Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more...Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsl^j bar systems, which include both split Hopkinson pressure bar (SHPB) and split Hopkinson tension bar (SHTB) systems. Significant progress has been made on the quantification of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system. This review aims to fully describe and critically assess the detailed procedures and principles of tech- niques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined, followed by the key loading techniques that are useful for dynamic rock tests with SHPB (i.e. pulse shaping, momentum-trap and multi-axial loading techniques). Various measurement techniques for rock tests in SHPB (i.e. X-ray micro computed tomography (CT), laser gap gauge (LGG), digital image corre- lation (DIC), Moir~ method, caustics method, photoelastic coating method, dynamic infrared thermog- raphy) are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements (i.e. dynamic compression, tension, bending and shear tests), dynamic fracture measurements (i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity), and dy- namic techniques for studying the influences of temperature and pore water.展开更多
As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study ...As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study the dynamic properties of soft and hard composite rocks with different thickness ratios, this paper utilizes cement, quartz sand and gypsum powder to construct soft and hard composite rock specimens and utilizes a combination of indoor tests, numerical calculations, and theoretical analyses to investigate the mechanical properties of soft and hard composite rock bodies. The test results reveal that:(1) When the proportion of hard rock increases from 20% to 50%, the strength of the combined rock body increases by 69.14 MPa and 87 MPa when the hard rock face and soft rock face are loaded, respectively;however, when the proportion of hard rock is the same, the compressive strength of the hard rock face impact is 9%-17% greater than that of the soft rock face impact;(2) When a specimen of soft and hard combined rock body is subjected to impact loading, the damage mode involves mixed tension and shear damage, and the cracks generally first appear at the ends of the specimen, then develop on the laminar surface from the impact surface, and finally end in the overall damage of the soft rock part. The development rate and the total number of cracks in the same specimen when the hard rock face is impacted are significantly greater than those when the soft rock face is impacted;(3) By introducing Weibull’s statistical strength theory to establish the damage variables of soft-hard combined rock bodies, combined with the DP strength criterion, the damage model and the Kelvin body are concatenated to obtain a statistical damage constitutive model, which can better fit the full stress-strain curve of soft-hard combined rock body specimens under a single impact load.展开更多
Rocks are increasingly used in extreme environments characterised by high loading rates and high confining pressures.Thus the fracture properties of rocks under dynamic loading and confinements are critical in various...Rocks are increasingly used in extreme environments characterised by high loading rates and high confining pressures.Thus the fracture properties of rocks under dynamic loading and confinements are critical in various rock mechanics and rock engineering problems.Due to the transient nature of dynamic loading,the dynamic fracture tests of rocks are much more challenging than their static counterparts.Understanding the dynamic fracture behaviour of geomaterials relies significantly on suitable and reliable dynamic fracture testing methods.One of such methods is the notched semi-circle bend(NSCB)test combined with the advanced split Hopkinson pressure bar(SHPB)system,which has been recommended by the International Society for Rock Mechanics and Rock Engineering(ISRM)as the standard method for the determination of dynamic fracture toughness.The dynamic NSCB-SHPB method can provide detailed insights into dynamic fracture properties including initiation fracture toughness,fracture energy,propagation fracture toughness and fracture velocity.This review aims to fully describe the detailed principles and state-of-the-art applications of dynamic NSCB-SHPB techniques.The history and principles of dynamic NSCB-SHPB tests for rocks are outlined,and then the applications of dynamic NSCB-SHPB method(including the measurements of initiation and propagation fracture toughnesses and the limiting fracture velocity,the size effect and the digital image correlation(DIC)experiments)are discussed.Further,other applications of dynamic NSCB-SHPB techniques(i.e.the thermal,moisture and anisotropy effects on the dynamic fracture properties of geomaterials,and dynamic fracture toughness of geomaterials under pre-loading and hydrostatic pressures)are presented.展开更多
In this study,a waveform modification method was proposed using a self-designed heating device combined with the split Hopkinson pressure bar(SHPB)technique for determination of dynamic behaviors of rock at high tempe...In this study,a waveform modification method was proposed using a self-designed heating device combined with the split Hopkinson pressure bar(SHPB)technique for determination of dynamic behaviors of rock at high temperature.Firstly,the temperature gradient distribution on the incident bar was measured according to the variation of elastic modulus of the bar with temperature,and the relationship between the longitudinal wave velocity and temperature of the bar was obtained based on onedimensional stress wave theory.The incident bar with a temperature gradient was divided into a series of microelements,and then the transmission coefficient of the whole incident bar was obtained.Finally,the stress wave was modified by the transmission coefficient from 25℃ to 600℃.This method was used to study the dynamic properties of rock at high temperature,which not only preserves a classical SHPB device,but also effectively ensures the accuracy of the experimental results.A dynamic Brazilian disc experiment was carried out to explore the influences of loading rate and temperature on dynamic tensile strength of sandstone at high temperature using the proposed waveform modification method.展开更多
Layered rock mass of significant strength changes for adjacent layers is frequently observed in underground excavation,and dynamic loading is a prevalent scenario generated during excavation.In order to improve the dr...Layered rock mass of significant strength changes for adjacent layers is frequently observed in underground excavation,and dynamic loading is a prevalent scenario generated during excavation.In order to improve the driving efficiency and reduce engineering accidents,dynamic compression characteristics of this kind of rock mass should be understood.The dynamic properties of a layered composite rock mass are investigated through a series of rock tests and numerical simulations.The rock mass is artificially made of various proportions of sand,cement and water to control the distinct strength variations at various composite layers separated by parallel bedding planes.All rock specimens are prefabricated in a specially designed mould and then cut into 50 mm in diameter and 50 mm in height for split Hopkinson pressure bar(SHPB)dynamic compression testing.The test results reveal that increasing strain rate causes the increases of peak strength,σ_p,and the corresponding failure strain,ε_p,while the dynamic elastic modulus,E_d,remains almost unchanged.Interestingly,under the same strain rates,Ed of the composite rock specimen is found to decline first and then increase as the dip angle of bedding plane increases.The obtained rock failure patterns due to various dip angles lead to failure modes that could be classified into four categories from our dynamic tests.Also,a series of counterpart numerical simulations has been undertaken,showing that dynamic responses are in good agreement with those obtained from the SHPB tests.The numerical analysis enables us to Iook into the dynamic characteristics of the composite rock mass subjected to a broader range of strain rates and dip angles than these being tested.展开更多
This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were ...This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data(e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structuraletemporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize(minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.展开更多
Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems.Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more ...Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems.Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsky bar systems, which include both split Hopkinson pressure bar(SHPB) and split Hopkinson tension bar(SHTB) systems. Signi fi cant progress has been made on the quanti fi cation of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system.This review aims to fully describe and critically assess the detailed procedures and principles of techniques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined,followed by the key loading techniques that are useful for dynamic rock tests with SHPB(i.e. pulse shaping, momentum-trap and multi-axial loading techniques). Various measurement techniques for rock tests in SHPB(i.e. X-ray micro computed tomography(CT), laser gap gauge(LGG), digital image correlation(DIC), Moiré method, caustics method, photoelastic coating method, dynamic infrared thermography) are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements(i.e.dynamic compression, tension, bending and shear tests), dynamic fracture measurements(i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity), and dynamic techniques for studying the in fl uences of temperature and pore water.展开更多
To study the physical and mechanical properties of coal rock after treatment at different temperatures under impact loading, dynamic compression experiments were conducted by using a split Hopkinson pressure bar(SHPB)...To study the physical and mechanical properties of coal rock after treatment at different temperatures under impact loading, dynamic compression experiments were conducted by using a split Hopkinson pressure bar(SHPB). The stress–strain curves of specimens under impact loading were obtained, and then four indexes affected by temperature were analyzed in the experiment: the longitudinal wave velocity, elastic modulus, peak stress and peak strain. Among these indexes, the elastic modulus was utilized to express the specimens' damage characteristics. The results show that the stress–strain curves under impact loading lack the stage of micro-fissure closure and the slope of the elastic deformation stage is higher than that under static loading. Due to the dynamic loading effect, the peak stress increases while peak strain decreases. The dynamic mechanical properties of coal rock show obvious temperature effects. The longitudinal wave velocity, elastic modulus and peak stress all decrease to different extents with increasing temperature, while the peak strain increases continuously. During the whole heating process, the thermal damage value continues to increase linearly, which indicates that the internal structure of coal rock is gradually damaged by high temperature.展开更多
文摘Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems. Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsl^j bar systems, which include both split Hopkinson pressure bar (SHPB) and split Hopkinson tension bar (SHTB) systems. Significant progress has been made on the quantification of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system. This review aims to fully describe and critically assess the detailed procedures and principles of tech- niques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined, followed by the key loading techniques that are useful for dynamic rock tests with SHPB (i.e. pulse shaping, momentum-trap and multi-axial loading techniques). Various measurement techniques for rock tests in SHPB (i.e. X-ray micro computed tomography (CT), laser gap gauge (LGG), digital image corre- lation (DIC), Moir~ method, caustics method, photoelastic coating method, dynamic infrared thermog- raphy) are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements (i.e. dynamic compression, tension, bending and shear tests), dynamic fracture measurements (i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity), and dy- namic techniques for studying the influences of temperature and pore water.
基金supported by the Xi’an Key Laboratory of Geotechnical and Underground Engineering Open Fund Project (XKLGUEKF20-03)the Natural Science Basic Research Program of Shaanxi Province General Project-Youth Project(2024JC-YBQN-0258)。
文摘As one of the most common occurring geological landforms in deep rock formations, the dynamic mechanical properties of layered composite rock bodies under impact loading have been widely studied by scholars. To study the dynamic properties of soft and hard composite rocks with different thickness ratios, this paper utilizes cement, quartz sand and gypsum powder to construct soft and hard composite rock specimens and utilizes a combination of indoor tests, numerical calculations, and theoretical analyses to investigate the mechanical properties of soft and hard composite rock bodies. The test results reveal that:(1) When the proportion of hard rock increases from 20% to 50%, the strength of the combined rock body increases by 69.14 MPa and 87 MPa when the hard rock face and soft rock face are loaded, respectively;however, when the proportion of hard rock is the same, the compressive strength of the hard rock face impact is 9%-17% greater than that of the soft rock face impact;(2) When a specimen of soft and hard combined rock body is subjected to impact loading, the damage mode involves mixed tension and shear damage, and the cracks generally first appear at the ends of the specimen, then develop on the laminar surface from the impact surface, and finally end in the overall damage of the soft rock part. The development rate and the total number of cracks in the same specimen when the hard rock face is impacted are significantly greater than those when the soft rock face is impacted;(3) By introducing Weibull’s statistical strength theory to establish the damage variables of soft-hard combined rock bodies, combined with the DP strength criterion, the damage model and the Kelvin body are concatenated to obtain a statistical damage constitutive model, which can better fit the full stress-strain curve of soft-hard combined rock body specimens under a single impact load.
基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)through the Discovery Grant No.72031326supported by Mitacs through the Mitacs Accelerate Programme
文摘Rocks are increasingly used in extreme environments characterised by high loading rates and high confining pressures.Thus the fracture properties of rocks under dynamic loading and confinements are critical in various rock mechanics and rock engineering problems.Due to the transient nature of dynamic loading,the dynamic fracture tests of rocks are much more challenging than their static counterparts.Understanding the dynamic fracture behaviour of geomaterials relies significantly on suitable and reliable dynamic fracture testing methods.One of such methods is the notched semi-circle bend(NSCB)test combined with the advanced split Hopkinson pressure bar(SHPB)system,which has been recommended by the International Society for Rock Mechanics and Rock Engineering(ISRM)as the standard method for the determination of dynamic fracture toughness.The dynamic NSCB-SHPB method can provide detailed insights into dynamic fracture properties including initiation fracture toughness,fracture energy,propagation fracture toughness and fracture velocity.This review aims to fully describe the detailed principles and state-of-the-art applications of dynamic NSCB-SHPB techniques.The history and principles of dynamic NSCB-SHPB tests for rocks are outlined,and then the applications of dynamic NSCB-SHPB method(including the measurements of initiation and propagation fracture toughnesses and the limiting fracture velocity,the size effect and the digital image correlation(DIC)experiments)are discussed.Further,other applications of dynamic NSCB-SHPB techniques(i.e.the thermal,moisture and anisotropy effects on the dynamic fracture properties of geomaterials,and dynamic fracture toughness of geomaterials under pre-loading and hydrostatic pressures)are presented.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41972283 and 51774325)。
文摘In this study,a waveform modification method was proposed using a self-designed heating device combined with the split Hopkinson pressure bar(SHPB)technique for determination of dynamic behaviors of rock at high temperature.Firstly,the temperature gradient distribution on the incident bar was measured according to the variation of elastic modulus of the bar with temperature,and the relationship between the longitudinal wave velocity and temperature of the bar was obtained based on onedimensional stress wave theory.The incident bar with a temperature gradient was divided into a series of microelements,and then the transmission coefficient of the whole incident bar was obtained.Finally,the stress wave was modified by the transmission coefficient from 25℃ to 600℃.This method was used to study the dynamic properties of rock at high temperature,which not only preserves a classical SHPB device,but also effectively ensures the accuracy of the experimental results.A dynamic Brazilian disc experiment was carried out to explore the influences of loading rate and temperature on dynamic tensile strength of sandstone at high temperature using the proposed waveform modification method.
基金supported by the National Natural Science Foundation of China(Grant No.51608174)the Programmes for Science and Technology Development of Henan Province,China(Grant No.192102310014)。
文摘Layered rock mass of significant strength changes for adjacent layers is frequently observed in underground excavation,and dynamic loading is a prevalent scenario generated during excavation.In order to improve the driving efficiency and reduce engineering accidents,dynamic compression characteristics of this kind of rock mass should be understood.The dynamic properties of a layered composite rock mass are investigated through a series of rock tests and numerical simulations.The rock mass is artificially made of various proportions of sand,cement and water to control the distinct strength variations at various composite layers separated by parallel bedding planes.All rock specimens are prefabricated in a specially designed mould and then cut into 50 mm in diameter and 50 mm in height for split Hopkinson pressure bar(SHPB)dynamic compression testing.The test results reveal that increasing strain rate causes the increases of peak strength,σ_p,and the corresponding failure strain,ε_p,while the dynamic elastic modulus,E_d,remains almost unchanged.Interestingly,under the same strain rates,Ed of the composite rock specimen is found to decline first and then increase as the dip angle of bedding plane increases.The obtained rock failure patterns due to various dip angles lead to failure modes that could be classified into four categories from our dynamic tests.Also,a series of counterpart numerical simulations has been undertaken,showing that dynamic responses are in good agreement with those obtained from the SHPB tests.The numerical analysis enables us to Iook into the dynamic characteristics of the composite rock mass subjected to a broader range of strain rates and dip angles than these being tested.
基金supported by IHC Merwede B.V. as well as by Russian Foundation for Basic Research (Grant Nos. 13-0100349 and 14-01-31510)Russian Science Foundation (“support and development”, Grant No. 14-19-01637)Saint Petersburg University (Grant No. 6.38.243.2014)
文摘This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data(e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structuraletemporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize(minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.
基金support by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Discovery Grant No. 72031326
文摘Dynamic properties of rocks are important in a variety of rock mechanics and rock engineering problems.Due to the transient nature of the loading, dynamic tests of rock materials are very different from and much more challenging than their static counterparts. Dynamic tests are usually conducted using the split Hopkinson bar or Kolsky bar systems, which include both split Hopkinson pressure bar(SHPB) and split Hopkinson tension bar(SHTB) systems. Signi fi cant progress has been made on the quanti fi cation of various rock dynamic properties, owing to the advances in the experimental techniques of SHPB system.This review aims to fully describe and critically assess the detailed procedures and principles of techniques for dynamic rock tests using split Hopkinson bars. The history and principles of SHPB are outlined,followed by the key loading techniques that are useful for dynamic rock tests with SHPB(i.e. pulse shaping, momentum-trap and multi-axial loading techniques). Various measurement techniques for rock tests in SHPB(i.e. X-ray micro computed tomography(CT), laser gap gauge(LGG), digital image correlation(DIC), Moiré method, caustics method, photoelastic coating method, dynamic infrared thermography) are then discussed. As the main objective of the review, various dynamic measurement techniques for rocks using SHPB are described, including dynamic rock strength measurements(i.e.dynamic compression, tension, bending and shear tests), dynamic fracture measurements(i.e. dynamic imitation and propagation fracture toughness, dynamic fracture energy and fracture velocity), and dynamic techniques for studying the in fl uences of temperature and pore water.
基金Projects(41272304,51304241,51204068)supported by the National Natural Science Foundation of ChinaProject(2014M552164)supported by the Postdoctoral Science Foundation of ChinaProject(20130162120015)supported by the PhD Programs Foundation of Ministry of Education of China
文摘To study the physical and mechanical properties of coal rock after treatment at different temperatures under impact loading, dynamic compression experiments were conducted by using a split Hopkinson pressure bar(SHPB). The stress–strain curves of specimens under impact loading were obtained, and then four indexes affected by temperature were analyzed in the experiment: the longitudinal wave velocity, elastic modulus, peak stress and peak strain. Among these indexes, the elastic modulus was utilized to express the specimens' damage characteristics. The results show that the stress–strain curves under impact loading lack the stage of micro-fissure closure and the slope of the elastic deformation stage is higher than that under static loading. Due to the dynamic loading effect, the peak stress increases while peak strain decreases. The dynamic mechanical properties of coal rock show obvious temperature effects. The longitudinal wave velocity, elastic modulus and peak stress all decrease to different extents with increasing temperature, while the peak strain increases continuously. During the whole heating process, the thermal damage value continues to increase linearly, which indicates that the internal structure of coal rock is gradually damaged by high temperature.