To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxi...To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxial compression tests.The ejection and failure during compression process of phyllites are monitored in real-time by high-speed camera system.The results demonstrate that the phyllites with different bedding angles all consistently follow the linear energy storage and dissipation(LESD)law during compression.The ultimate energy storage of phyllites with varying bedding angles can be calculated precisely via using the LESD law.Based on this,four kinds of energy-based rockburst indices are applied to quantitatively assess the burst proneness for phyllites.Combined with the recorded images of high-speed camera system,ejection distance,and mass of rock fragments and powder,the burst proneness for phyllites with various bedding angles is qualitatively evaluated adopting the far-field ejection mass ratio.Next,burst proneness of anisotropic phyllites is assessed quantitatively and qualitatively.It is found that phyllites with bedding angles of 0°,15°,and 90°have a high burst proneness,and that with bedding angle of 30°has a medium burst proneness,whereas the ones with bedding angles of 45°,60°,and 75°have a low burst proneness.Finally,the published experimental data of shale and sandstone specimens with different bedding angles are extracted,and it is preliminarily verified that the bedding angle does not change the LESD law of rocks.展开更多
Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alte...Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alternating loads can be regarded as multi-stage constant-amplitude cyclic loads following simplification.In this paper,the mechanical responses and acoustic emission(AE)characteristics of red sandstone with five bedding dip angles(0°,30°,45°,60°,and 90°)under such loads are investigated,and the damage evolution processes of the five specimens are revealed from both quantitative and microscopic perspectives.The results show that the fatigue deformation characteristics of the specimens are affected by the bedding dip angle.Under cyclic loads,the axially irreversible plastic deformations of the rocks increase,their elastic stiffness increases,their crack volumetric strain increases and then decreases,and their AE cumulative count/energy curves exhibit a ladder shape.A damage evolution model based on the crack volumetric strain is proposed,and the damage evolution process is divided into two stages:a rapid increase stage and a tendency toward stabilization stage.Through cluster analysis,the AE events are used to classify the damage into three categories:small-sized localized damage,large-sized tensile damage,and large-sized shear damage.Finally,the MohreCoulomb criterion is applied to analyze the relationship between the failure modes of the red sandstone specimens and the dip angle of the bedding.The results of this study will help to predict the stability and safety of compressed air energy storage reservoirs in abandoned coal mines.展开更多
To determine the acoustic wave propagation characteristics of bedded shales under different confining pressures and temperatures,shales from the Longmaxi Formation in the Sichuan Basin are taken as research objects.Ba...To determine the acoustic wave propagation characteristics of bedded shales under different confining pressures and temperatures,shales from the Longmaxi Formation in the Sichuan Basin are taken as research objects.Based on ultrasonic experiments,the acoustic wave prop-agation properties of shales with different bedding angles are investigated.The effects of the confining pressure,temperature,and bedding angle on the acoustic velocity,attenuation coefficient,and acoustic anisotropy coefficient are analyzed.Based on the results,an acoustic velocity prediction model for bedded shales considering the confining pressure,temperature,and bedding angle is established.The experiments show that,for confining pressures from 0 to 50 MPa and temperatures from 20 to 100 ℃,the acoustic velocity of the shales increases with increasing confining pressure and decreases with increasing temperature and bedding angle.The attenuation coefficient of the shales exhibits a decreasing trend with increasing confining pressure,but increases with increasing temperature and bedding angle.The acoustic anisotropy coefficient of shale gradually decreases with increasing confining pressure,but increases with increasing temperature and bedding angle.The acoustic velocity prediction model for in-situ bedded shales established in this study has a high level of accuracy.The relationship between the acoustic anisotropy coefficient and the bedding angle is satisfied by a binomial equation.The relationship between the acoustic anisotropy coefficient and the confining pressure and temperature follows a binary linear logarithmic equation.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42077244).
文摘To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxial compression tests.The ejection and failure during compression process of phyllites are monitored in real-time by high-speed camera system.The results demonstrate that the phyllites with different bedding angles all consistently follow the linear energy storage and dissipation(LESD)law during compression.The ultimate energy storage of phyllites with varying bedding angles can be calculated precisely via using the LESD law.Based on this,four kinds of energy-based rockburst indices are applied to quantitatively assess the burst proneness for phyllites.Combined with the recorded images of high-speed camera system,ejection distance,and mass of rock fragments and powder,the burst proneness for phyllites with various bedding angles is qualitatively evaluated adopting the far-field ejection mass ratio.Next,burst proneness of anisotropic phyllites is assessed quantitatively and qualitatively.It is found that phyllites with bedding angles of 0°,15°,and 90°have a high burst proneness,and that with bedding angle of 30°has a medium burst proneness,whereas the ones with bedding angles of 45°,60°,and 75°have a low burst proneness.Finally,the published experimental data of shale and sandstone specimens with different bedding angles are extracted,and it is preliminarily verified that the bedding angle does not change the LESD law of rocks.
基金supported by the National Natural Science Foundation of China(Grant No.52374078)the Fundamental Research Funds for the Central Universities(Grant No.2023CDJKYJH021)the Sichuan-Chongqing Science and Technology Innovation Cooperation Program Project(Grant No.2024TIAD-CYKJCXX0011).
文摘Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alternating loads can be regarded as multi-stage constant-amplitude cyclic loads following simplification.In this paper,the mechanical responses and acoustic emission(AE)characteristics of red sandstone with five bedding dip angles(0°,30°,45°,60°,and 90°)under such loads are investigated,and the damage evolution processes of the five specimens are revealed from both quantitative and microscopic perspectives.The results show that the fatigue deformation characteristics of the specimens are affected by the bedding dip angle.Under cyclic loads,the axially irreversible plastic deformations of the rocks increase,their elastic stiffness increases,their crack volumetric strain increases and then decreases,and their AE cumulative count/energy curves exhibit a ladder shape.A damage evolution model based on the crack volumetric strain is proposed,and the damage evolution process is divided into two stages:a rapid increase stage and a tendency toward stabilization stage.Through cluster analysis,the AE events are used to classify the damage into three categories:small-sized localized damage,large-sized tensile damage,and large-sized shear damage.Finally,the MohreCoulomb criterion is applied to analyze the relationship between the failure modes of the red sandstone specimens and the dip angle of the bedding.The results of this study will help to predict the stability and safety of compressed air energy storage reservoirs in abandoned coal mines.
基金funded by the National Natural Sci-ence Foundation of China(42272190)the Sichuan Provincial Natural Science Foundation of China(2022NSFSC1065)the National College Student Innovation and Entrepreneurship Training Program(202210615030).
文摘To determine the acoustic wave propagation characteristics of bedded shales under different confining pressures and temperatures,shales from the Longmaxi Formation in the Sichuan Basin are taken as research objects.Based on ultrasonic experiments,the acoustic wave prop-agation properties of shales with different bedding angles are investigated.The effects of the confining pressure,temperature,and bedding angle on the acoustic velocity,attenuation coefficient,and acoustic anisotropy coefficient are analyzed.Based on the results,an acoustic velocity prediction model for bedded shales considering the confining pressure,temperature,and bedding angle is established.The experiments show that,for confining pressures from 0 to 50 MPa and temperatures from 20 to 100 ℃,the acoustic velocity of the shales increases with increasing confining pressure and decreases with increasing temperature and bedding angle.The attenuation coefficient of the shales exhibits a decreasing trend with increasing confining pressure,but increases with increasing temperature and bedding angle.The acoustic anisotropy coefficient of shale gradually decreases with increasing confining pressure,but increases with increasing temperature and bedding angle.The acoustic velocity prediction model for in-situ bedded shales established in this study has a high level of accuracy.The relationship between the acoustic anisotropy coefficient and the bedding angle is satisfied by a binomial equation.The relationship between the acoustic anisotropy coefficient and the confining pressure and temperature follows a binary linear logarithmic equation.
