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Y. Wang
Beijing Key Laboratory of Urban Underground Space Engineering, Department of Civil Engineering, School of Civil & Resource Engineering, University of Science & Technology Beijing, Beijing 100083, China

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Journal article
Published: 23 January 2021 in Engineering Fracture Mechanics
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Rock mass is often subjected to complicated stress disturbance in many civil and mining engineering. This work aims to investigate the fatigue mechanical characteristics of marble having different interbed orientation subjected to multi-level constant-amplitude (MLCA) cyclic loads. The impacts of interbed structure on rock fracture and energy characteristics were investigated and characterized experimentally. The experimental results reveal that the deformation, strength, lifetime, damping characteristics, and energy release and dissipation are all impacted by the interbed structure. From the change of hysteresis loop shape, damping ratio, and dissipated energy, a two-phase damage evolution characteristic at each cyclic loading stage is observed. The hysteresis loop area, damping ratio and dissipated energy all decrease with increasing cyclic number within a cyclic loading stage. At the start of each cyclic stage, the sudden growth of axial stress contributes a lot to the rock damage compared to the followed cyclic loads. In addition, based on the energy dissipation principle, a fatigue damage model was proposed to describe rock accumulative damage. It is shown that the model can well describe the damage accumulation regardless the rock structure. Moreover, good agreement is found between the CT images and energy analysis, and it is suggested that it is the rock structure that controls the energy dissipation and release pattern.

ACS Style

Y. Wang; Y.F. Yi; C.H. Li; J.Q. Han. Anisotropic fracture and energy characteristics of a Tibet marble exposed to multi-level constant-amplitude (MLCA) cyclic loads: A lab-scale testing. Engineering Fracture Mechanics 2021, 244, 107550 .

AMA Style

Y. Wang, Y.F. Yi, C.H. Li, J.Q. Han. Anisotropic fracture and energy characteristics of a Tibet marble exposed to multi-level constant-amplitude (MLCA) cyclic loads: A lab-scale testing. Engineering Fracture Mechanics. 2021; 244 ():107550.

Chicago/Turabian Style

Y. Wang; Y.F. Yi; C.H. Li; J.Q. Han. 2021. "Anisotropic fracture and energy characteristics of a Tibet marble exposed to multi-level constant-amplitude (MLCA) cyclic loads: A lab-scale testing." Engineering Fracture Mechanics 244, no. : 107550.

Journal article
Published: 16 January 2021 in International Journal of Rock Mechanics and Mining Sciences
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Freeze-thaw-fatigue (FTF) testing was carried out on Tibet marble at lab-scale by considering various Freeze-Thaw (FT) cycles and multi-level cyclic loading. The aim is to investigate the evolution of deformation and damage related parameters as well as the hysteresis behavior. The test results show that an increase of FT cycles and fatigue load level both accelerate the damage rate of marble. A rock suffering more FT cycles shows a much larger axial strain rate, radial strain rate and increasing Poisson's ratio. The relation of axial strain rate, radial strain rate and Poisson's ratio rate versus fatigue load level can be fitted by an exponential function. A warning level is defined according to the evolution of radial strain and Poisson's ratio which can inform before dilation starts. Moreover, the hysteresis behavior of stress-strain is investigated. It has been proven, that the proposed two indexes, “advance ratio” and “lag ratio” are effective precursors for rock failure prediction if subjected to FTF actions. The drastic drop of the “advance ratio” and the increase of the “lag ratio” are the indicators for forthcoming failure. The recommended warning limits for “advance ratio” and “lag ratio” for the tested marble are 5% and 70%, respectively.

ACS Style

Zhengyang Song; Yu Wang; Heinz Konietzky; Xin Cai. Mechanical behavior of marble exposed to freeze-thaw-fatigue loading. International Journal of Rock Mechanics and Mining Sciences 2021, 138, 104648 .

AMA Style

Zhengyang Song, Yu Wang, Heinz Konietzky, Xin Cai. Mechanical behavior of marble exposed to freeze-thaw-fatigue loading. International Journal of Rock Mechanics and Mining Sciences. 2021; 138 ():104648.

Chicago/Turabian Style

Zhengyang Song; Yu Wang; Heinz Konietzky; Xin Cai. 2021. "Mechanical behavior of marble exposed to freeze-thaw-fatigue loading." International Journal of Rock Mechanics and Mining Sciences 138, no. : 104648.

Original paper
Published: 13 November 2020 in Rock Mechanics and Rock Engineering
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This work aims at investigating the fracture evolution and energy characteristics of marble subjected to fatigue cyclic loading and confining pressure unloading (FC-CPU) conditions. Although rocks under separated fatigue cyclic loading and triaxial unloading conditions have been well studied, little is known about the dependence of the fatigue damage accumulation on the subsequent confining pressure unloading condition that influences the rock fracture behaviors. In this work, the servo-controlled GCTS 2000 rock mechanical system combined with the post-test X-ray computed tomography (CT) scanning technique were used to reveal the fracture behaviors of the marble samples. The samples were tested at three stages: the static loading stage, the fatigue cyclic loading stage, and the confining pressure unloading stage. Results show that the damage index-cycle number curve shows a different pattern—the damage increasing rate is different for the samples experiencing different fatigue damage. The damage accumulation at the fatigue cyclic stage influences the final failure mode and energy conversion. In addition, post-test CT scanning further reveals the effects of fatigue cycles on the crack pattern, as well as the stimulated crack scale and density after FC-CPU testing depending on the fatigue cycle. Furthermore, the stored elastic energy decreases and the dissipated energy increases with increasing fatigue cycle at the fatigue loading stage, and the energy conversion is consistent with the crack pattern analysis. By investigating the failure mechanism of marble under FC-CPU conditions, a theoretical basis for rock dynamic disaster prediction can be created.

ACS Style

Y. Wang; W. K. Feng; R. L. Hu; C. H. Li. Fracture Evolution and Energy Characteristics During Marble Failure Under Triaxial Fatigue Cyclic and Confining Pressure Unloading (FC-CPU) Conditions. Rock Mechanics and Rock Engineering 2020, 54, 799 -818.

AMA Style

Y. Wang, W. K. Feng, R. L. Hu, C. H. Li. Fracture Evolution and Energy Characteristics During Marble Failure Under Triaxial Fatigue Cyclic and Confining Pressure Unloading (FC-CPU) Conditions. Rock Mechanics and Rock Engineering. 2020; 54 (2):799-818.

Chicago/Turabian Style

Y. Wang; W. K. Feng; R. L. Hu; C. H. Li. 2020. "Fracture Evolution and Energy Characteristics During Marble Failure Under Triaxial Fatigue Cyclic and Confining Pressure Unloading (FC-CPU) Conditions." Rock Mechanics and Rock Engineering 54, no. 2: 799-818.

Journal article
Published: 12 November 2020 in Engineering Fracture Mechanics
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Rocks in civil and mining engineering usually experience rather complex stress disturbance. Rock dynamic mechanical behaviors under constant stress amplitude condition have been widely studied. However, the rock fracture evolution characteristics subjected to multi-level cyclic loading conditions are not well understood. In this work, multi-level cyclic compressive loading experiments were performed on marble with interbed orientation of 0°, 30°, 60° and 90°. Anisotropic fracture evolution characteristics were revealed using dynamic stress strain descriptions and post-test CT scanning technique. Results show that rock fatigue deformation, strength, lifetime, dynamic elastic modulus and damping ratio are all impacted by rock structure. The interbed structure plays a dominant role in fracture evolution compared with natural fracture and pyrite band. Rock stiffness degrades and damping ratio increases with the increase of interbed orientation. In addition, a two-phase damage accumulation pattern was found for marble under multi-level cyclic loading condition. A damage evolution model was first established to model damage accumulation, the proposed model fits well to the experimental data. Moreover, post-test CT scanning reveals the internal crack coalescence pattern and failure mode is impacted by the interactions of interbeds, natural fracture and pyrite bands. The rock bridge structure in marble with 60° and 90° interbed orientation alters the crack propagation path. Although the crack pattern is relatively simple at rock bridge segment, much more energy is needed to drive crack propagation. The testing results are expected to improve the understanding of the influence of rock structure on fracture evolution when subjected to variable stress amplitude loading conditions.

ACS Style

Y. Wang; Y.Z. Hu; S.H. Gao. Dynamic mechanical behaviors of interbedded marble subjected to multi-level uniaxial compressive cyclic loading conditions: An insight into fracture evolution analysis. Engineering Fracture Mechanics 2020, 241, 107410 .

AMA Style

Y. Wang, Y.Z. Hu, S.H. Gao. Dynamic mechanical behaviors of interbedded marble subjected to multi-level uniaxial compressive cyclic loading conditions: An insight into fracture evolution analysis. Engineering Fracture Mechanics. 2020; 241 ():107410.

Chicago/Turabian Style

Y. Wang; Y.Z. Hu; S.H. Gao. 2020. "Dynamic mechanical behaviors of interbedded marble subjected to multi-level uniaxial compressive cyclic loading conditions: An insight into fracture evolution analysis." Engineering Fracture Mechanics 241, no. : 107410.

Journal article
Published: 13 October 2020 in Engineering Fracture Mechanics
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Rock mass containing discontinues is often subjected to fatigue loads in many mining and civil engineering. The stress amplitude (SA) as an important factor impacts rock fracture evolution during fatigue loading condition. Existing effects to investigate the impacts of SA on rock fatigue behaviors were mainly on constant SA loading condition, the influences of incremental stress amplitude (ISA) for rock subjected to cyclic uniaxial increasing-amplitude conditions is not well understood. In this work, uniaxial increasing-amplitude fatigue loads and post-test 3D CT scanning experiments were conducted on granite containing two pre-existing flaws. Our experimental results reveal the impact of four applied ISA (i.e., 5, 10, 20 and 30 MPa) on rock fracture evolution, energy conversion and crack network pattern at rock bridge segment. The damage accumulation and volumetric deformation increase with the increase of applied ISA. The accelerated damage evolution stage is different for sample with different ISA, and it starts to appear the earliest for a sample subjected to ISA of 30 MPa. Energy conversion analysis reveals that the dissipated energy used to drive the crack propagation is relatively large for a sample with higher ISA. Post-test 3D CT visualization reveals a most striking finding that the crack network pattern becomes complicated as the applied ISA increases. It is suggested that crack coalescence between the flaws is easy to be formed for rock subjected to low ISA, rock bridge segment fracturing is stress amplitude dependent. The testing results are expected to improve the understanding of the influence of stress amplitude on the fatigue behaviors of pre-flawed rock when rock mass is subjected to increasing-amplitude stress disturbance.

ACS Style

Y. Wang; C.H. Li; J.Q. Han. On the effect of stress amplitude on fracture and energy evolution of pre-flawed granite under uniaxial increasing-amplitude fatigue loads. Engineering Fracture Mechanics 2020, 240, 107366 .

AMA Style

Y. Wang, C.H. Li, J.Q. Han. On the effect of stress amplitude on fracture and energy evolution of pre-flawed granite under uniaxial increasing-amplitude fatigue loads. Engineering Fracture Mechanics. 2020; 240 ():107366.

Chicago/Turabian Style

Y. Wang; C.H. Li; J.Q. Han. 2020. "On the effect of stress amplitude on fracture and energy evolution of pre-flawed granite under uniaxial increasing-amplitude fatigue loads." Engineering Fracture Mechanics 240, no. : 107366.

Original paper
Published: 23 September 2020 in Arabian Journal of Geosciences
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Cemented waste rock backfill (CWRB), which is a mixture of tailings, waste rock, cement, and water, is subjected to the combination actions in underground mining operations. While the strength requirement of CWRB has been widely studied, the mesoscopic damage evolution mechanisms of waste block proportion (WBP) on its geomechanical characteristics are still not well understood. In the present paper, the crack damage evolution of CWRB samples were characterized using real-time X-ray CT under uniaxial compression. The effects of waste block on the stress strain responses, stress dilatancy behaviors, meso-structure changes, and the cracking behaviors were investigated. The results show that strength of CWBR is influenced by waste block proportion, and strength increases are due to geomechanical effects related to propagation of tortuous failure surfaces. Besides, for sample with high WBP, interlocking among the waste blocks also improves the overall stiffness and strength of CWRB compared with tailing paste sample. Volumetric dilatancy caused by the damage and cracking behavior has a close link with the meso-structural changes, which are controlled by the interactions between the waste rock and cemented tailing paste. The crack damage behavior is quite inhomogeneous and strongly influenced by the waste block size, shape, and distribution. Our study demonstrates that it is feasible to reveal the physical mesoscopic mechanism of crack damage evolution for CWRB by using X-ray CT, and the meso-damage cracking behaviors should be deeply studied to ensure stability of pillar during mining activities.

ACS Style

Yu Wang; Yonggang Xiao; Zhiqiang Hou; Changhong Li; XiaoMing Wei. In situ X-ray computed tomography (CT) investigation of crack damage evolution for cemented paste backfill with marble waste block admixture under uniaxial deformation. Arabian Journal of Geosciences 2020, 13, 1 -16.

AMA Style

Yu Wang, Yonggang Xiao, Zhiqiang Hou, Changhong Li, XiaoMing Wei. In situ X-ray computed tomography (CT) investigation of crack damage evolution for cemented paste backfill with marble waste block admixture under uniaxial deformation. Arabian Journal of Geosciences. 2020; 13 (19):1-16.

Chicago/Turabian Style

Yu Wang; Yonggang Xiao; Zhiqiang Hou; Changhong Li; XiaoMing Wei. 2020. "In situ X-ray computed tomography (CT) investigation of crack damage evolution for cemented paste backfill with marble waste block admixture under uniaxial deformation." Arabian Journal of Geosciences 13, no. 19: 1-16.

Journal article
Published: 09 September 2020 in Journal of Rock Mechanics and Geotechnical Engineering
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Rocks in underground works usually experience rather complex stress disturbance. For this, their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions. The effects of stress disturbances on rock geomechanical behaviors under fatigue loading conditions and triaxial unloading conditions have been reported in previous studies. However, little is known about the dependence of the unloading rate on fatigue loading and confining stress unloading (FL-CSU) conditions that influence rock failure. In this paper, we aimed at investigating the fracture behaviors of marble under FL-CSU conditions using the post-test X-ray computed tomography (CT) scanning technique and the GCTS RTR 2000 rock mechanics system. Results show that damage accumulation at the fatigue stage can influence the final fracture behaviors of marble. The stored elastic energy for rock samples under FL-CSU tests is relatively larger compared to those under conventional triaxial tests, and the dissipated energy used to drive damage evolution and crack propagation is larger for FL-CSU tests. In FL-CSU tests, as the unloading rate increases, the dissipated energy grows and elastic energy reduces. CT scanning after the test reveals the impacts of the unloading rate on the crack pattern and a fracture degree index is therein defined in this context to represent the crack dimension. It shows that the crack pattern after FL-CSU tests depends on the unloading rate, and the fracture degree is in agreement with the analysis of both the energy dissipation and the amount of energy released. The effect of unloading rate on fracture evolution characteristics of marble is revealed by a series of FL-CSU tests.

ACS Style

Yu Wang; Dongqiao Liu; Jianqiang Han; Changhong Li; Hao Liu. Effect of fatigue loading-confining stress unloading rate on marble mechanical behaviors: An insight into fracture evolution analyses. Journal of Rock Mechanics and Geotechnical Engineering 2020, 12, 1249 -1262.

AMA Style

Yu Wang, Dongqiao Liu, Jianqiang Han, Changhong Li, Hao Liu. Effect of fatigue loading-confining stress unloading rate on marble mechanical behaviors: An insight into fracture evolution analyses. Journal of Rock Mechanics and Geotechnical Engineering. 2020; 12 (6):1249-1262.

Chicago/Turabian Style

Yu Wang; Dongqiao Liu; Jianqiang Han; Changhong Li; Hao Liu. 2020. "Effect of fatigue loading-confining stress unloading rate on marble mechanical behaviors: An insight into fracture evolution analyses." Journal of Rock Mechanics and Geotechnical Engineering 12, no. 6: 1249-1262.

Journal article
Published: 06 September 2020 in International Journal of Fatigue
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For rock engineering in cold regions, rock is often subjected to coupled fatigue conditions of freeze-thaw (F-T) and stress disturbance. Rock fracture evolution and energy mechanism under room temperature and constant stress amplitude loading condition have been widely investigated. Yet the rock energy dissipation and damage evolution characteristics subjected to multiple level cyclic loading conditions are not well understood. In this work, multiple level cyclic compressive loading experiments were conducted using GCTS RTR 2000 rock mechanics system on marble with F-T treatment of 0, 20, 40 and 60 cycles. The fracture evolution and energy dissipation mechanism were analyzed as well as the damage evolution characteristics. The results indicate that F-T treatment strongly influences the fatigue mechanical behaviors of marble, with both fatigue strength and strain energy decreases and irreversible volumetric deformation increases with increasing F-T cycles. The incremental rate of dissipated energy becomes faster as cyclic loading level grows. In addition, a F-T-fatigue loads coupling damage variable was proposed by using the input total strain energy and the dissipated strain energy to describe the rock damage evolution after F-T treatment and experiencing fatigue loading. Moreover, a damage evolution model was first established based on the obtained coupling damage variable to describe the two-phase damage accumulation characteristics. Damage accumulation curve presents a first steady increase and then faster increase trend, the damage evolution model can good fit the experimental data.

ACS Style

Y. Wang; S.H. Gao; C.H. Li; J.Q. Han. Energy dissipation and damage evolution for dynamic fracture of marble subjected to freeze-thaw and multiple level compressive fatigue loading. International Journal of Fatigue 2020, 142, 105927 .

AMA Style

Y. Wang, S.H. Gao, C.H. Li, J.Q. Han. Energy dissipation and damage evolution for dynamic fracture of marble subjected to freeze-thaw and multiple level compressive fatigue loading. International Journal of Fatigue. 2020; 142 ():105927.

Chicago/Turabian Style

Y. Wang; S.H. Gao; C.H. Li; J.Q. Han. 2020. "Energy dissipation and damage evolution for dynamic fracture of marble subjected to freeze-thaw and multiple level compressive fatigue loading." International Journal of Fatigue 142, no. : 105927.

Original paper
Published: 27 August 2020 in Geotechnical and Geological Engineering
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In this work, uniaxial fatigue tests combined with post-test X-ray computed tomography (CT) scanning were conducted on marble samples with different interbed orientations, in order to reveal the anisotropic damage evolution characteristics during rock failure. The dynamic elastic modulus, damping ratio, fatigue deformation, damage evolution, accumulative damage modeling and crack pattern were systematically analyzed. The testing results indicate that the interbed structure in marble affects the damage evolution and the associated dynamic mechanical behaviors. The damage curve in “S” style indicates three-stage trend, namely, initial damage stage, steady damage stage and the accelerated damage stage. The damage index during cyclic deformation for marble presents obvious discrepancy. In addition, a fatigue damage prediction models was employed numerically as double-term power equations based on the experimental data. It is found that the selected damage model is suitable in modeling the rapid damage growth in the early and final stage of rock fatigue lifetime. Moreover, post-test CT scanning further reveals the anisotropic damage characteristics of marble, the crack pattern in the fractured sample is controlled by the interbed structure. What is more, the most striking founding is that the fracture degree is in consistent with the damage accumulation within the steady damage stage. Through a series of damage mechanical behavior analysis, the internal mechanism of the effect of interbed orientation on damage evolution of marble is firstly documented.

ACS Style

Y. Wang; S. H. Gao; J. Q. Han. Fatigue-Damage Evolution Characteristics of Interbeded Marble Subjected to Dynamic Uniaxial Cyclic Loads. Geotechnical and Geological Engineering 2020, 39, 855 -870.

AMA Style

Y. Wang, S. H. Gao, J. Q. Han. Fatigue-Damage Evolution Characteristics of Interbeded Marble Subjected to Dynamic Uniaxial Cyclic Loads. Geotechnical and Geological Engineering. 2020; 39 (2):855-870.

Chicago/Turabian Style

Y. Wang; S. H. Gao; J. Q. Han. 2020. "Fatigue-Damage Evolution Characteristics of Interbeded Marble Subjected to Dynamic Uniaxial Cyclic Loads." Geotechnical and Geological Engineering 39, no. 2: 855-870.

Original paper
Published: 16 July 2020 in Geotechnical and Geological Engineering
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The anisotropic characteristics of the P- and S-wave velocity and their velocity–pressure dependency during triaxial deformation are critical in shale gas exploration and development. However, the geomechanical and ultrasonic properties of shale under continuous triaxial deformation are still not well understood. The aim of this work is to experimentally investigate the velocity characteristics of a black shale plugged normal to bedding, parallel to bedding and at 30° and 60° to bedding, under a confining pressure of 5, 20, and 60 MPa, respectively. The in-situ ultrasonic transmission technique during sample deformation was used to reveal the velocity–pressure characteristics of the anisotropic black shale. The experimental results indicate that strength, P- and S-wave velocities, and final failure morphology present obvious anisotropy, and are influenced by the pronounced bedding plane. Before peak strength, the P-wave velocity almost increases with the sample deformation; however, the S-wave velocity first increases and then decreases, which is related to the fracture evolution. The velocity–pressure dependency analysis reveals a different propagation mechanism of ultrasonic wave through shale. Two different kinds of equations were used to fit their relationships and elevated stress. The results suggest that the static geomechanical and ultrasonic properties of black shale are affected by the rock structure and in-field stress level.

ACS Style

Y. Wang; J. Q. Han. Geomechanical and Ultrasonic Characteristics of Black Shale During Triaxial Deformation Revealed Using Real-Time Ultrasonic Detection Dependence Upon Bedding Orientation and Confining Pressure. Geotechnical and Geological Engineering 2020, 38, 1 -22.

AMA Style

Y. Wang, J. Q. Han. Geomechanical and Ultrasonic Characteristics of Black Shale During Triaxial Deformation Revealed Using Real-Time Ultrasonic Detection Dependence Upon Bedding Orientation and Confining Pressure. Geotechnical and Geological Engineering. 2020; 38 (6):1-22.

Chicago/Turabian Style

Y. Wang; J. Q. Han. 2020. "Geomechanical and Ultrasonic Characteristics of Black Shale During Triaxial Deformation Revealed Using Real-Time Ultrasonic Detection Dependence Upon Bedding Orientation and Confining Pressure." Geotechnical and Geological Engineering 38, no. 6: 1-22.

Original contribution
Published: 04 July 2020 in Fatigue & Fracture of Engineering Materials & Structures
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This work aims to investigate the fracture evolution of granite containing two pre‐existing flaws under uniaxial increasing‐amplitude fatigue conditions using macroscopic stress strain descriptions and posttest three‐dimensional (3D) computed tomography (CT) technique. The impacts of flaw arrangement (i.e., approach angle of 20°, 50° and 70°) on the stress strain responses, hysteresis loop shape, damage evolution and crack coalescence pattern at rock bridge segment were investigated. Results show that rock structure has an obvious impact on macroscopic stress strain responses, volumetric strain, dynamic elastic modulus and damping ratio. The sparse‐dense pattern of hysteresis loop is different at each loading stage caused by the differential accumulative damage. The damping ratio increases and dynamic elastic modulus decreases with the increasing fatigue loading stage. Posttest 3D CT visualization reveals a most striking finding that crack coalescence is easy for rock having low approach angle, and complex crack network forms for rock having high approach angle.

ACS Style

Yu Wang; Changhong Li; Jianqiang Han; Huajian Wang. Mechanical behaviours of granite containing two flaws under uniaxial increasing‐amplitude fatigue loading conditions: An insight into fracture evolution analyses. Fatigue & Fracture of Engineering Materials & Structures 2020, 43, 2055 -2070.

AMA Style

Yu Wang, Changhong Li, Jianqiang Han, Huajian Wang. Mechanical behaviours of granite containing two flaws under uniaxial increasing‐amplitude fatigue loading conditions: An insight into fracture evolution analyses. Fatigue & Fracture of Engineering Materials & Structures. 2020; 43 (9):2055-2070.

Chicago/Turabian Style

Yu Wang; Changhong Li; Jianqiang Han; Huajian Wang. 2020. "Mechanical behaviours of granite containing two flaws under uniaxial increasing‐amplitude fatigue loading conditions: An insight into fracture evolution analyses." Fatigue & Fracture of Engineering Materials & Structures 43, no. 9: 2055-2070.

Journal article
Published: 23 June 2020 in Construction and Building Materials
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The deterioration mechanism and fatigue fracturing evolution of granite with two pre-existing flaws experiencing freeze–thaw (F-T) treatment are investigated in this work. The flaws in the rock sample were prepared as a combination of a horizontal flaw with an upper inclined flaw above the horizontal flaw according to the joint characteristics in an open pit slope. In-situ acoustic emission monitoring combined with the post-test 3D computed tomography (CT) technique was employed to reveal the fracture evolution behaviors of rock treated with 0, 50, and 80 freeze–thaw cycles. Results show that the freeze–thaw damage impacts the frost heaving force, cyclic deformation, AE activates, crack coalescence pattern and fatigue life of the granite samples. The accumulative AE count/energy decreases with increasing number of freeze–thaw cycles, and the accumulated AE count/energy in a loading stage gradually grows faster. In addition, AE spectral frequency analysis reveals the impact of previous freeze–thaw damage on the formation of the crack scale, the sample is prone to producing large scale cracks under high freeze–thaw treatment. Moreover, 3D reconstructed CT images present an internal crack network pattern, and the most striking finding is that a simple crack network forms for a sample experiencing high F-T fatigue damage. It is suggested that deterioration of the rock bridge structure is strongly impacted by the accumulative freeze–thaw damage. The testing results are helpful to understand the influence of freeze–thaw and fatigue loading on the fracture evolution characteristics of rock in cold regions.

ACS Style

Y. Wang; J.Q. Han; C.H. Li. Acoustic emission and CT investigation on fracture evolution of granite containing two flaws subjected to freeze–thaw and cyclic uniaxial increasing-amplitude loading conditions. Construction and Building Materials 2020, 260, 119769 .

AMA Style

Y. Wang, J.Q. Han, C.H. Li. Acoustic emission and CT investigation on fracture evolution of granite containing two flaws subjected to freeze–thaw and cyclic uniaxial increasing-amplitude loading conditions. Construction and Building Materials. 2020; 260 ():119769.

Chicago/Turabian Style

Y. Wang; J.Q. Han; C.H. Li. 2020. "Acoustic emission and CT investigation on fracture evolution of granite containing two flaws subjected to freeze–thaw and cyclic uniaxial increasing-amplitude loading conditions." Construction and Building Materials 260, no. : 119769.

Journal article
Published: 16 June 2020 in Theoretical and Applied Fracture Mechanics
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Rock is often subjected to fatigue loads in many mining and civil engineering, rock fatigue mechanical behaviors under constant stress amplitude have been widely investigated. Yet the increasing-amplitude fracture mechanical characteristics of rock and the associated damage evolution model are not well understood. In this work, uniaxial increasing-amplitude fatigue loading experiments were conducted using GCTS RTR 2000 rock mechanics system on marble obtained from an open-pit slope with 0, 20, 40 and 60 freeze-thaw (F-T) cycles. Results show that the previous F-T damage of rock affects the fatigue lifetime, secant modulus, Poisson’s ratio, deformation and damage evolution. The damage accumulation and volumetric deformation increase with the increase of F-T cycles. Damage growth rate becomes weaker with increasing fatigue cyclic levels and a two-stage damage accumulation pattern was found, namely, the initial damage and steady damage stage. The sudden increase moment of stress amplitude has obvious effect on rock damage. Based on the experimental data, a damage evolution model was proposed to describe the two-stage fatigue accumulation characteristics. The model is not only suitable for damage description of each fatigue loading level but also the whole loading process. It is found that the applicability of the damage evolution model is not influenced by the initial damage of rock, and will be applied to intact or jointed rock. The studies in this work are expected to improve the understanding the fatigue damage mechanism of rock subjected to multiple level fatigue loading conditions.

ACS Style

Y. Wang; S.H. Gao; C.H. Li; J.Q. Han. Investigation on fracture behaviors and damage evolution modeling of freeze-thawed marble subjected to increasing- amplitude cyclic loads. Theoretical and Applied Fracture Mechanics 2020, 109, 102679 .

AMA Style

Y. Wang, S.H. Gao, C.H. Li, J.Q. Han. Investigation on fracture behaviors and damage evolution modeling of freeze-thawed marble subjected to increasing- amplitude cyclic loads. Theoretical and Applied Fracture Mechanics. 2020; 109 ():102679.

Chicago/Turabian Style

Y. Wang; S.H. Gao; C.H. Li; J.Q. Han. 2020. "Investigation on fracture behaviors and damage evolution modeling of freeze-thawed marble subjected to increasing- amplitude cyclic loads." Theoretical and Applied Fracture Mechanics 109, no. : 102679.

Journal article
Published: 03 June 2020 in Cold Regions Science and Technology
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This work presents the impacts of freeze-thaw (F-T) fatigue damage on the crack coalescence behaviors at the rock bridge segment for granite samples containing two unparallel flaws. The pre-existing flaw geometry in the rock was a combination of a horizontal flaw and an upper inclined flaw forming a rock bridge structure. In-situ acoustic emission (AE) detection technique and post-test X-ray computed tomography (CT) scanning were used to reveal the rock bridge fracturing characteristics during the whole deformation. Results show that both the F-T cycle and flaw inclined angle influence the crack propagation path, sample strength, deformation and AE pattern and the rock bridge fracture behavior. The AE counts and energy curves present skip phenomenon and are in consistent with the stress drop points on the macroscopic stress-strain curves. The accumulative AE energy and count decrease with increasing F-T cycles. In addition, the cracks during sample failure can be classified into six types by AE spectral frequency analysis, and the high amplitude - low frequency signal was good evident to predict the brittle fracture of the rock bridge. By the post-test CT scanning visualization of the internal crack coalescence pattern at the rock bridge segment, the most striking finding is that the rock bridge structure easily deteriorates for rock subjected to high F-T damage, which suggests that repeated F-T damage drives the crack propagation at the flaw tip and can accelerate the communication of the pre-existing flaws. The testing results are expected to enhance the understanding of the F-T fatigue damage effect on the rock bridge fracturing and can be favorable for predicting the stability of rock structures and rock mass in cold regions.

ACS Style

Y. Wang; W.K. Feng; H.J. Wang; C.H. Li; Z.Q. Hou. Rock bridge fracturing characteristics in granite induced by freeze-thaw and uniaxial deformation revealed by AE monitoring and post-test CT scanning. Cold Regions Science and Technology 2020, 177, 103115 .

AMA Style

Y. Wang, W.K. Feng, H.J. Wang, C.H. Li, Z.Q. Hou. Rock bridge fracturing characteristics in granite induced by freeze-thaw and uniaxial deformation revealed by AE monitoring and post-test CT scanning. Cold Regions Science and Technology. 2020; 177 ():103115.

Chicago/Turabian Style

Y. Wang; W.K. Feng; H.J. Wang; C.H. Li; Z.Q. Hou. 2020. "Rock bridge fracturing characteristics in granite induced by freeze-thaw and uniaxial deformation revealed by AE monitoring and post-test CT scanning." Cold Regions Science and Technology 177, no. : 103115.

Original article
Published: 10 May 2020 in Environmental Earth Sciences
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Underground excavation usually results in the decrease of horizontal stress in the front of the working face, which may trigger the occurrence of rock bust hazards. Examining rock failure under confining pressure unloading conditions is necessary to reveal the fracture mechanism of rock mass subjected to stress disturbance. Although many investigations have studied the rock mechanical behaviors during unloading, the time-lagged triaxial unloading paths on the rock fracturing mechanisms are still poorly understood. Triaxial unloading experiments and the post-test CT scanning technique were conducted on fine-grained marble samples under different unloading conditions. The stress–strain behaviors, energy evolution characteristics, and the fracture pattern of samples were analyzed. The results indicate that obvious features at various stages can be identified from the deformation history curve of the elastic strain energy (Ue), total strain energy (U), and dissipated energy (Ud). U, Ue, and Ud almost all increase with sample deformation at the time duration stage, and the elastic energy and dissipation energy curves slightly decrease and increase again. After the unloading point, the dissipation energy sharply increases and the incremental rate of elastic energy becomes lower. The elastic strain energy increases with the increasing unloading rate for samples at the confining pressure unloading point and failure point, and it is influenced by the time-lag effect of confining pressure. The crack pattern in the CT images depends on the triaxial unloading rate and time effect, which is in good agreement with the energy dissipation and release analysis. The unloading strategy has an effect on the energy conversion during triaxial unloading tests; in other words, energy dissipation and release are dependent on the unloading rate and time.

ACS Style

Y. Wang; Q. H. Zhao; Y. G. Xiao; Z. Q. Hou. Influence of time-lagged unloading paths on fracture behaviors of marble using energy analysis and post-test CT visualization. Environmental Earth Sciences 2020, 79, 1 -20.

AMA Style

Y. Wang, Q. H. Zhao, Y. G. Xiao, Z. Q. Hou. Influence of time-lagged unloading paths on fracture behaviors of marble using energy analysis and post-test CT visualization. Environmental Earth Sciences. 2020; 79 (10):1-20.

Chicago/Turabian Style

Y. Wang; Q. H. Zhao; Y. G. Xiao; Z. Q. Hou. 2020. "Influence of time-lagged unloading paths on fracture behaviors of marble using energy analysis and post-test CT visualization." Environmental Earth Sciences 79, no. 10: 1-20.

Research article
Published: 06 February 2020 in Geofluids
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This work is aimed at investigating the effect of freeze-thaw (F-T) cycle on the crack coalescence behavior for granite samples containing two unparallel flaws under uniaxial compression. The flaw geometry in the samples was a combination of an upper inclined flaw with a horizontal flaw underneath. After the uniaxial compression experiments, macroscopic crack pattern description and the mesoscopic posttest CT imaging were used to reveal the effects of F-T cycle on the crack coalescence morphology at the rock bridge area. Results show that the stress–strain curves present a fluctuating growth trend and stress drop phenomenon becomes weaker with increasing F-T cycles. In addition, three different kinds of cracks (tensile-wing cracks, oblique shear cracks, and antiwing cracks) were observed, and the crack coalescence pattern was influenced by the F-T cycles and approach angle. A mix of tensile and shear failure occurs for the sample subjected to weak F-T treatment, and simple tensile failure occurs for the sample subjected to high F-T treatment. Moreover, CT imaging reveals a crack network pattern at the rock bridge area, and it is found that the fracture degree deceases with increasing F-T cycles and increases with the increasing approach angle. It suggests that the rock bridge area can be easily fractured for the sample subjected to high F-T cycles. Results of this study can provide theoretical foundation for the instability predication of fractured rock structures in cold regions.

ACS Style

Y. Wang; C. H. Li. Investigation on Crack Coalescence Behaviors for Granite Containing Two Flaws Induced by Cyclic Freeze-Thaw and Uniaxial Deformation in Beizhan Iron Mining, Xinjing, China. Geofluids 2020, 2020, 1 -19.

AMA Style

Y. Wang, C. H. Li. Investigation on Crack Coalescence Behaviors for Granite Containing Two Flaws Induced by Cyclic Freeze-Thaw and Uniaxial Deformation in Beizhan Iron Mining, Xinjing, China. Geofluids. 2020; 2020 ():1-19.

Chicago/Turabian Style

Y. Wang; C. H. Li. 2020. "Investigation on Crack Coalescence Behaviors for Granite Containing Two Flaws Induced by Cyclic Freeze-Thaw and Uniaxial Deformation in Beizhan Iron Mining, Xinjing, China." Geofluids 2020, no. : 1-19.

Journal article
Published: 01 February 2020 in International Journal of Fatigue
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To exam the anisotropic deformation and energy evolution characteristics of interbedded marble, cylindrical marble samples cored along angles of 0°, 30°, 60°, and 90° with respect to interbeds were subjected to a triaxial compression experiencing disturbance of the fatigue cyclic-confining pressure unloading (FC-CPU) condition. The triaxial stress disturbance process is divided into three stages: a primary static loading stage, a secondary fatigue cyclic loading stage with the same stress amplitude of 120 MPa, and a confining pressure unloading stage. The deformation, crack pattern and energy conversion were studied using the GCTS RTR 2000 rock mechanical system, post-test X-ray computed tomography (CT) scanning technique, and energy mechanism analysis. Results show that the interbed orientation has an obvious effect on the deformation and crack pattern of marble. Four kinds of crack patterns are revealed from the CT images, and the crack morphology is the simplest for a sample with a 30° orientation. The interbed structure affects the damage accumulation at the fatigue cyclic stage that controls the final failure behavior. The dissipated energy used to drive the crack propagation is relatively large for marble samples undergoing the stress disturbance test compared to those under conventional triaxial tests. The energy dissipation result is in good agreement with the crack pattern, and it is found that the formation of a curved crack consumes much more energy than straight cracks. Through a series of triaxial compression tests under stress disturbance paths, the mechanism of the effect of interbed orientation on fracture behavior and energy evolution of marble are documented.

ACS Style

Y. Wang; W.K. Feng; C.H. Li. On anisotropic fracture and energy evolution of marble subjected to triaxial fatigue cyclic-confining pressure unloading conditions. International Journal of Fatigue 2020, 134, 105524 .

AMA Style

Y. Wang, W.K. Feng, C.H. Li. On anisotropic fracture and energy evolution of marble subjected to triaxial fatigue cyclic-confining pressure unloading conditions. International Journal of Fatigue. 2020; 134 ():105524.

Chicago/Turabian Style

Y. Wang; W.K. Feng; C.H. Li. 2020. "On anisotropic fracture and energy evolution of marble subjected to triaxial fatigue cyclic-confining pressure unloading conditions." International Journal of Fatigue 134, no. : 105524.

Original contribution
Published: 12 January 2020 in Fatigue & Fracture of Engineering Materials & Structures
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The work aims to experimentally investigate the anisotropic fatigue characteristics of marble with different bedding orientations using uniaxial fatigue experiments and posttest computed tomography (CT) scanning. The impacts of interbed orientation on the strength, deformation, fatigue life, and stimulated fracture pattern were systematically analysed. Results show that the axial, lateral, and volumetric strain curves present a three‐stage deformation and are influenced by the interbed orientation. The volumetric strain is maximum and minimum for a marble sample with 30 and 90° orientation, respectively, which is closely related to the failure mode. The crack pattern in the CT images is related to the interbed orientation; the crack density and scale are the largest for a 90° orientation sample and are the smallest for a 30° orientation sample. Good correlation has been established between the fatigue lifetime and the interbed orientation. It is suggested that anisotropic cyclic behaviours of marble is structurally dependent.

ACS Style

Yu Wang; Shaohua Gao; Dongqiao Liu; Changhong Li. Anisotropic fatigue behaviour of interbeded marble subjected to uniaxial cyclic compressive loads. Fatigue & Fracture of Engineering Materials & Structures 2020, 43, 1170 -1183.

AMA Style

Yu Wang, Shaohua Gao, Dongqiao Liu, Changhong Li. Anisotropic fatigue behaviour of interbeded marble subjected to uniaxial cyclic compressive loads. Fatigue & Fracture of Engineering Materials & Structures. 2020; 43 (6):1170-1183.

Chicago/Turabian Style

Yu Wang; Shaohua Gao; Dongqiao Liu; Changhong Li. 2020. "Anisotropic fatigue behaviour of interbeded marble subjected to uniaxial cyclic compressive loads." Fatigue & Fracture of Engineering Materials & Structures 43, no. 6: 1170-1183.

Journal article
Published: 04 November 2019 in Water
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The deterioration of rock geomechanical behaviors subjected to freeze–thaw (F–T) action is a determining factor for rock engineering and rock structures in cold regions. In this work, taking six groups of granite obtained from an open pit mine as the research object, F–T cycle treatment, in-situ AE (acoustic emission) monitoring and ultrasonic detection techniques were performed to experimentally reveal the effects of F–T fatigue damage on the mechanical and acoustic properties of granite. The results indicate that the F–T action impacts the rock’s mesoscopic structure, deformation, strength, P and S-wave velocities, AE pattern and energy release. The accumulated AE counts and accumulated AE energy show a decreasing trend as the F–T cycle increases. The frequency spectrum revealed that the width of the low frequency band decreases and the high frequency band increases with increasing F–T cycles, indicating that there is an increase in large-scale cracks for a sample with high F–T treatment. In addition, energy balance analysis further illustrates the energy dissipation and release mechanism. The energy proportion used to drive the crack propagation is relatively small with high F–T treatment, and the final released energy becomes the minimum. The energy evolution characteristics analyzed by the energy balance approach is in good agreement with AE results. It is suggested that the F–T fatigue damage influences the rock energy storage and release characteristics and the instability of rock in the cold regions.

ACS Style

Yu Wang; Wenkai Feng; Huajian Wang; Jianqiang Han; Changhong Li. Geomechanical and Acoustic Properties of Intact Granite Subjected to Freeze–Thaw Cycles during Water-Ice Phase Transformation in Beizhan’s Open Pit Mine Slope, Xinjiang, China. Water 2019, 11, 2309 .

AMA Style

Yu Wang, Wenkai Feng, Huajian Wang, Jianqiang Han, Changhong Li. Geomechanical and Acoustic Properties of Intact Granite Subjected to Freeze–Thaw Cycles during Water-Ice Phase Transformation in Beizhan’s Open Pit Mine Slope, Xinjiang, China. Water. 2019; 11 (11):2309.

Chicago/Turabian Style

Yu Wang; Wenkai Feng; Huajian Wang; Jianqiang Han; Changhong Li. 2019. "Geomechanical and Acoustic Properties of Intact Granite Subjected to Freeze–Thaw Cycles during Water-Ice Phase Transformation in Beizhan’s Open Pit Mine Slope, Xinjiang, China." Water 11, no. 11: 2309.

Journal article
Published: 11 July 2019 in Geophysical Journal International
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SUMMARY For evaluating the fracturing-related activities in a deep shale formation, it is important to investigate the effect of anisotropy on its geomechanical properties. Many effects have been performed to reveal the strength and deformation anisotropy of shale, however, the influence of bedding planes on the anisotropic energy evolution and velocity-energy dependency are still not well understood, especially under high confinement condition. In this study, triaxial compression tests with a high confining pressure of 60 MPa in combination with real-time ultrasonic detection and post-test CT scanning were performed to the shale samples cored along an angle of 0°, 30°, 60° and 90° with respect to bedding planes. The effect of the bedding orientation on the shale geomechanical, ultrasonic, energy dissipation and energy release characteristics are explored. The experimental results show that shale structural features highly affect the total energy, elastic energy and dissipated energy. The increasing trend of elastic energy shows a slow, fast and slow mode, and the dissipate energy increases rapidly near sample failure. Good correlations have been found among the P- and S-wave velocities and the elastic and dissipated strain energy. The mesostructural changes during deformation are considered to be the primary factor controlling the energy sensitivity to the velocities. CT images further reveal the anisotropic fracture pattern which is in good agreement with energy release and dissipation analysis. The analysis of the strain energy and velocities suggests that the strain energy evolution and fracture anisotropy are bedding orientation dependent.

ACS Style

Y Wang; W K Feng; Z H Zhao; D Zhang. Anisotropic energy and ultrasonic characteristics of black shale under triaxial deformation revealed utilizing real-time ultrasonic detection and post-test CT imaging. Geophysical Journal International 2019, 219, 260 -270.

AMA Style

Y Wang, W K Feng, Z H Zhao, D Zhang. Anisotropic energy and ultrasonic characteristics of black shale under triaxial deformation revealed utilizing real-time ultrasonic detection and post-test CT imaging. Geophysical Journal International. 2019; 219 (1):260-270.

Chicago/Turabian Style

Y Wang; W K Feng; Z H Zhao; D Zhang. 2019. "Anisotropic energy and ultrasonic characteristics of black shale under triaxial deformation revealed utilizing real-time ultrasonic detection and post-test CT imaging." Geophysical Journal International 219, no. 1: 260-270.