reference data for complex engineering problems such as those that occur in coal mining, tunneling and water conservancy.
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Yang, Xu-Xu, Hong-Wen Jing, and Wei-Guo Qiao. "Numerical Investigation of the Failure Mechanism of Transversely Isotropic Rocks with a Particle Flow Modeling Method." Processes 6, no. 9 (September 17, 2018): 171. http://dx.doi.org/10.3390/pr6090171.
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Transversely isotropic rocks are commonly encountered in rock engineering practices, and their strength and failure behavior is often governed by the property of anisotropy. The particle flow modeling method was utilized to investigate the failure mechanism of transversely isotropic rocks subject to uniaxial compressive loading. The details for establishing transversely isotropic rock models were first presented, and then a parametric study was carried out to look into the effect of interface properties on the failure mode and strength of transversely isotropic rock models by varying the interface dip angle. The smooth joint model was incorporated to create interfaces for the completeness of establishing transversely isotropic rock models with the particle flow modeling method. Accordingly, three failure modes observed in transversely isotropic rock models with varying dip angles were tensile failure across interfaces, shear failure along interfaces, and tensile failure along interfaces. Furthermore, the interface mechanical parameters were found to differently influence the failure behavior of transversely isotropic rock models. The bonded joint cohesion and bonded joint friction angle that contribute to the shear strength of interfaces have considerable influence on the uniaxial compressive strength (UCS) values, while the joint coefficient of friction and joint tensile strength have a slight influence on the UCS values. The findings in this paper indicated the importance of interfaces in estimating failure behavior of transversely isotropic rocks.
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Rao, Qiuhua, Zelin Liu, Chunde Ma, Wei Yi, and Weibin Xie. "A New Flattened Cylinder Specimen for Direct Tensile Test of Rock." Sensors 21, no. 12 (June 17, 2021): 4157. http://dx.doi.org/10.3390/s21124157.
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In recent decades, researchers have paid more attention to the indirect tensile test than to the direct tensile test (DTT) of rocks, mainly due to difficulties in the alignment and the stress concentration at the end of an intact cylindrical specimen. In this paper, a new flattened cylinder specimen and a clamp device were designed to obtain the true tensile strength of the rock in DTT. Stress distributions of the specimen with different lengths (l) and cutting thicknesses (t) were analyzed, and damage processes of the specimen were monitored by the Digital Image Correlation (DIC), the fractured sections were also scanned. Different mechanical parameters were also obtained by the DTT of the flattened cylinder specimens and the intact cylinder specimens, as well as the Brazilian disc. Research results show that the tensile strength obtained by DTT is smaller than the Brazilian disc and is slightly greater than the intact cylindrical specimen. The flattened cylinder specimen with 0.20 ≤ 2t/D < 0.68 and 0.10 ≤ l/D ≤ 0.20 is recommended to measure the true tensile strength of rock material in DTT. This new shape of the specimen is promising to be extended in the uniaxial or triaxial direct tension test.
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Zhang, Qunlei, Zihan Zhi, Chun Feng, Ruixia Li, Jinchao Yue, and Junyu Cong. "Using Continuum-Discontinuum Element Method to Model the Foliation-Affected Fracturing in Rock Brazilian Test." Advances in Civil Engineering 2021 (July 6, 2021): 1–9. http://dx.doi.org/10.1155/2021/1404568.
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In this study, the continuum-discontinuum element method (CDEM) was used to investigate the tensile fracture mechanism of rock materials. An isotropic rock disk model and models considering different foliation inclinations were established, and three schemes were used to simulate the rock fracturing in Brazilian test. Then, the influences of the rock matrix and foliation strengths on anisotropy rock fracturing were investigated. Furtherly, simulation results were verified, and the rock fracture mechanisms were discussed. The results show that the rock fracturing in Brazilian test can be accurately simulated by CDEM, which is in accordance with the experimental results. For isotropic and horizontal foliation rock, the stress concentration in loading positions causes a local fracture of rock sample, and application of a local strengthening scheme can simulate the integral tension fracture of sample middle. As the foliation angle varies from 15° to 45°, the rock fracturing is affected by the stress concentration and foliation distribution. In splitting simulation, a strengthening scheme should be adopted to overcome this influence. As a result, the rock sample generates the sliding and compression-shear fracture. As the foliation angle changes from 45° to 75°, the foliation, rather than the matrix, dominates the fracture behavior of rock sample. For vertical foliations’ rock, as the middle foliation thickness is appropriately broadened, the simulation results are reasonable. In general, the tensile strength of anisotropic rock entirely decreases with an increase of foliation angle, and the effect of foliation strength on the tensile strength rock sample is larger than that of the rock matrix.
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ERMOLOVICH, E. A., and A. V. OVCHINNIKOV. "INVESTIGATION OF THERMAL AND MATERIAL FIELDS INFL UENCE ON CHANGES OF PHYSICAL AND MECHANICAL CHARACTERISTICS OF CHALK FOR ASSESSMENT OF ITS WORKABILITY." News of the Tula state university. Sciences of Earth 2, no. 1 (2020): 247–63. http://dx.doi.org/10.46689/2218-5194-2020-2-1-247-263.
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Experimental studies were performed and the dependences of the influence of thermal and material fields on the change in the following physical and mechanical characteristics of the chalk were established: density, the ultimate compressive strength, ultimate tensile strength, ultimate shear strength, elastic modulus, Poisson's ratio, and stickiness. The geomechanical and energy criteria characterizing the chalk workability are calculated: the coefficient of hardness, the indicator of the difficulty of rock destruction, the indicator of the difficulty of rock excavation, the energy intensity of digging and rock destruction. A classification of chalk by workability was developed, in which 5 categories of rocks are distinguished: I -soft chalk, of very low strength; II - dense semi-solid chalk, low strength; III - solid dense chalk of increased strength; IV - solid strong chalk; V - rocky chalk
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Zhou, Lang, Zhenqian Ma, Hongfei Xie, Wei Yang, and Hanghang Zheng. "Numerical Simulation Experimental Study of the Deformation and Failure of Granite with Multiaxial Tension." Processes 10, no. 5 (May 10, 2022): 949. http://dx.doi.org/10.3390/pr10050949.
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A numerical simulation method is proposed to study the deformation and failure rule of granite with multi-directional tensile stress, based on the importance of the rock tension. This investigation took into consideration the fact that the current experimental equipment cannot complete multi-directional tension experiments for rock. The deformation and failure rule of the granite material model with biaxial and triaxial tensile stress are studied using the numerical simulation software CASRock. The results show that in a biaxial tensile stress state, the tensile strength of granite decreases with the increase in the confining pressure, but the influence of the compression confining pressure on the strength reduction is greater than the tensile confining pressure. The number of cracks generated during failure decreases with the increase in the compressive confining pressure, and the inclination angle of the failure surface increases with the increase in the compressive confining pressure. In the three-direction tension stress state, the tensile strength of granite decreases slightly with the increase in the compressive confining pressure. However, when the compressive confining pressure in one direction is close to the uniaxial tensile strength, the tensile strength of granite will decrease quickly, and the failure result is similar to that of the uniaxial tensile failure.
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Fan, Qi, Shuan Cheng Gu, Bo Nan Wang, and Rong Bin Huang. "Two-Parameter Parabolic Mohr Strength Criterion Applied to Analyze the Results of the Brazilian Test." Applied Mechanics and Materials 624 (August 2014): 630–34. http://dx.doi.org/10.4028/www.scientific.net/amm.624.630.
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Geotechnical engineering in tension damage is one of the major failure modes. For a long time, Brazil test has practical significance and wide application value that has been used to determine the tensile strength of rock. When the specimen center destroyed tensile stress play a major role that is the theoretical basis of Brazil test. This is uniaxial tensile stress state, but the reality is complex stress state. Theoretical analysis shows that the Brazilian test does not truly reflect the tensile strength of rock, its test results to error. In this paper, two-parameter parabolic Mohr strength criterion for this error analysis, and propose amendments to the formula.
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Roslan, R., RC Omar, I. N. Z. Baharuddin, Hairin Taha, M. M. Fared, and W. N. S. W. Hashim. "Determination of Segari Rock Slope Excavation Technique using Geological Strength Index (GSI)." International Journal of Engineering & Technology 7, no. 4.35 (November 30, 2018): 819. http://dx.doi.org/10.14419/ijet.v7i4.35.23114.
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Segari - Ayer Tawar rock materials were generally characterized as slightly weathered (Grade II) to moderately weathered (Grade III). Laboratory tests such as Brazilian tensile strength and point load strength index including direct shear strength were carried out using collected weathering sample from borehole to assess the rock strength. Hence, index testing was used to predict geological strength index, rock failure criterion from Hoek-Brown and deformation modulus mainly for the classification of rock mass engineering properties. The relationship between the uniaxial compressive strength and geological strength index of rocks were used in proposing suitable methods for cutting the rock slope.
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Xia, Kaiwen, Sheng Huang, and Ajay Kumar Jha. "Dynamic Tensile Test of Coal, Shale and Sandstone Using Split Hopkinson Pressure Bar." International Journal of Geotechnical Earthquake Engineering 1, no. 2 (July 2010): 24–37. http://dx.doi.org/10.4018/jgee.2010070103.
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The dynamic tensile strength plays a pivotal role in rock fragmentation affecting the overall economics under the present ‘Mine to Mill Concept’. In this paper, a modified SHPB technique and Brazilian test method is presented to test the dynamic tensile strength of coal, shale and sandstone rock samples collected from three opencast mines of Coal India Limited and is compared with the static strength value. The dynamic tensile strength of coal and rock is much higher than static strength and tensile strength of coal and rock samples increase with loading rate. The result shows that the dynamic strength of the coal sample is 1.5 times higher than static strength and the dynamic strength of the sandstone sample is 3 times higher than the static strength.
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Jónsson, Sigurjón. "Tensile rock mass strength estimated using InSAR." Geophysical Research Letters 39, no. 21 (November 2012): n/a. http://dx.doi.org/10.1029/2012gl053309.
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Vishal, V., S. P. Pradhan, and T. N. Singh. "Tensile Strength of Rock Under Elevated Temperatures." Geotechnical and Geological Engineering 29, no. 6 (September 8, 2011): 1127–33. http://dx.doi.org/10.1007/s10706-011-9440-y.
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Shu, Jiaming, Lishuai Jiang, Peng Kong, and Qingbiao Wang. "Numerical Analysis of the Mechanical Behaviors of Various Jointed Rocks under Uniaxial Tension Loading." Applied Sciences 9, no. 9 (May 1, 2019): 1824. http://dx.doi.org/10.3390/app9091824.
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In a complex stress field of underground mining or geotechnical practice, tension damage/failure in rock masses is easily triggered and dominant. Unlike metals, rocks are generally bi-modularity materials with different mechanical properties (Young’s modulus, etc.) in compression and tension. It is well established that the Young’s modulus of a rock mass is directly related to the presence of the fracture or joint, and the Young’s modulus estimation for jointed rocks and rock masses is essential for stability analysis. In this paper, the tensile properties in joint rocks were investigated by using numerical simulations based on the discrete element method. Four influencing parameters relating to the tensile properties (joint dip angle, joint spacing, joint intersection angle, and joint density) were studied. The numerical results show that there is an approximately linear relationship between the joint dip angle (α) and the joint intersection angle (β) with the tensile strength (σt), however, the changes in α and β have less influence on the Young’s modulus in tension (Et). With respect to joint spacing, the simulations show that the effects of joint spacing on σt and Et are negligible. In relation to the joint density, the numerical results reveal that the joint intensity of rock mass has great effect on Et but insignificant effect on σt.
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Wang, Tingting, Pingfeng Li, Chun’an Tang, Bingbing Zhang, Jiang Yu, and Tao Geng. "Tensile Characteristics and Fracture Mode of Frozen Fractured Rock Mass Based on Brazilian Splitting Test." Applied Sciences 12, no. 22 (November 20, 2022): 11788. http://dx.doi.org/10.3390/app122211788.
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Frozen fractured rock mass is often encountered during the implementation of geotechnical engineering in cold regions. The tensile strength parameters of frozen rock play an important role in the construction of rock slopes involving tensile failure. In order to study the tensile characteristics of a frozen fractured rock mass in a cold region, original rock specimens were mined and processed in the Yulong Copper Mine, and artificial, frozen fractured marble specimens were made. The effects of different ice-filled crack angles, lengths, and widths on the force–displacement curve and the tensile strength of frozen rock were studied by laboratory Brazilian splitting experiments and RFPA3D, and the evolution law of the tensile strength of frozen rock was revealed. At the same time, wing crack initiation and cracking mode after tensile failure were analyzed by high-speed camera; the whole process of the Brazilian splitting of frozen rock was reconstructed, and the development of microcrack initiation in frozen rock was analyzed. The following conclusions were drawn from the test results: the frozen rock specimens have typical brittle-failure characteristics. The tensile strength of frozen rock decreases gradually with the increase in the width and length of ice-filled cracks, and decreases first and then increases with the increase in the angle of the ice-filled crack. The ice-filled crack incurs damage first, and then the wing cracks start from the tip of the ice-filled crack and extend continuously. The tensile strength of frozen rock is significantly affected by the angle and length of ice-filled cracks.
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Yao, Chi, Sizhi Zeng, and Jianhua Yang. "Failure Process Simulation of Interlayered Rocks under Compression." Advances in Civil Engineering 2018 (August 1, 2018): 1–13. http://dx.doi.org/10.1155/2018/9615457.
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Anisotropy in strength and deformation of rock mass induced by bedding planes and interlayered structures is a vital problem in rock mechanics and rock engineering. The modified rigid block spring method (RBSM), initially proposed for modeling of isotropic rock, is extended to study the failure process of interlayered rocks under compression with different confining pressures. The modified rigid block spring method is used to simulate the initiation and propagation of microcracks. The Mohr–Coulomb criterion is employed to determine shear failure events and the tensile strength criterion for tensile failure events. Rock materials are replaced by an assembly of Voronoi-based polygonal blocks. To explicitly simulate structural planes and for automatic mesh generation, a multistep point insertion procedure is proposed. A typical experiment on interlayered rocks in literature is simulated using the proposed model. Effects of the orientation of bedding planes with regard to the loading direction on the failure mechanism and strength anisotropy are emphasized. Results indicate that the modified RBSM model succeeds in capturing main failure mechanisms and strength anisotropy induced by interlayered structures and different confining pressures.
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Feng, Gan, Xiao-chuan Wang, Yong Kang, Shi-gang Luo, and Yao-qing Hu. "Effects of Temperature on the Relationship between Mode-I Fracture Toughness and Tensile Strength of Rock." Applied Sciences 9, no. 7 (March 29, 2019): 1326. http://dx.doi.org/10.3390/app9071326.
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Fracture toughness is used to characterize rock resistance to fracturing and it is important in theoretical research and engineering applications. Mode-I fracture toughness can be predicted on the basis of an empirical relationship between fracture toughness (KIC) and tensile strength (σt). In underground engineering, rocks are often subjected to different temperatures. Therefore, this paper explores the effect of temperature on the relationship between mode-I fracture toughness and tensile strength. The results show that the change trends in the KIC and σt values of rocks at temperatures from 20 °C to 600 °C are broadly consistent with each other. For rocks heat-treated to the same temperature, the KIC of the rock increases with an increase in σt. This positive correlation between KIC and σt is different in rocks heat-treated to different temperatures. Critical crack propagation radius (rIC) is an important factor in the relationship between KIC and σt and is related to the type of rock and the conditions under which it is tested. For the same rock, rIC is quite different after it has been exposed to different temperatures. The positive correlation between KIC and σt results from a similarity in the fracture morphology and properties of failure when rock is destroyed in fracture and tensile tests.
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Zheng, Bowen, Shengwen Qi, Xiaolin Huang, Ning Liang, and Songfeng Guo. "Compression-Induced Tensile Mechanical Behaviors of the Crystalline Rock under Dynamic Loads." Materials 13, no. 22 (November 12, 2020): 5107. http://dx.doi.org/10.3390/ma13225107.
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Characterization of the tensile mechanical behaviors of rocks under dynamic loads is of great significance for the practical engineering. However, thus far, its micromechanics have rarely been studied. This paper micromechanically investigated the compression-induced tensile mechanical behaviors of the crystalline rock using the grain-based model (GBM) by universal distinct element code (UDEC). Results showed that the crystalline rock has the rate- and heterogeneity-dependency of tensile behaviors. Essentially, dynamic Brazilian tensile strength increased in a linear manner as the loading rate increased. With the size distribution and morphology of grain-scale heterogeneity weakened, it increased, and this trend was obviously enhanced as the loading rate increased. Additionally, the rate-dependent characteristic became strong with the grain heterogeneity weakened. The grain heterogeneity prominently affected the stress distribution inside the synthetic crystalline rock, especially in the mixed compression and tension zone. Due to heterogeneity, there were tensile stress concentrations (TSCs) in the sample which could favor microcracking and strength weakening of the sample. As the grain heterogeneity weakened or the loading rate increased, the magnitude of the TSC had a decreasing trend and there was a transition from the sharp TSC to the smooth tensile stress distribution zone. The progressive failure of the crystalline rock was notably influenced by the loading rate, which mainly represented the formation of the crushing zone adjacent to two loading points. Our results are meaningful for the practical engineering such as underground protection works from stress waves.
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Hu, Xuelong, Ming Zhang, Xiangyang Zhang, Min Tu, Zhiqiang Yin, Haifeng Ma, and Minke Duan. "A Coupled Elastoplastic Damage Dynamic Model for Rock." Shock and Vibration 2021 (October 4, 2021): 1–10. http://dx.doi.org/10.1155/2021/5567019.
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Rock dynamic constitutive model plays an important role in understanding dynamic response and addressing rock dynamic problems. Based on elastoplastic mechanics and damage mechanics, a dynamic constitutive model of rock coupled with elastoplastic damage is established. In this model, unified strength theory is taken as the yield criterion; to reflect the different damage evolution law of rocks under tension and pressure conditions, the effective plastic strain and volumetric plastic strain are used to represent the compressive damage variable and the equivalent plastic strain is used to represent the tensile damage variable; the plastic hardening behavior and strain rate effect of rocks are characterized by piecewise function and dynamic increase factor function, respectively; Fortran language and LS-DYNA User-Defined Interface (Umat) are used to numerically implement the constitutive model; the constitutive model is verified by three classical examples of rock uniaxial and triaxial compression tests, rock uniaxial tensile test, and rock ballistic test. The results show that the constitutive model can describe the dynamic and static mechanical behavior of rock comprehensively.
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Saksala, Timo. "Numerical Modeling of Temperature Effect on Tensile Strength of Granitic Rock." Applied Sciences 11, no. 10 (May 12, 2021): 4407. http://dx.doi.org/10.3390/app11104407.
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The aim of this paper is to numerically predict the temperature effect on the tensile strength of granitic rock. To this end, a numerical approach based on the embedded discontinuity finite elements is developed. The underlying thermo-mechanical problem is solved with a staggered method marching explicitly in time while using extreme mass scaling, allowed by the quasi-static nature of the slow heating of a rock sample to a uniform target temperature, to increase the critical time step. Linear triangle elements are used to implement the embedded discontinuity kinematics with two intersecting cracks in a single element. It is assumed that the quartz mineral, with its strong and anomalous temperature dependence upon approaching the α-β transition at the Curie point (~573 °C), in granitic rock is the major factor resulting in thermal cracking and the consequent degradation of tensile strength. Accordingly, only the thermal expansion coefficient of quartz depends on temperature in the present approach. Moreover, numerically, the rock is taken as isotropic except for the tensile strength, which is unique for each mineral in a rock. In the numerical simulations mimicking the experimental setup on granitic numerical rock samples consisting of quartz, feldspar and biotite minerals, the sample is first heated slowly to a target temperature below the Curie point. Then, a uniaxial tension test is numerically performed on the cooled down sample. The simulations demonstrate the validity of the proposed approach as the experimental deterioration of the tensile strength of the rock is predicted with agreeable accuracy.
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Packulak, T. R. M., J. J. Day, and M. S. Diederichs. "Tensile strength of anisotropic rocks from enhanced Brazilian laboratory testing and data analysis protocols." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012040. http://dx.doi.org/10.1088/1755-1315/1124/1/012040.
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Abstract 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.
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Efimov, V. P. "Determination of tensile strength by the measured rock bending strength." Journal of Mining Science 47, no. 5 (September 2011): 580–86. http://dx.doi.org/10.1134/s1062739147050066.
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Misa, Rafał, and Andrzej Nowakowski. "Comparison of the Compressive and Tensile Strength Values of Rocks Obtained on the Basis of Various Standards and Recommendations." Symmetry 13, no. 7 (June 28, 2021): 1163. http://dx.doi.org/10.3390/sym13071163.
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The objective of the current study was to compare results relating to the compressive and tensile strength of rocks obtained during research undertaken according to Polish Standards (as part of the European standards known as Eurocodes), American Society for Testing and Materials (ASTM) Standards, and the recommendations of the International Society for Rock Mechanics (ISRM). A total of 130 experiments for uniaxial compression on axisymmetric samples, point loads, and transverse compression (so-called Brazilian tests) were performed on rock samples comprising granite, limestone, and sandstone. Geometric properties of the samples were selected depending on the applied research method, and the relationship between the specimen’s slenderness and shape, and the obtained values of compressive and tensile strength, were analyzed. The results of the study showed that values of compressive and tensile strength obtained in a laboratory depend significantly on specimen slenderness, different values of which are imposed by various ISRM standards and recommendations, wherein this sensitivity was much higher in the case of compressive strength. The study also raised doubt about the usefulness of the so-called point load test as a method for determination of the compressive strength of rocks and potential estimation of the tensile strength.
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Gong, Fengqiang, Le Zhang, and Shanyong Wang. "Loading Rate Effect of Rock Material with the Direct Tensile and Three Brazilian Disc Tests." Advances in Civil Engineering 2019 (March 10, 2019): 1–8. http://dx.doi.org/10.1155/2019/6260351.
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A series of experimental tests were conducted to investigate the effects of loading rate on the tensile strength of sandstone by using four test methods, including a direct tensile method and three typical Brazilian disc methods (plate loading, circular arc loading, and strip loading). The loading rates used in these tests varied from 10−2 MPa/s to 100 MPa/s. The results show that the rate effects are clear for these test methods, and the tensile strength of sandstone will increase linearly with the logarithm of the loading rate. At the same loading rate, it is found that the tensile strengths of the sandstone specimens under plate loading and arc loading are relatively similar and are much greater than the direct tensile strength, while the tensile strength under strip loading is less than the direct strength. A comprehensive comparison suggested that the strip loading method can be adopted for the Brazilian disc test, while the obtained strength should be modified with a coefficient of 1.37 to obtain the direct tensile strength.
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Yan, Chun Ling, De Xin Ding, Yi Qun Tang, and Zhong Wei Bi. "Testing of Strength Parameters and Deformation Parameters of Surrounding Rock and their Distributions." Advanced Materials Research 261-263 (May 2011): 1360–64. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1360.
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Cores were taken from the hanging wall of the III -1 ore body at Kangjiawan Lead, Zinc and Gold Mine. 50 samples for compression and tension tests were fabricated. 50 compressive and 50 tensile strength values were obtained by RMT-150B testing systems. The probability distributions for the compressive and tensile strength were tested by the hypothesis test method. It proves that uniaxial compressive strength follows normal distribution and tensile strength follows the lognormal distribution. And it proves that elastic modulus and Poson’s ratio follow normal distribution. 50 pairs of cohesion and internal friction angle were obtained by randomly drawing a uniaxial compressive and tensile strength samples from 50 measured values. Cohesion follows lognormal distribution and internal friction angle follows normal distribution through hypothesis test method. With the results, some references can be conveniently provided for prediction of the strength and distribution of similar rocks in related geotechnical projects.
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Zhang, Ying Hua, Bo Chuan Zhao, Zhou Jing Ye, Zhi An Huang, and Ming Shan Gong. "Experiment Research of Luming Molybdenum Mine Rock Physical and Mechanical Properties." Advanced Materials Research 881-883 (January 2014): 1726–31. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1726.
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Physical and mechanical properties of rocks are the fundamental factors affecting the slope stability, the rock physical and mechanical properties of the Luming molybdenum mine were tested and analyzed in the laboratory. The results can provide us the basic data and reference to do numerical simulation and physical simulation of slope stability. The experimental results showed that: the greater the depth of rock of Luming molybdenum mine, the greater the density becomes,so as the freeze-thaw coefficient; the rock strength complies with the general rule; uniaxial tensile strength of dried rocks is much larger than water-saturated rocks; various rocks compressive strength σ3 rose up with σ1 rising; the shear strength of the rocks containing weak structure surface is far less than the shear strength of the intact rocks.
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Zhu, Wan Cheng, K. T. Chau, and Chun An Tang. "Numerical Simulation on Failure Patterns of Rock Discs and Rings Subject to Diametral Line Loads." Key Engineering Materials 261-263 (April 2004): 1517–22. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.1517.
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Brazilian test is a standardized test for measuring indirect tensile strength of rock and concrete disc (or cylinder). Similar test called indirect tensile test has also been used for other geomaterials. Although splitting of the disc into two halves is the expected failure mode, other rupture modes had also been observed. More importantly, the splitting tensile strength of rock can vary significantly with the specimen geometry and loading condition. In this study, a numerical code called RFPA2D (abbreviated from Rock Failure Process Analysis) is used to simulate the failure process of disc and ring specimens subject to Brazilian test. The failure patterns and splitting tensile strengths of specimens with different size and loading-strip-width are simulated and compared with existing experimental results. In addition, two distinct failure patterns observed in ring tests have been simulated using RFPA2D and thus this verifies the applicability of RFPA2D in simulating rock failure process under static loads.
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Adebayo, B., and B. Adetula. "Evaluation of physical and mechanical properties of rock for drilling condition classification." World Journal of Engineering 10, no. 4 (August 21, 2013): 359–66. http://dx.doi.org/10.1260/1708-5284.10.4.359.
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This work deals with the investigation of physical and mechanical properties of selected rocks for condition of drilling categorization. Rock samples collected from five drilling locations were tested in the laboratory for uniaxial compressive strength, tensile strength, and Drilling Rate Index (DRI) using 1,100 kN compression machine, point load tester and miniature drill. Similarly, hardness, brittleness, Rock Abrasivity Index (RAI), penetration rate and bit wear rate were determined. The results showed that uniaxial compressive strength, tensile strength and Drilling Rate Index varied from 47.78 - 111.11 MPa, 8.09 - 19.44 MPa, and 20 - 52 respectively. The Nast point system chart was used to classify the rocks into drilling conditions. The drilling classification shows that the drilling condition of the rocks varied from slow to fast. The drillability characteristics of the rocks vary from extremely low to medium as specified by the Drilling rate Index (DRI). It was concluded that uniaxial compressive strength, texture and grain size, drilling rate index and Equivalent Quartz Content (EQC) are important parameters affecting drilling condition of the rocks.
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Wang, Ru, Chun An Tang, Shu Hong Wang, Zhi Yuan Wang, and Tian Hui Ma. "Influence of Different Loading Modes on Rock Tensile Strength." Key Engineering Materials 353-358 (September 2007): 2553–56. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.2553.
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A typical mechanical character of rock is that the tensile strength is far less than the compressive strength. Meanwhile, the test data of tensile strength is very dispersive. Because the direct tensile tests always result in failure due to the difficulty in clamping the rock sample, the splitting test is used to determine the tensile strength of rock. There are four kinds of loading modes in the splitting test in actual laboratory test: angle pad splitting, round pad splitting, aclinic loading platen splitting, arc loading platen splitting. In this paper, the direct tensile test, the splitting test and the influence of different loading modes on rock tensile strength were studied. In order to study the stress distribution, the progressive splitting failure process was numerically modeled under the four kinds of loading cases by the Realistic Failure Process Analysis code (RFPA2D). Results show that the stress states under angle pad splitting, round pad splitting are similar to the stress states under diametrical compressive state. Regarding that the round pad splitting test is easy to implement, and its numerical results are also stable relatively, the round pad loading mode was suggested to be adopted.
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Yang, Xianda, Lihui Sun, Jiale Song, Bensheng Yang, Chengren Lan, and Qingfeng He. "Study on the Effect of Bond Strength on the Failure Mode of Coarse-Grained Sandstone in Weakly Cemented Stratum." Minerals 12, no. 1 (December 31, 2021): 55. http://dx.doi.org/10.3390/min12010055.
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Bond strength is one of the most important parameters and can affect the macroscopic mechanical properties and the damage state of rock to some degree. Coarse-grained sandstone was studied using the controlled variable method. The influence of parallel bond strength on the peak strength and failure mode of coarse-grained sandstone was simulated, and the evolution law of peak strength and the failure mode of bond strength were comprehensively analyzed. The results show that the peak strength of the rock was positively correlated with the bond strength; the difference in quantity between the tensile and shear cracks was negatively correlated with tensile bond strength and positively correlated with shear bond strength. With a tensile-shear bond strength ratio of less than 0.5, the peak strength of the rock was usually stable at the certain extreme value under a constant tensile bond strength. The tensile cracks were negatively correlated with the tensile-shear bond strength ratio, and the shear cracks were positively correlated with the tensile-shear bond strength ratio. The main failure mode of the coarse-grained sandstone in the weakly cemented stratum of the Hongqinghe coal mine is shear failure. The research results can be used to guide the ground control of other mine stopes or roadways with weak cementation lithology.
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Bineshian, Hossein, Abdolhadi Ghazvinian, and Zahra Bineshian. "Comprehensive compressive-tensile strength criterion for intact rock." Journal of Rock Mechanics and Geotechnical Engineering 4, no. 2 (June 2012): 140–48. http://dx.doi.org/10.3724/sp.j.1235.2012.00140.
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Biolzi, L., S. Cattaneo, and G. Rosati. "Flexural/Tensile Strength Ratio in Rock-like Materials." Rock Mechanics and Rock Engineering 34, no. 3 (August 1, 2001): 217–33. http://dx.doi.org/10.1007/s006030170010.
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Yasir, Muhammad, Waqas Ahmed, Ihtisham Islam, Muhammad Sajid, Hammad Tariq Janjuhah, and George Kontakiotis. "Composition, Texture, and Weathering Controls on the Physical and Strength Properties of Selected Intrusive Igneous Rocks from Northern Pakistan." Geosciences 12, no. 7 (July 7, 2022): 273. http://dx.doi.org/10.3390/geosciences12070273.
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This study examines the mineralogy, texture, and weathering grades of intrusive igneous rocks from northern Pakistan, as well as their impacts on physical and strength properties. In comparison to felsic rocks, mafic and intermediate rocks have lower cumulative proportions of quartz, feldspar, and plagioclase, as well as higher specific gravity, strength (i.e., UCS and R-value), and UPV values. Similarly, samples with anhedral grain shapes, irregular boundaries, and fine to medium grain sizes (UD, ANS, and CGN) exhibited greater strength values, with compressive strengths of 121, 118, and 91 MPa and tensile strengths of 11, 9, and 12 MPa, respectively. The physical and strength properties of the investigated samples corresponded well with the weathering grades assigned to them, such as fresh (WG-I), slightly weathered (WG-II), and highly weathered (WG-III). That is, as the grade increased from WG-I to WG-III, the porosity and water absorption increased (0.28% and 0.72%, respectively), whereas the specific gravity, compressive strength, and tensile strength decreased (2.04, 20, and 2.5 MPa, respectively, for CGA). Although the presence of quartz impacts rock strength, no significant association was found between the strength and the maximum and mean grain sizes of other minerals.
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Min, G., D. Fukuda, S. Oh, H. Liu, and S. Cho. "Verification of Spalling Tensile Strength of Rocks using 3D GPGPU-accelerated Hybrid FEM/DEM." IOP Conference Series: Earth and Environmental Science 1124, no. 1 (January 1, 2023): 012117. http://dx.doi.org/10.1088/1755-1315/1124/1/012117.
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Abstract The spalling test is widely applied for evaluating dynamic tensile strength of rock under high strain-rate condition. The dynamic tensile strength is indirectly measured in the spalling test by theoretically assuming the tensile stress level at the failure position of a cylindrical specimen based on the 1D stress wave propagation theory. However, the theoretical estimation method for dynamic tensile strength have not been fully validated since dynamic tensile strength was determined with insufficient understanding of the fracture process, such as crack propagation and stress distribution in the rock specimen during the spalling test, owing to observational limitations in the experiment. Thus, a proper validation method is required for the proposed method, and numerical simulation can be used to validate the proposed method by reproducing the tensile fracture process of the rock specimen during the spalling test. Thus, the dynamic spalling tensile test for rock specimens was reproduced in this study using the GPGPU-based 3D hybrid FDEM that we recently developed. The dynamic tensile fracturing process was analyzed in the simulation of spalling under various strain-rate conditions. Finally, we discussed the application of various theoretical estimation methods to the 3D spalling test.
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Li, Xiaoshuang, Yingchun Li, and Saisai Wu. "Experimental Investigation into the Influences of Weathering on the Mechanical Properties of Sedimentary Rocks." Geofluids 2020 (December 8, 2020): 1–12. http://dx.doi.org/10.1155/2020/8893299.
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The time-dependent behaviors of the sedimentary rocks which refer to the altering of the mechanical and deformable properties of rock elements in the long-term period are of increasing importance in the investigation of the failure mechanism of the rock strata in underground coal mines. In order to obtain the accurate and reliable mechanical parameters of the sedimentary rocks at different weathering grades, the extensive experimental programs including the Brazilian splitting test, uniaxial compression tests, and direct shear tests have been carried out on the specimens that exposed to the nature environments at different durations. The correlation between the weathering grades and mechanical parameters including uniaxial tensile strength, uniaxial compression strength, elastic modulus, Poisson’s ratio, cohesion, and friction coefficient was proposed. The obtained results suggested that uniaxial tensile strength, uniaxial compressive strength, elastic modulus, and cohesion dramatically decreased with increasing weathering time, characterized as the negative exponential relationship in general. The influences of various weathering grades on fracture behavior of the rock specimens were discussed. The cumulative damage of the rock by the weathering time decreased the friction coefficient of the specimens which led to the initiation and propagation of microcrack within the rock at lower stress conditions. The obtained results improved the understanding of the roles of weathering on the mechanical properties of sedimentary rocks, which is helpful in the design of the underground geotechnical structures.
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Xu, Tao, Tian Hui Ma, Chun An Tang, and Zheng Zhao Liang. "Three Dimensional Numerical Approach to Splitting Failure of Rock Discs." Key Engineering Materials 353-358 (September 2007): 921–24. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.921.
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The Brazilian splitting tests have been commonly and widely used as a standardized test method on disc or cylinder specimens to measure the indirect tensile strength of rocks in mining engineering and other rock engineering. In this paper, a novel numerical code, 3D Rock Failure Process Analysis code, was applied to implement the splitting tensile failure tests on rock discs. The influences of the heterogeneity on stress distribution in rock are also discussed and the splitting failure patterns of specimens subjected to Brazilian tests are simulated. The simulated splitting results of rock discs were found quite realistic, which indicate that the rock failure analysis method is applicable and practical for the study of rock disc splitting failure.
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Lu, Aizhong, Ning Zhang, and Guisen Zeng. "An Extension Failure Criterion for Brittle Rock." Advances in Civil Engineering 2020 (October 27, 2020): 1–12. http://dx.doi.org/10.1155/2020/8891248.
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Under the triaxial compressive state, the compressive strain is supposed to happen in the direction of the maximum principal stress, but tensile strain happens in the direction of the minimum principal stress. Moreover, as the intermediate principal stress is not too high, the corresponding strain can also be tensile. If the brittle rock is assumed as linear elastic in the prefailure stage, a new strength criterion based on the sum of the two tensile strains was presented. The new criterion considers the differences in mechanical parameters (i.e., elastic modulus and Poisson’s ratio) under tension and compression. The parameters of the criterion only include Poisson’s ratio and uniaxial strength. And the effect of the intermediate principal stress σ 2 can be reflected. Certain featured failure phenomenon of rock material can be explained well by the proposed criterion. The results of conventional and true triaxial tests can verify the criterion well. Finally, the criterion is compared with the Mohr–Coulomb and Drucker–Prager criteria.
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Li, Li, and Michel Aubertin. "A crack-induced stress approach to describe the tensile strength of transversely isotropic rocks." Canadian Geotechnical Journal 39, no. 1 (February 1, 2002): 1–13. http://dx.doi.org/10.1139/t01-069.
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Rocks are generally more or less anisotropic, depending on their structure at the scale of interest. In engineering applications, the magnitude of such anisotropy must often be determined for compressive as well as tensile loading conditions. In this paper, the authors present the results of an investigation on tensile failure of transversely isotropic rocks, based on Inglis' analytical solution for the stress at the boundary of an elliptical flaw. The strength of transversely isotropic rocks is assumed to be controlled by the maximum tensile local stress along the crack boundary. Equations are developed and compared with tensile test data taken from the literature. The results show that the proposed formulations represent well the direct and indirect tensile strength of anisotropic rocks as a function of bedding plane orientation. It is also shown that the proposed physical model correlates well with the results obtained from more empirical formulations.Key words: rock mechanics, anisotropy, transverse isotropy, tensile strength, Brazilian test, crack.
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Závacký, Martin, Tomáš Majda, Iva Rozsypalová, and Jan Štefaňák. "Moravian greywacke – evaluation of fracture, strength and deformability properties." E3S Web of Conferences 133 (2019): 02003. http://dx.doi.org/10.1051/e3sconf/201913302003.
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This contribution brings overview of mechanical properties of greywacke with focus on fracture mechanics parameters. Investigated rock type is clastic sediment, relatively widespread in Moravia region. The rock type is significantly utilized in construction industry. For purposes of this study, Kobeřice quarry was selected as sampling locality. Mechanical properties were investigated by deformation controlled 3-point bending test. Chevron notch was created on specimens in order to study fracture mechanics parameters. Moreover, deformation controlled uniaxial compression tests were carried out, as well. Specimens were equipped with strain gauges; thus, elastic modulus and the Poisson’s ratio could be determined. Splitting tensile test was employed in order to determine tensile strength. Mean value of fracture toughness KIC was determined to 1.85 MPa·m0.5. Mean value of uniaxial compressive strength was observed at level of 211 MPa and tensile strength reached 19.4 MPa. Hence, the tested greywacke was considered as high strength rock. Brittle type of failure occurred during the tests. The obtained results were compared with values reported for clastic sediments from several localities in the Czech Republic. Moravian greywacke reached significantly high strength in comparison to other clastic sedimentary rocks and can be considered as valuable raw material for purposes of construction industry.
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An, Huaming, Tongshuai Zeng, Zhihua Zhang, and Lei Liu. "Experimental Study of the Rock Mechanism under Coupled High Temperatures and Dynamic Loads." Advances in Civil Engineering 2020 (July 17, 2020): 1–19. http://dx.doi.org/10.1155/2020/8866621.
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With the development of modern society, geomaterials are widely used for infrastructure. These materials often experience dynamic loading and high temperature, which significantly influences the mechanical behaviour of the materials. This research focuses on the effects of the loading rate and high temperature on rock mass in terms of rock mechanism. A state-of-the-art review of rock mechanism under coupled dynamic loads and high temperatures is conducted first. The rock mechanism under static and dynamic loads is introduced. The marble is taken as the rock material for the test, while the split-Hopkinson pressure bar system is used to take the dynamic tests. In addition, the principles of the split-Hopkinson pressure bar are introduced to obtain the dynamic parameters. The fracture patterns of the uniaxial compressive strength test and the Brazilian tensile strength test are obtained and compared with those well documented in the literature. Some curves for the relationships among the loading rate, strain, temperature, compressive or tensile strengths are explained. It is conduced that with the increase of the loading rate, the rock strength increases, while with the increase of the temperature, the rock strength decreases.
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Panthee, Suman, Mahesh Khanal, and T. N. Singh. "Geotechnical and geomechanical characteristics of the rocks along tunnel of Kulekhani III Hydro-electric Project." Journal of Nepal Geological Society 50, no. 1 (December 21, 2016): 39–50. http://dx.doi.org/10.3126/jngs.v50i1.22852.
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Geotechnical and geomechanical properties are important to understand tunnel behaviour and they differ according to rock types. Therefore, tunnel passing through different rock types is selected for the present study. The tunnel alignment of Kulekhani III hydroelectric project crosses five stratigraphic formations which compriseing eight lithological units.
The rocks of the area have most dominantly three sets of joints in which the foliation plane is prominent. In geotechnical study of intact rock, seven geotechnical properties - viz unit weight (γ), uniaxial compressive strength (σci), tensile strength (σti), young’s modulus (Ei), poison’s ratio (ν), friction angle (ci) and cohesion ( i) were measured in lab and on the basis of the intact rock properties five geotechnical properties - uniaxial compressive strength (σcm), tensile strength (σtm), young’s modulus (Em), friction angle (cm) and cohesion ( m) of rock mass were determined.
RMR, Q and GSI were used for geomechanical classification and the distributions of the geomechanical class values were studied. The relationship between UCS of rock mass and geomechanical classifications RMR and Q were studied for all rock types. Quite similar results were observed with both RMR and Q systems. The trend of correlations of each rock type with both classification systems follows almost analogous order. Power type continuous equation is observed for Q and exponential type relation is obtained for RMR. The general trend of correlation of UCS rock mass with RMR and Q is calculated which has R2 more than 0.9. The observed relations were compared with empirical relations proposed by other researchers and the results of the present study lie between the upper and lower boundaries set by other researchers. Among them, harder rocks have better correlation than softer rocks. It is also observed that higher the poisson’s ratio of the rock shown higher the order of linear correlation of rock mass properties with its geomechanical properties.
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Pressacco, Martina, Jari J. J. Kangas, and Timo Saksala. "Numerical Modelling of Microwave Heating Assisted Rock Fracture." Rock Mechanics and Rock Engineering 55, no. 2 (October 31, 2021): 481–503. http://dx.doi.org/10.1007/s00603-021-02685-8.
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AbstractThis paper presents a numerical study on the effects of microwave irradiation on the mechanical properties of hard rock. More specifically, the weakening effect of microwave heating induced damage on the uniaxial compressive and tensile strength of granite-like rock is numerically evaluated. Rock fracture is modelled by means of a damage-viscoplasticity model with separate damage variables for tensile and compressive failure types. We develop a global solution strategy where the electromagnetic problem is solved first separately in COMSOL multiphysics software, and then provided into a staggered implicit solution method for the thermo-mechanical problem. The thermal and mechanical parts of the problem are considered as uncoupled due to the dominance of the microwave-induced heat source. The model performance is tested in 2D finite element simulations of heterogeneous numerical rock specimens subjected first to heating in a microwave oven and then to uniaxial compression and tension tests. According to the results, the compressive and tensile strength of rock can be significantly reduced by microwave heating pretreatment.
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Liu, Bin, Haomin Sang, Zhiqiang Wang, and Yongshui Kang. "Experimental Study on the Mechanical Properties of Rock Fracture after Grouting Reinforcement." Energies 13, no. 18 (September 15, 2020): 4814. http://dx.doi.org/10.3390/en13184814.
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Grouting reinforcement plays an important role in repairing fractures and improving the strength of the surrounding rock. To address practical engineering challenges such as caving and chip off-falling of surrounding rock in deep roadways, normal splitting was adopted to prefabricate fractures on rock samples gathered from underground coal mines. This was done to better match the rock fracture specimen with actual conditions. Based on the elementary unit of a fracture surface, systematic experiments were conducted on the tensile properties of rock fractures after grouting reinforcement, and the shear properties were studied after considering the presence of gas. As per the results, the tensile strength of rock fractures increased with the increase in viscosity of grout, but the overall tensile strength was relatively low. The overall tensile effect of surrounding rock was improved less by grouting approach. When the presence of fracture gas in grouting was considered, the peak shear strength of fractures after grouting was 8.34–29.9% less than that without considering the fracture gas. The cemented pore surface produced by unsaturated cementation in the grouting reinforcement was the main cause of reduction in cohesion and frictional angle of rock fractures. The conclusions of this study have great significance for guiding engineering grouting and evaluating the grouting effect.