The tensile-shear interactive damage(TSID)model is a novel and powerful constitutive model for rock-like materials.This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone.The bas...The tensile-shear interactive damage(TSID)model is a novel and powerful constitutive model for rock-like materials.This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone.The basic parameters of sandstone are determined through a series of static and dynamic tests,including uniaxial compression,Brazilian disc,triaxial compression under varying confining pressures,hydrostatic compression,and dynamic compression and tensile tests with a split Hopkinson pressure bar.Based on the sandstone test results from this study and previous research,a step-by-step procedure for parameter calibration is outlined,which accounts for the categories of the strength surface,equation of state(EOS),strain rate effect,and damage.The calibrated parameters are verified through numerical tests that correspond to the experimental loading conditions.Consistency between numerical results and experimental data indicates the precision and reliability of the calibrated parameters.The methodology presented in this study is scientifically sound,straightforward,and essential for improving the TSID model.Furthermore,it has the potential to contribute to other rock constitutive models,particularly new user-defined models.展开更多
2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock ...2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.展开更多
The phenolic resin-chloroprene rubber was used for sandwieh in manufacturing the vibra-tion damping laminated steel sheet （also ealled laminated sheet）.It is a metal matrix com-posite.The tensile-shear tests have be...The phenolic resin-chloroprene rubber was used for sandwieh in manufacturing the vibra-tion damping laminated steel sheet （also ealled laminated sheet）.It is a metal matrix com-posite.The tensile-shear tests have been conchucted over a range of temperatures from 20Cto 150 C and at the strain rates from 1.67×10<sup>5</sup> to1.67×10<sup>-2</sup>s<sup>-1</sup>.The results show thattest temperature will significantly affect the tensile-shear strength of laminated sheet.and a minimal strength and a minimal aetivation energy occur near 80C.The tensilc-shearbreaking morphology of laminated sheet varies with strain rate and test temperature.展开更多
To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface mi...To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface microstructure and mechanical properties of different FSLW joints were investigated. With increasing the welding speed, the tensile-shear load of FSLW joints produced by three pins presents an increasing firstly and then decreasing trend. Compared with Rpin, the hook and hole defect in the joints made by S-pin and T-pin are eliminated owing to additional eccentric force. Moreover, the joints obtained by T-pin at 75 mm/min have the highest tensile-shear load, and a maximum value of 3.425 kN is produced, which increases by 96.8%.Meanwhile, the pin-tip profile improves significantly the interface reaction depending on the welding temperature. For R-pin, thick brittle intermetallic compounds of about 6.9 μm Al3Mg2and 13.3 μm Al12Mg17layers at the welding interface derived from diffusion reaction are formed, resulting in continuous cracks. However, using T-pin can raise the interface temperature, and which makes the interface liquefy locally to generate only 2.2 μm Al3Mg2layer and dispersive(Al12-Mg17+Mg) eutectic structure. This can release high residual stress and remove welding crack, consequently enhancing the interface properties of T-pin joints.展开更多
Rockburst, an unstable failure of brittle rocks, has been greatly concerned in rock mechanics and rock engineering for more than 100 years. The current understanding on the mechanical mechanism of rockburst is based o...Rockburst, an unstable failure of brittle rocks, has been greatly concerned in rock mechanics and rock engineering for more than 100 years. The current understanding on the mechanical mechanism of rockburst is based on the Coulomb theory, i.e. compressive-shear failure theory. This paper illustrates a series of tensile and tensile-shear fracture phenomena of rockburst, and proposes a methodology for the analysis of fracture mode and its energy dissipation process based on Griffith theory. It is believed that: (1) the fracture modes of rockburst should include compressive-shear, tensile-shear and pure tensile failures; (2) the rupture angle of rock mass decreases with the occurrence of tensile stress; (3) the proportion of kinetic energy in the released strain energy from a rockburst may be much larger than that transferred into surface energy; and (4) the understanding on the tensile and tensile-shear failure modes of rockburst may change the basic thinking of rockburst control, i.e. from keeping the reduction in initial compressive stress σ3 to restricting the creation of secondary tensile stress.展开更多
The traditional limit equilibrium method(LEM) is often used to search for the failure surface with a minimum safety factor of slope. In this method, the failure surface is considered as a shear surface,irrespective of...The traditional limit equilibrium method(LEM) is often used to search for the failure surface with a minimum safety factor of slope. In this method, the failure surface is considered as a shear surface,irrespective of its form. However, tensile cracks are frequently found at the outcrops of landslides. In this study, three sets of tests on small-scale landslides with different inclination angles were conducted. The test results demonstrated that tensile cracks could arise in the slope sliding process and the failure surface is composed of both a shear and a tensile fracture surface. Based on the test results, we used the improved LEM, and replaced the traditional shear failure surface by a tensile-shear coupling one, thus new tensile failure modes for slope stability analysis can be established. The safety factors of slope in different failure modes were compared, which show that when considering soil tensile failure and tensile strength less than a certain value(e.g. 15 kPa, 44 kPa and 55 kPa for linear, circular and logarithmic spiral failure surfaces, respectively), the safety factors of slope with three different failure surfaces are less than the one that did not consider the tensile failure. The most critical failure surfaces of the slope may be composed of shear and tensile damages because the tensile strength of the soil cannot be generally greater than its cohesion.展开更多
The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perfo...The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perform laboratory tests with these complex stress states is significant for establishing new strength criteria. The present paper introduces a new rock testing system with “tensile-compressive-shear”loading functions. The device includes bi-directional and double-range hydraulic cylinders, auxiliary loading equipment, and roller rows that can perform direct compressive-shear tests, direct tensile tests,and direct tensile-shear tests. The testing system provides maximum vertical and lateral loading forces of2000 k N and allows testing cubical rock specimens with dimensions of 0.5 m × 0.5 m × 0.5 m. The performance of the testing machine was evaluated by testing a rock-like material based on cement mortar under compressive-shear, tensile, and tensile-shear stress states. The failure process and deformation characteristics were monitored during loading using acoustic emission(AE) transient recorder,piezoelectric AE sensors, a high-speed camera, and a thermal infrared camera. The failure mechanism was investigated by analyzing AE counts, AE amplitude, strain, and temperature changes on the rock specimen surface. The test results confirmed that the testing system could successfully simulate the abovementioned stress path. The AE counts and amplitude responses were influenced by different failure modes. The temperature response during the compressive-shear test indicated the development of a high-temperature band on the rock specimen surface. In contrast, a negligible temperature change was observed during the tensile and tensile-shear tests. The newly developed multifunctional rock testing system allows laboratory tests under various failure modes. The monitoring results of multiple variables during rock failure tests provide valuable information on failure characteristics.展开更多
The reinforcement effect of geogrids is exerted through the fixing and occlusion with the surrounding soil to ensure the stability of reinforced structure. Based on the friction reinforced mechanism, the geogrids play...The reinforcement effect of geogrids is exerted through the fixing and occlusion with the surrounding soil to ensure the stability of reinforced structure. Based on the friction reinforced mechanism, the geogrids play the role of anti-shear and anti-pulling. So the indexes of interface strength identified by shear and tensile tests?are?usually used to conduct the stability analysis of reinforced structure. At present, the same indexes of interface strength?areadopted in the stability analysis of reinforced structure, where only one of the anti-shearing action or anti-pulling effect of geogrid is considered, which is separated from the practical stress state of geogrids and has certain limitation. To solve the problem, the paper adjusts the interface indexes of geogrids based on the potential sliding surface and the stress state of geogrids when the failure happens. So the method of stability analysis is concluded where cyclic iterative analysis is carried out till the interface characters of geogrids and the unstable mode of the whole structure are the same. The calculation examples of reinforced soil slope in the paper shows that the method can fully reflect the reinforcement of geogrids and can complete the adoption of numerical method in the stability analysis of reinforcement structure.展开更多
The expanded distinct element method(EDEM)was used to investigate the crack growth in rock-like materials under uniaxial compression.The tensile-shear failure criterion and the Griffith failure criterion were implante...The expanded distinct element method(EDEM)was used to investigate the crack growth in rock-like materials under uniaxial compression.The tensile-shear failure criterion and the Griffith failure criterion were implanted into the EDEM to determine the initiation and propagation of pre-existing cracks,respectively.Uniaxial compression experiments were also performed with the artificial rock-like samples to verify the validity of the EDEM.Simulation results indicated that the EDEM model with the tensile-shear failure criterion has strong capabilities for modeling the growth of pre-existing cracks,and model results have strong agreement with the failure and mechanical properties of experimental samples.The EDEM model with the Griffith failure criterion can only simulate the splitting failure of samples due to tensile stresses and is incapable of providing a comprehensive interpretation for the overall failure of rock masses.Research results demonstrated that sample failure primarily resulted from the growth of single cracks(in the form of tensile wing cracks and shear secondary cracks)and the coalescence of two cracks due to the growth of wing cracks in the rock bridge zone.Additionally,the inclination angle of the pre-existing crack clearly influences the final failure pattern of the samples.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.12272247)National Key Project(Grant No.GJXM92579)Major Research and Development Project of Metallurgical Corporation of China Ltd.in the Non-Steel Field(Grant No.2021-5).
文摘The tensile-shear interactive damage(TSID)model is a novel and powerful constitutive model for rock-like materials.This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone.The basic parameters of sandstone are determined through a series of static and dynamic tests,including uniaxial compression,Brazilian disc,triaxial compression under varying confining pressures,hydrostatic compression,and dynamic compression and tensile tests with a split Hopkinson pressure bar.Based on the sandstone test results from this study and previous research,a step-by-step procedure for parameter calibration is outlined,which accounts for the categories of the strength surface,equation of state(EOS),strain rate effect,and damage.The calibrated parameters are verified through numerical tests that correspond to the experimental loading conditions.Consistency between numerical results and experimental data indicates the precision and reliability of the calibrated parameters.The methodology presented in this study is scientifically sound,straightforward,and essential for improving the TSID model.Furthermore,it has the potential to contribute to other rock constitutive models,particularly new user-defined models.
基金supported by the National Natural Science Foundation of China(NSFC)(41941018).
文摘2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.
文摘The phenolic resin-chloroprene rubber was used for sandwieh in manufacturing the vibra-tion damping laminated steel sheet （also ealled laminated sheet）.It is a metal matrix com-posite.The tensile-shear tests have been conchucted over a range of temperatures from 20Cto 150 C and at the strain rates from 1.67×10<sup>5</sup> to1.67×10<sup>-2</sup>s<sup>-1</sup>.The results show thattest temperature will significantly affect the tensile-shear strength of laminated sheet.and a minimal strength and a minimal aetivation energy occur near 80C.The tensilc-shearbreaking morphology of laminated sheet varies with strain rate and test temperature.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52005240 and 52164045)Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province(No.20212BCJ23028)Key Laboratory Fund Project(No.EG202180417).
文摘To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface microstructure and mechanical properties of different FSLW joints were investigated. With increasing the welding speed, the tensile-shear load of FSLW joints produced by three pins presents an increasing firstly and then decreasing trend. Compared with Rpin, the hook and hole defect in the joints made by S-pin and T-pin are eliminated owing to additional eccentric force. Moreover, the joints obtained by T-pin at 75 mm/min have the highest tensile-shear load, and a maximum value of 3.425 kN is produced, which increases by 96.8%.Meanwhile, the pin-tip profile improves significantly the interface reaction depending on the welding temperature. For R-pin, thick brittle intermetallic compounds of about 6.9 μm Al3Mg2and 13.3 μm Al12Mg17layers at the welding interface derived from diffusion reaction are formed, resulting in continuous cracks. However, using T-pin can raise the interface temperature, and which makes the interface liquefy locally to generate only 2.2 μm Al3Mg2layer and dispersive(Al12-Mg17+Mg) eutectic structure. This can release high residual stress and remove welding crack, consequently enhancing the interface properties of T-pin joints.
基金Supported by the National Natural Science Foundation of China (41030749)Ministry of Railways (2009G005-A)Chinese Academy of Sciences (KZCX2-YX-109)
文摘Rockburst, an unstable failure of brittle rocks, has been greatly concerned in rock mechanics and rock engineering for more than 100 years. The current understanding on the mechanical mechanism of rockburst is based on the Coulomb theory, i.e. compressive-shear failure theory. This paper illustrates a series of tensile and tensile-shear fracture phenomena of rockburst, and proposes a methodology for the analysis of fracture mode and its energy dissipation process based on Griffith theory. It is believed that: (1) the fracture modes of rockburst should include compressive-shear, tensile-shear and pure tensile failures; (2) the rupture angle of rock mass decreases with the occurrence of tensile stress; (3) the proportion of kinetic energy in the released strain energy from a rockburst may be much larger than that transferred into surface energy; and (4) the understanding on the tensile and tensile-shear failure modes of rockburst may change the basic thinking of rockburst control, i.e. from keeping the reduction in initial compressive stress σ3 to restricting the creation of secondary tensile stress.
基金financially supported by the National Natural Science Foundation of China (Grant No. 41572277)the Guangdong Natural Science Foundation (Grant No. 2015A030313118)
文摘The traditional limit equilibrium method(LEM) is often used to search for the failure surface with a minimum safety factor of slope. In this method, the failure surface is considered as a shear surface,irrespective of its form. However, tensile cracks are frequently found at the outcrops of landslides. In this study, three sets of tests on small-scale landslides with different inclination angles were conducted. The test results demonstrated that tensile cracks could arise in the slope sliding process and the failure surface is composed of both a shear and a tensile fracture surface. Based on the test results, we used the improved LEM, and replaced the traditional shear failure surface by a tensile-shear coupling one, thus new tensile failure modes for slope stability analysis can be established. The safety factors of slope in different failure modes were compared, which show that when considering soil tensile failure and tensile strength less than a certain value(e.g. 15 kPa, 44 kPa and 55 kPa for linear, circular and logarithmic spiral failure surfaces, respectively), the safety factors of slope with three different failure surfaces are less than the one that did not consider the tensile failure. The most critical failure surfaces of the slope may be composed of shear and tensile damages because the tensile strength of the soil cannot be generally greater than its cohesion.
基金funding support from the National Natural Science Foundation of China (Grant Nos. U1806226 and 51979154)。
文摘The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perform laboratory tests with these complex stress states is significant for establishing new strength criteria. The present paper introduces a new rock testing system with “tensile-compressive-shear”loading functions. The device includes bi-directional and double-range hydraulic cylinders, auxiliary loading equipment, and roller rows that can perform direct compressive-shear tests, direct tensile tests,and direct tensile-shear tests. The testing system provides maximum vertical and lateral loading forces of2000 k N and allows testing cubical rock specimens with dimensions of 0.5 m × 0.5 m × 0.5 m. The performance of the testing machine was evaluated by testing a rock-like material based on cement mortar under compressive-shear, tensile, and tensile-shear stress states. The failure process and deformation characteristics were monitored during loading using acoustic emission(AE) transient recorder,piezoelectric AE sensors, a high-speed camera, and a thermal infrared camera. The failure mechanism was investigated by analyzing AE counts, AE amplitude, strain, and temperature changes on the rock specimen surface. The test results confirmed that the testing system could successfully simulate the abovementioned stress path. The AE counts and amplitude responses were influenced by different failure modes. The temperature response during the compressive-shear test indicated the development of a high-temperature band on the rock specimen surface. In contrast, a negligible temperature change was observed during the tensile and tensile-shear tests. The newly developed multifunctional rock testing system allows laboratory tests under various failure modes. The monitoring results of multiple variables during rock failure tests provide valuable information on failure characteristics.
文摘The reinforcement effect of geogrids is exerted through the fixing and occlusion with the surrounding soil to ensure the stability of reinforced structure. Based on the friction reinforced mechanism, the geogrids play the role of anti-shear and anti-pulling. So the indexes of interface strength identified by shear and tensile tests?are?usually used to conduct the stability analysis of reinforced structure. At present, the same indexes of interface strength?areadopted in the stability analysis of reinforced structure, where only one of the anti-shearing action or anti-pulling effect of geogrid is considered, which is separated from the practical stress state of geogrids and has certain limitation. To solve the problem, the paper adjusts the interface indexes of geogrids based on the potential sliding surface and the stress state of geogrids when the failure happens. So the method of stability analysis is concluded where cyclic iterative analysis is carried out till the interface characters of geogrids and the unstable mode of the whole structure are the same. The calculation examples of reinforced soil slope in the paper shows that the method can fully reflect the reinforcement of geogrids and can complete the adoption of numerical method in the stability analysis of reinforcement structure.
文摘The expanded distinct element method(EDEM)was used to investigate the crack growth in rock-like materials under uniaxial compression.The tensile-shear failure criterion and the Griffith failure criterion were implanted into the EDEM to determine the initiation and propagation of pre-existing cracks,respectively.Uniaxial compression experiments were also performed with the artificial rock-like samples to verify the validity of the EDEM.Simulation results indicated that the EDEM model with the tensile-shear failure criterion has strong capabilities for modeling the growth of pre-existing cracks,and model results have strong agreement with the failure and mechanical properties of experimental samples.The EDEM model with the Griffith failure criterion can only simulate the splitting failure of samples due to tensile stresses and is incapable of providing a comprehensive interpretation for the overall failure of rock masses.Research results demonstrated that sample failure primarily resulted from the growth of single cracks(in the form of tensile wing cracks and shear secondary cracks)and the coalescence of two cracks due to the growth of wing cracks in the rock bridge zone.Additionally,the inclination angle of the pre-existing crack clearly influences the final failure pattern of the samples.
