2025 Vol. 45, No. 6
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2025, 45(6): 061001.
doi: 10.11883/bzycj-2024-0424
Abstract:
Propagation features of blast-induced stress waves undergo substantial alterations as they traverse heterogeneous interfaces. In rock engineering, the prevalence of discontinuous structural planes, such as joints and fissures, becomes increasingly pronounced with increasing burial depth. To gain a comprehensive insight into the dynamic response and damage mechanism, an explicit dynamics numerical method incorporating the ALE algorithm and fluid-solid coupling technology was adopted, which allows for precise simulation of the fracture process within jointed rock mass under the combined effects of confining pressure and blasting load. Based on the time-domain recurrence theory, the transmission and reflection coefficients of the stress wave were calculated, and the propagation process and features of the stress wave were then analyzed by the explosion photoelasticity test using an epoxy resin plate. Additionally, the Riedel-Hiermaier-Thoma (RHT) damage model was used to investigate the influence of different joint angles and confining pressures on cracking behavior. Furthermore, the cracks were quantitatively assessed using the FracPaQ program. Finally, the damage mechanism of the jointed rock mass was revealed by analyzing the principal stress distribution and displacement change as well as the dynamic stress intensity factors (DSIFs) of the joint tip. The results show that both the joint and the anisotropic pressure have a guiding effect on crack extension, and the effect of the anisotropic pressure will be weakened by the presence of the joint. For the anisotropic pressure condition, the stress wave transmission and reflection coefficients tended to decrease and increase, respectively, with increasing pressure in the horizontal direction. From the change rule of normal and tangential displacement on both sides of the joint surface, it is found that shear stress is the main cause of tip-wing crack expansion. An analysis of the DSIFs reveals that tensile cracks predominantly contribute to damage at the joint tip during the initial phase of blasting, with shear cracks becoming the dominant form of damage in the later stages.
Propagation features of blast-induced stress waves undergo substantial alterations as they traverse heterogeneous interfaces. In rock engineering, the prevalence of discontinuous structural planes, such as joints and fissures, becomes increasingly pronounced with increasing burial depth. To gain a comprehensive insight into the dynamic response and damage mechanism, an explicit dynamics numerical method incorporating the ALE algorithm and fluid-solid coupling technology was adopted, which allows for precise simulation of the fracture process within jointed rock mass under the combined effects of confining pressure and blasting load. Based on the time-domain recurrence theory, the transmission and reflection coefficients of the stress wave were calculated, and the propagation process and features of the stress wave were then analyzed by the explosion photoelasticity test using an epoxy resin plate. Additionally, the Riedel-Hiermaier-Thoma (RHT) damage model was used to investigate the influence of different joint angles and confining pressures on cracking behavior. Furthermore, the cracks were quantitatively assessed using the FracPaQ program. Finally, the damage mechanism of the jointed rock mass was revealed by analyzing the principal stress distribution and displacement change as well as the dynamic stress intensity factors (DSIFs) of the joint tip. The results show that both the joint and the anisotropic pressure have a guiding effect on crack extension, and the effect of the anisotropic pressure will be weakened by the presence of the joint. For the anisotropic pressure condition, the stress wave transmission and reflection coefficients tended to decrease and increase, respectively, with increasing pressure in the horizontal direction. From the change rule of normal and tangential displacement on both sides of the joint surface, it is found that shear stress is the main cause of tip-wing crack expansion. An analysis of the DSIFs reveals that tensile cracks predominantly contribute to damage at the joint tip during the initial phase of blasting, with shear cracks becoming the dominant form of damage in the later stages.
2025, 45(6): 061101.
doi: 10.11883/bzycj-2024-0399
Abstract:
As the global demand for resources continues to rise, the scale of deep underground engineering development expands, facing increasingly complex geological conditions and high-stress environments. This shift has made the study of the dynamic characteristics of deep rock masses with structural planes a hot and challenging research topic in recent years. Firstly, a systematic summary of the dynamic shear and tensile characteristics of structural planes was conducted, along with an in-depth analysis of the impact of various factors on their dynamic behavior. Additionally, the effect of structural plane effects on the dynamic properties of rock masses was explored, particularly regarding dynamic strength and deformation. Furthermore, the triggering mechanisms and prevention technologies for common deep dynamic disasters, such as rock bursts, large deformations, and dynamic pressure, have been reviewed, emphasizing the importance of establishing an effective theoretical and technical system. Finally, a forward-looking perspective on future research directions for the dynamic characteristics of deep rock masses with structural planes and disaster prevention technologies is offered, calling for the integration of emerging technologies and theoretical methods to enhance the depth and breadth of research, thereby promoting the safety and effectiveness in engineering practice.
As the global demand for resources continues to rise, the scale of deep underground engineering development expands, facing increasingly complex geological conditions and high-stress environments. This shift has made the study of the dynamic characteristics of deep rock masses with structural planes a hot and challenging research topic in recent years. Firstly, a systematic summary of the dynamic shear and tensile characteristics of structural planes was conducted, along with an in-depth analysis of the impact of various factors on their dynamic behavior. Additionally, the effect of structural plane effects on the dynamic properties of rock masses was explored, particularly regarding dynamic strength and deformation. Furthermore, the triggering mechanisms and prevention technologies for common deep dynamic disasters, such as rock bursts, large deformations, and dynamic pressure, have been reviewed, emphasizing the importance of establishing an effective theoretical and technical system. Finally, a forward-looking perspective on future research directions for the dynamic characteristics of deep rock masses with structural planes and disaster prevention technologies is offered, calling for the integration of emerging technologies and theoretical methods to enhance the depth and breadth of research, thereby promoting the safety and effectiveness in engineering practice.
2025, 45(6): 061411.
doi: 10.11883/bzycj-2024-0335
Abstract:
In order to take into account the influence of the crack roughness, first of all, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. The result shows that the rockmass dynamic climax strength increases from 26.42 MPa to 27.28 and 28.37 MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.24 MPa to 27.28 and 28.80 MPa with φb increasing from 0° to 15° and 30° respectively. The rockmass dynamic climax strength decreases from 31.37 MPa to 27.28 and 23.90 MPa with 2a increasing from 1cm to 2 and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
In order to take into account the influence of the crack roughness, first of all, on basis of the calculation model for the rockmass macroscopic damage variable which can take into account the crack geometry parameter, strength parameter and deformation parameter, a calculation model for the rockmass macroscopic damage variable is proposed by introducing the JRC-JCS shear strength model for the rough crack established by Barton, which can consider the crack roughness. Secondly, the proposed calculation model is introduced into the uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack, which both considers the coupling of the macroscopic and microscopic defects, and then a uniaxial compressive dynamic damage model for the rock mass with the non-persistent crack is established which can consider the crack roughness at the same time. Finally, the effect of crack roughness JRC and crack basic friction angle φb and crack length 2a on rockmass dynamic mechanical property is studied with the parametric sensitivity analysis. The result shows that the rockmass dynamic climax strength increases from 26.42 MPa to 27.28 and 28.37 MPa with JRC increasing from 0 to 10 and 20 respectively. The rockmass dynamic climax strength increases from 26.24 MPa to 27.28 and 28.80 MPa with φb increasing from 0° to 15° and 30° respectively. The rockmass dynamic climax strength decreases from 31.37 MPa to 27.28 and 23.90 MPa with 2a increasing from 1cm to 2 and 3cm respectively. At the same time, in order to describe the influence of the crack roughness more accurately, the crack fractal dimension is introduced into the dynamic damage model for the rock mass, which not only improves the calculation accuracy of the model, but also broadens its application range, which is more convenient for practical engineering application.
2025, 45(6): 061412.
doi: 10.11883/bzycj-2024-0336
Abstract:
Based on continuum damage mechanics, a rock dynamic constitutive model with coupled elastic-plastic damage was established. This model took the unified strength theory as the yield criterion and introduces the dynamic tensile-compressive ratio to fully reflect the strain rate effect. The effective plastic strain and volumetric plastic strain were used to represent the compressive damage variable, and the effective plastic strain was used to represent the tensile damage variable, thereby reflecting the different damage evolution laws of rocks under tensile and compressive conditions. A piecewise function was adopted to describe the different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model was numerically implemented based on Fortran language and the LS-DYNA user material customization interface (Umat). The established constitutive model is verified by three classical calculation examples, namely, the uniaxial and triaxial compression tests of rocks, the uniaxial tensile test of rocks, and the ballistic test of rocks. The results showed that this constitutive model can comprehensively describe the static and dynamic mechanical behaviors of rocks.
Based on continuum damage mechanics, a rock dynamic constitutive model with coupled elastic-plastic damage was established. This model took the unified strength theory as the yield criterion and introduces the dynamic tensile-compressive ratio to fully reflect the strain rate effect. The effective plastic strain and volumetric plastic strain were used to represent the compressive damage variable, and the effective plastic strain was used to represent the tensile damage variable, thereby reflecting the different damage evolution laws of rocks under tensile and compressive conditions. A piecewise function was adopted to describe the different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model was numerically implemented based on Fortran language and the LS-DYNA user material customization interface (Umat). The established constitutive model is verified by three classical calculation examples, namely, the uniaxial and triaxial compression tests of rocks, the uniaxial tensile test of rocks, and the ballistic test of rocks. The results showed that this constitutive model can comprehensively describe the static and dynamic mechanical behaviors of rocks.
2025, 45(6): 061413.
doi: 10.11883/bzycj-2024-0405
Abstract:
To investigate the effect of high temperature on the energy characteristics of marble, ANSYS/LS-DYNA was used to carry out dynamic compression simulation tests on marble with six temperature gradients at five impact velocities to analyze the mechanical properties of marble under high-temperature dynamic loading and the temperature effect on energy evolution, and to explore the energy criterion for strength failure of high-temperature marble from the perspective of energy dissipation. The results show that the Holmquist-Johnson-Cook (HJC) constitutive model can reasonably and effectively simulate the dynamic damage process of marble under different temperatures. With the increase in temperature, the dynamic peak strength and dynamic elastic modulus of marble exhibit a quadratic negative correlation with temperature, the dynamic peak strain exhibits a quadratic positive correlation with temperature, and the damage morphology is changed from X-type to conjugate shear damage. The increase in temperature reduces the energy storage capacity of the marble specimen to a certain extent, while the effect of high temperature on the energy dissipation capacity of marble is transformed from a facilitating effect to an inhibiting effect with 600 ℃ as the cut-off point. When the temperature reaches 600 ℃, the peak strength is significantly reduced, the ductility of the marble increases, crushing damage is presented, and the dissipated strain energy reaches the maximum value. 600 ℃ can be used as the threshold temperature for the brittle-delayed transformation of the marble. Based on the characteristics of the energy evolution process, the point of a steep increase in dissipated strain energy is regarded as a precursor information point of the precursor of overall instability and damage of marble. The inflection point at which the growth rate of the elastic energy consumption ratio first appears is defined according to the curve of the stress-elastic energy consumption ratio-strain relationship as the energy criterion of the strength failure of marble.
To investigate the effect of high temperature on the energy characteristics of marble, ANSYS/LS-DYNA was used to carry out dynamic compression simulation tests on marble with six temperature gradients at five impact velocities to analyze the mechanical properties of marble under high-temperature dynamic loading and the temperature effect on energy evolution, and to explore the energy criterion for strength failure of high-temperature marble from the perspective of energy dissipation. The results show that the Holmquist-Johnson-Cook (HJC) constitutive model can reasonably and effectively simulate the dynamic damage process of marble under different temperatures. With the increase in temperature, the dynamic peak strength and dynamic elastic modulus of marble exhibit a quadratic negative correlation with temperature, the dynamic peak strain exhibits a quadratic positive correlation with temperature, and the damage morphology is changed from X-type to conjugate shear damage. The increase in temperature reduces the energy storage capacity of the marble specimen to a certain extent, while the effect of high temperature on the energy dissipation capacity of marble is transformed from a facilitating effect to an inhibiting effect with 600 ℃ as the cut-off point. When the temperature reaches 600 ℃, the peak strength is significantly reduced, the ductility of the marble increases, crushing damage is presented, and the dissipated strain energy reaches the maximum value. 600 ℃ can be used as the threshold temperature for the brittle-delayed transformation of the marble. Based on the characteristics of the energy evolution process, the point of a steep increase in dissipated strain energy is regarded as a precursor information point of the precursor of overall instability and damage of marble. The inflection point at which the growth rate of the elastic energy consumption ratio first appears is defined according to the curve of the stress-elastic energy consumption ratio-strain relationship as the energy criterion of the strength failure of marble.
2025, 45(6): 061421.
doi: 10.11883/bzycj-2024-0346
Abstract:
To investigate the fracture and permeability characteristics of sandstone-type uranium ore under cyclic impact, a Hopkinson bar experimental system was used to load sandstone samples by cyclic impacts. The dynamic mechanical properties of the sandstone samples were measured after 3, 6 and 9 impacts. Subsequently, the impacted sandstone samples were subjected to CT scanning, and the crack images obtained from the scans were reconstructed in three-dimensions to measure the changes in pore and fracture parameters. The internal structures and damages in the impacted samples were then analyzed. Furthermore, a microscopic seepage simulation was performed to analyze the permeability of the samples, revealing the changes in the simulated permeability. Finally, permeability tests were conducted on the impacted samples to measure the variations in the actual permeability. Results show that cyclic impacts cause cumulative damage in the specimens, reducing their dynamic mechanical properties. As the number of impacts increases, energy in the specimens accumulates and releases cyclically. This cyclic accumulation and release of energy lead to a process of crack "expansion, compaction, re-expansion, re-compaction". During the cyclic impact process, small and isolated cracks inside the specimen gradually develop into larger, interconnected fractures. Simultaneously, medium-sized cracks exhibit dual effects of faulting and connectivity, presenting nonlinear characteristics. Cyclic impacts induce more complex fractures in the specimens, leading to an increased number of fluid seepage pathways and a larger scale of seepage. When subjected to three cycles of impact, the sample forms a single crack, resulting in a permeability increase of 340.91%−380.00%. After six cycles of impact, the cracks begin to connect, leading to a permeability increase of1468.18 %−2893.33 %. With nine cycles of impact, a connected network of cracks forms, resulting in a permeability increase of 4718.18 %−9380.00 %. The cyclic impact significantly enhances the permeability of sandstone, with crack propagation and connectivity being the key driving factors for the increase in permeability.
To investigate the fracture and permeability characteristics of sandstone-type uranium ore under cyclic impact, a Hopkinson bar experimental system was used to load sandstone samples by cyclic impacts. The dynamic mechanical properties of the sandstone samples were measured after 3, 6 and 9 impacts. Subsequently, the impacted sandstone samples were subjected to CT scanning, and the crack images obtained from the scans were reconstructed in three-dimensions to measure the changes in pore and fracture parameters. The internal structures and damages in the impacted samples were then analyzed. Furthermore, a microscopic seepage simulation was performed to analyze the permeability of the samples, revealing the changes in the simulated permeability. Finally, permeability tests were conducted on the impacted samples to measure the variations in the actual permeability. Results show that cyclic impacts cause cumulative damage in the specimens, reducing their dynamic mechanical properties. As the number of impacts increases, energy in the specimens accumulates and releases cyclically. This cyclic accumulation and release of energy lead to a process of crack "expansion, compaction, re-expansion, re-compaction". During the cyclic impact process, small and isolated cracks inside the specimen gradually develop into larger, interconnected fractures. Simultaneously, medium-sized cracks exhibit dual effects of faulting and connectivity, presenting nonlinear characteristics. Cyclic impacts induce more complex fractures in the specimens, leading to an increased number of fluid seepage pathways and a larger scale of seepage. When subjected to three cycles of impact, the sample forms a single crack, resulting in a permeability increase of 340.91%−380.00%. After six cycles of impact, the cracks begin to connect, leading to a permeability increase of
2025, 45(6): 061422.
doi: 10.11883/bzycj-2024-0417
Abstract:
To investigate the dynamic shear mechanical response and post-damage permeability characteristics of rough structural planes, a dynamic shear system was utilized to conduct shear tests on rough structural planes of sandstone under varying shear rate conditions. The effects of shear rate and roughness coefficient on peak shear strength and slip behaviors were analyzed. After the shear test, the influence of dynamic shear on the damage characteristics of rough structural surfaces was analyzed using three-dimensional scanning technology. Subsequently, seepage tests were conducted on damaged structural surfaces under different confining pressures to further investigate the subsequent seepage characteristics of damaged structural surfaces after dynamic shearing. The results of dynamic shear tests show that the dynamic peak shear strength of sandstone structural planes exhibits a decreasing trend with the shear rate, and shear rate influence on shear stiffness is insignificant. As the shear rate increases from 50 mm/s to 210 mm/s, the peak shear strength of structural planes with joint roughness coefficient of 12.43 declines from 8.49 MPa to 6.88 MPa. In addition, the dynamic peak shear strength of structural planes increases with the roughness under the same shear rate condition. The frequency of height distribution of damaged structural planes decreases with the shear rate. Under the same roughness condition, the damage degree of the structural plane generally increases with the shear rate, resulting in a decline in crack opening and thus affecting the permeability properties of the structural plane. The flow test results indicate that the relationship between the hydraulic gradient and the volumetric flow rate of the damaged structural plane adheres to Forchheimer’s law. In addition, the transmissivity of the damaged structural plane decreases with the shear rate under the same confining pressure condition, while increasing with the joint roughness coefficient.
To investigate the dynamic shear mechanical response and post-damage permeability characteristics of rough structural planes, a dynamic shear system was utilized to conduct shear tests on rough structural planes of sandstone under varying shear rate conditions. The effects of shear rate and roughness coefficient on peak shear strength and slip behaviors were analyzed. After the shear test, the influence of dynamic shear on the damage characteristics of rough structural surfaces was analyzed using three-dimensional scanning technology. Subsequently, seepage tests were conducted on damaged structural surfaces under different confining pressures to further investigate the subsequent seepage characteristics of damaged structural surfaces after dynamic shearing. The results of dynamic shear tests show that the dynamic peak shear strength of sandstone structural planes exhibits a decreasing trend with the shear rate, and shear rate influence on shear stiffness is insignificant. As the shear rate increases from 50 mm/s to 210 mm/s, the peak shear strength of structural planes with joint roughness coefficient of 12.43 declines from 8.49 MPa to 6.88 MPa. In addition, the dynamic peak shear strength of structural planes increases with the roughness under the same shear rate condition. The frequency of height distribution of damaged structural planes decreases with the shear rate. Under the same roughness condition, the damage degree of the structural plane generally increases with the shear rate, resulting in a decline in crack opening and thus affecting the permeability properties of the structural plane. The flow test results indicate that the relationship between the hydraulic gradient and the volumetric flow rate of the damaged structural plane adheres to Forchheimer’s law. In addition, the transmissivity of the damaged structural plane decreases with the shear rate under the same confining pressure condition, while increasing with the joint roughness coefficient.
2025, 45(6): 061423.
doi: 10.11883/bzycj-2024-0353
Abstract:
In practical engineering, rock frequently suffers from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock under cyclic dynamic disturbances, cyclic impact tests of single-jointed gabbro (SJG) were conducted using a split Hopkinson pressure bar (SHPB) test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the increase rate decreases with larger joint inclination angles. Under low-stress impact loading, the compressive-shear stress within single-jointed specimens is insufficient to generate shear cracks. The failure of specimens primarily results from the progressive propagation of tensile cracks induced by tensile stress, which eventually coalesce with the joint. The failure mechanism of multi-jointed rock masses resembles that of single-jointed rock masses. During cyclic impact loading, both compaction of micro-defects and initiation of micro-cracks at joints occur simultaneously. However, the impact resistance of multi-jointed specimens depends on whether the cracks can interconnect the joints. For intact rock specimens, the failure process initially involves compaction of micro-defects, followed by probabilistic activation of micro-cracks, ultimately leading to specimen failure.
In practical engineering, rock frequently suffers from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock under cyclic dynamic disturbances, cyclic impact tests of single-jointed gabbro (SJG) were conducted using a split Hopkinson pressure bar (SHPB) test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the increase rate decreases with larger joint inclination angles. Under low-stress impact loading, the compressive-shear stress within single-jointed specimens is insufficient to generate shear cracks. The failure of specimens primarily results from the progressive propagation of tensile cracks induced by tensile stress, which eventually coalesce with the joint. The failure mechanism of multi-jointed rock masses resembles that of single-jointed rock masses. During cyclic impact loading, both compaction of micro-defects and initiation of micro-cracks at joints occur simultaneously. However, the impact resistance of multi-jointed specimens depends on whether the cracks can interconnect the joints. For intact rock specimens, the failure process initially involves compaction of micro-defects, followed by probabilistic activation of micro-cracks, ultimately leading to specimen failure.
2025, 45(6): 061431.
doi: 10.11883/bzycj-2024-0409
Abstract:
The influence of reflected explosion stress waves on dynamic crack propagation behavior , as well as the connection between dynamic cracks and pre-existing cracks, was studied using dynamic photoelastic experiments. A high-speed camera was used to capture the full field photoelastic isochromatic fringe pattern of horizontally expanding explosive cracks. The explosive crack is a directional crack generated by detonating explosives in a blast hole containing a horizontal V-shaped groove. The propagation process of explosive cracks can be divided into three different stages. In the first stage, explosive detonation produces dynamic cracks. Simultaneously incident explosion stress waves propagate and interact with prefabricated vertical cracks. In the second stage, the reflected explosion stress waves interact with dynamic cracks. In the third stage, dynamic cracks connect with pre-existing cracks and release unloading stress waves. Considering both singular and non-singular stresses in the near-crack-tip region, three far-field-controlled constant stresses were adopted. The mixed mode stress intensity factor of dynamic cracks under the action of reflected stress waves was analyzed and calculated using the Newton-Raphson iteration method. The results indicate that the leading edge of the reflected pressure wave acts as a stretching wave and the trailing edge behaves as a compression wave. The tensile component of the reflected pressure wave applies tensile stress to the crack tip, increasing the dynamic stress intensity factor KⅠ and promoting crack propagation. On the contrary, the compressive component of the reflected pressure wave applies compressive stress to the crack tip, resulting in a decrease in the dynamic stress intensity factor KⅠ and suppressing crack propagation. Reflected shear waves can cause unstable crack propagation. It causes changes in the direction and velocity of crack propagation, resulting in a wavy crack trajectory. After the penetration of dynamic cracks and prefabricated cracks, the elastic energy stored near the crack tip is rapidly released to generate unloading waves. Due to the action of the unloading wave, stress is concentrated at the tip of the pre-existing crack, causing the formation of a secondary crack at the tip of the pre-existing crack.
The influence of reflected explosion stress waves on dynamic crack propagation behavior , as well as the connection between dynamic cracks and pre-existing cracks, was studied using dynamic photoelastic experiments. A high-speed camera was used to capture the full field photoelastic isochromatic fringe pattern of horizontally expanding explosive cracks. The explosive crack is a directional crack generated by detonating explosives in a blast hole containing a horizontal V-shaped groove. The propagation process of explosive cracks can be divided into three different stages. In the first stage, explosive detonation produces dynamic cracks. Simultaneously incident explosion stress waves propagate and interact with prefabricated vertical cracks. In the second stage, the reflected explosion stress waves interact with dynamic cracks. In the third stage, dynamic cracks connect with pre-existing cracks and release unloading stress waves. Considering both singular and non-singular stresses in the near-crack-tip region, three far-field-controlled constant stresses were adopted. The mixed mode stress intensity factor of dynamic cracks under the action of reflected stress waves was analyzed and calculated using the Newton-Raphson iteration method. The results indicate that the leading edge of the reflected pressure wave acts as a stretching wave and the trailing edge behaves as a compression wave. The tensile component of the reflected pressure wave applies tensile stress to the crack tip, increasing the dynamic stress intensity factor KⅠ and promoting crack propagation. On the contrary, the compressive component of the reflected pressure wave applies compressive stress to the crack tip, resulting in a decrease in the dynamic stress intensity factor KⅠ and suppressing crack propagation. Reflected shear waves can cause unstable crack propagation. It causes changes in the direction and velocity of crack propagation, resulting in a wavy crack trajectory. After the penetration of dynamic cracks and prefabricated cracks, the elastic energy stored near the crack tip is rapidly released to generate unloading waves. Due to the action of the unloading wave, stress is concentrated at the tip of the pre-existing crack, causing the formation of a secondary crack at the tip of the pre-existing crack.
2025, 45(6): 061432.
doi: 10.11883/bzycj-2024-0414
Abstract:
To understand the interaction between joints and blasting stresses and optimizing blasting parameters in jointed rock, the impact of different joint inclinations on blasting fragmentation was studied through a combination of tests and numerical simulations. In this study, a group of concrete model specimens containing joints with different angles was used in the blasting tests to investigate the effect of joint inclination on blast fragmentation. During tests, detonators were placed in vertical boreholes in the specimens and detonated, while high-speed camera was used to capture the fragmentation process. The dynamic responses of joint surfaces at different time intervals after detonation was observed, and blasting fragmentation distribution was extracted using image processing techniques. The effect of joint inclination on blasting fragmentation was analyzed. The propagation of stress waves and the evolution of strain fields within the specimens was obtained in finite element numerical simulations by using LS-DYNA. Experimental and numerical results indicated that the joints have a significant influence on the distribution of blasting fragmentation and the propagation of stress waves. The impact of the joints on the blasting performance was mainly attributed to the reflection of blasting waves from the joints, which was related to the deformation characteristics of the joints. With the increase of joint inclination, the blasting fragmentation initially decreased followed by an increase. The effective stress and peak particle velocity transmission in the joints decreased overall with the increase of joint inclination, but showed a rebound between 45° and 60°. This suggests approximately 45° is the most favorable condition for rock fragmentation under blasting. Moreover, the results obtained from numerical crack network reconstruction and image processing revealed that there was an upsurge in the occurrence of vertical cracks in the specimen as the joint inclination increased, while a decline was observed in the presence of horizontal cracks.
To understand the interaction between joints and blasting stresses and optimizing blasting parameters in jointed rock, the impact of different joint inclinations on blasting fragmentation was studied through a combination of tests and numerical simulations. In this study, a group of concrete model specimens containing joints with different angles was used in the blasting tests to investigate the effect of joint inclination on blast fragmentation. During tests, detonators were placed in vertical boreholes in the specimens and detonated, while high-speed camera was used to capture the fragmentation process. The dynamic responses of joint surfaces at different time intervals after detonation was observed, and blasting fragmentation distribution was extracted using image processing techniques. The effect of joint inclination on blasting fragmentation was analyzed. The propagation of stress waves and the evolution of strain fields within the specimens was obtained in finite element numerical simulations by using LS-DYNA. Experimental and numerical results indicated that the joints have a significant influence on the distribution of blasting fragmentation and the propagation of stress waves. The impact of the joints on the blasting performance was mainly attributed to the reflection of blasting waves from the joints, which was related to the deformation characteristics of the joints. With the increase of joint inclination, the blasting fragmentation initially decreased followed by an increase. The effective stress and peak particle velocity transmission in the joints decreased overall with the increase of joint inclination, but showed a rebound between 45° and 60°. This suggests approximately 45° is the most favorable condition for rock fragmentation under blasting. Moreover, the results obtained from numerical crack network reconstruction and image processing revealed that there was an upsurge in the occurrence of vertical cracks in the specimen as the joint inclination increased, while a decline was observed in the presence of horizontal cracks.
2025, 45(6): 061441.
doi: 10.11883/bzycj-2024-0403
Abstract:
The shear mechanical properties and deformation damage mechanism of the double structural planes of traditional anchor cables and new anchor cables with C-shaped tube structures (abbreviated as ACC) under different loading rate conditions were investigated through experimental and numerical simulation analyses. Dual structural face shear tests were conducted at shear displacement loading rates of 2, 10, 20, 30, and 40 mm/min under 55 MPa concrete specimen strength and 200 kN preload, with shear deformation curves, peak structural shear loads, steel wire damage patterns, and structural plane shear strength contributions as the main parameters considered. The results show that the loading rate significantly affects the shear performance of the structure. Within a certain loading rate interval, influenced by the damage accumulation rate and the strain rate strengthening effect, the structure exhibits characteristics of strength weakening and strengthening, respectively, with a large variation interval in shear load-carrying capacity. Near the structural plane, the support structure shows a combination of tensile and shear damage. However, the ACC structure, due to the presence of the C-shaped tube, exhibits lower stress concentration effects, reduced fluctuation in the test curve, and significantly weakened internal steel wire damage compared to traditional anchor cables. Meanwhile, the numerical model of the double shear test of the ACC structure, constructed based on the test results, exhibits high accuracy. Numerical simulations of dynamic loading tests demonstrate that the anchoring system formed by the ACC structure has a good energy absorption effect, which becomes more pronounced with increasing impact energy. Under high-speed impact, the ACC structure is significantly affected by the strain rate reinforcement effect, with higher shear load capacity at greater impact velocities.
The shear mechanical properties and deformation damage mechanism of the double structural planes of traditional anchor cables and new anchor cables with C-shaped tube structures (abbreviated as ACC) under different loading rate conditions were investigated through experimental and numerical simulation analyses. Dual structural face shear tests were conducted at shear displacement loading rates of 2, 10, 20, 30, and 40 mm/min under 55 MPa concrete specimen strength and 200 kN preload, with shear deformation curves, peak structural shear loads, steel wire damage patterns, and structural plane shear strength contributions as the main parameters considered. The results show that the loading rate significantly affects the shear performance of the structure. Within a certain loading rate interval, influenced by the damage accumulation rate and the strain rate strengthening effect, the structure exhibits characteristics of strength weakening and strengthening, respectively, with a large variation interval in shear load-carrying capacity. Near the structural plane, the support structure shows a combination of tensile and shear damage. However, the ACC structure, due to the presence of the C-shaped tube, exhibits lower stress concentration effects, reduced fluctuation in the test curve, and significantly weakened internal steel wire damage compared to traditional anchor cables. Meanwhile, the numerical model of the double shear test of the ACC structure, constructed based on the test results, exhibits high accuracy. Numerical simulations of dynamic loading tests demonstrate that the anchoring system formed by the ACC structure has a good energy absorption effect, which becomes more pronounced with increasing impact energy. Under high-speed impact, the ACC structure is significantly affected by the strain rate reinforcement effect, with higher shear load capacity at greater impact velocities.
2025, 45(6): 061442.
doi: 10.11883/bzycj-2024-0466
Abstract:
The gradient stresses in the surrounding rock caused by deep excavation and the naturally occurring slow-dipping hard structural planes of the rock are critical factors influencing the characteristics of rockburst.Through triaxial loading-unidirectional unloading tests conducted on large-scale (400 mm×600 mm×1 000 mm) artificial rock specimens containing prefabricated hard slow-dipping structural planes using a gas-liquid composite loading rockburst simulation system, this study systematically investigated rockburst evolution mechanisms and mechanisms of damage. A multi-modal monitoring approach incorporating digital image correlation (DIC), acoustic emission (AE) detection, infrared thermography, and high-speed photography was employed to capture critical parameters including energy released patterns, surface infrared radiation characteristics, DIC strain field evolution, and crack propagation dynamics during rockburst development. The results of the study show that the presence of the slow-dipping structural plane has a controlling effect on the damage pattern of the specimen,greatly constrains the boundaries and morphology of rockburst craters, and accelerates the occurrence of rockburst. It is verified that the location of rockbursts in the specimens is mainly in the area between the structural planes of the specimens. The infrared radiation values and DIC strain fields in this area are much higher than those in the rest of the unloading surface before the damage. As the angle of the slow-dipping structural plane increases, the peak and cumulative acoustic emission energy of the specimen increases, the proportion of shear damage to total damage produced increaces, intensity of rockburst spawned increaces.
The gradient stresses in the surrounding rock caused by deep excavation and the naturally occurring slow-dipping hard structural planes of the rock are critical factors influencing the characteristics of rockburst.Through triaxial loading-unidirectional unloading tests conducted on large-scale (400 mm×600 mm×1 000 mm) artificial rock specimens containing prefabricated hard slow-dipping structural planes using a gas-liquid composite loading rockburst simulation system, this study systematically investigated rockburst evolution mechanisms and mechanisms of damage. A multi-modal monitoring approach incorporating digital image correlation (DIC), acoustic emission (AE) detection, infrared thermography, and high-speed photography was employed to capture critical parameters including energy released patterns, surface infrared radiation characteristics, DIC strain field evolution, and crack propagation dynamics during rockburst development. The results of the study show that the presence of the slow-dipping structural plane has a controlling effect on the damage pattern of the specimen,greatly constrains the boundaries and morphology of rockburst craters, and accelerates the occurrence of rockburst. It is verified that the location of rockbursts in the specimens is mainly in the area between the structural planes of the specimens. The infrared radiation values and DIC strain fields in this area are much higher than those in the rest of the unloading surface before the damage. As the angle of the slow-dipping structural plane increases, the peak and cumulative acoustic emission energy of the specimen increases, the proportion of shear damage to total damage produced increaces, intensity of rockburst spawned increaces.
2025, 45(6): 061443.
doi: 10.11883/bzycj-2024-0395
Abstract:
The viscous characteristics of granular fault gouge significantly impact the dynamic mechanical behavior of faults, yet the problem of determining the viscosity of these interlayers at different slip velocities remains unresolved. This article presents theoretical research on this issue. The Maxwell relaxation model was employed to study the evolution of force chains in granular fault gouge during slow shearing of granular gouge, and the dependence of force chain length on shear strain rate, effective extension speed of shear bands, and strength of the granular medium was derived. The relaxation time of the shear band in granular fault gouge, the expression for the viscosity coefficient of the granular medium, and the conditions for the transformation of solid-liquid mechanical behavior of the granular medium were established. The validity of this model was verified through comparison with existing experimental data. For high-speed fault slip shear, the motion of the granular medium exhibits turbulent characteristics. Statistical physics was used to describe the interaction between granular particles in granular fault gouge, and it was found that the viscosity coefficient is inversely proportional to the shear rate at high slip rates. The research results have fundamental significance for understanding the viscous and other physico-mechanical properties of granular gouge in faults.
The viscous characteristics of granular fault gouge significantly impact the dynamic mechanical behavior of faults, yet the problem of determining the viscosity of these interlayers at different slip velocities remains unresolved. This article presents theoretical research on this issue. The Maxwell relaxation model was employed to study the evolution of force chains in granular fault gouge during slow shearing of granular gouge, and the dependence of force chain length on shear strain rate, effective extension speed of shear bands, and strength of the granular medium was derived. The relaxation time of the shear band in granular fault gouge, the expression for the viscosity coefficient of the granular medium, and the conditions for the transformation of solid-liquid mechanical behavior of the granular medium were established. The validity of this model was verified through comparison with existing experimental data. For high-speed fault slip shear, the motion of the granular medium exhibits turbulent characteristics. Statistical physics was used to describe the interaction between granular particles in granular fault gouge, and it was found that the viscosity coefficient is inversely proportional to the shear rate at high slip rates. The research results have fundamental significance for understanding the viscous and other physico-mechanical properties of granular gouge in faults.
