To study the damage mechanisms of anhydrite rock under freeze-thaw cycles, the physicalmechanical properties and the microcracking activities of anhydrite rock were investigated through mass variation, nuclear magneti...To study the damage mechanisms of anhydrite rock under freeze-thaw cycles, the physicalmechanical properties and the microcracking activities of anhydrite rock were investigated through mass variation, nuclear magnetic resonance, scanning electron microscope tests, and uniaxial compression combined with acoustic emission(AE) tests. Results show that with the increase of freeze-thaw processes,the mass, uniaxial compression strength, and elastic modulus of the anhydrite specimens decrease while the porosity and plasticity characteristics increase.For example, after 120 cycles, the uniaxial compression strength and elastic modulus decrease by 46.54% and 60.16%, and the porosity increase by 75%. Combined with the evolution trend of stressstrain curves and the detected events, three stages were labeled to investigate the AE characteristics in freeze-thaw weathered anhydrite rock. It is found that with the increase of freeze-thaw cycles, the proportions of AE counts in stage Ⅰ and stage Ⅱ show a decaying exponential trend. Contrarily, the proportion of AE counts in stage Ⅲ displays an exponential ascending trend. Meanwhile, as the freeze-thaw cycles increase, the low-frequency AE signals increase while the intermediate-frequency AE signals decrease. After 120 cycles, the proportion of low-frequency AE signals increases by 168.95%, and the proportion of intermediate-frequency AE signals reduces by 81.14%. It is concluded that the microtensile cracking events occupy a dominant position during the loading process. With the increase of freeze-thaw cycles, the b value of samples decreases.After 120 cycles, b value decreases by 27.2%, which means that the proportion of cracking events in rocks with small amplitude decreases. Finally, it is proposed that the freeze-thaw damage mechanism of anhydrite is also characterized by the water chemical softening effect.展开更多
A simple testing method for secondary or induced stress of surrounding rockwas presented by laboratory experiment, numerical simulation and in situ testing based onthe basic principle of the historical stress restorin...A simple testing method for secondary or induced stress of surrounding rockwas presented by laboratory experiment, numerical simulation and in situ testing based onthe basic principle of the historical stress restoring method.First, stress equivalent coefficient,which key coefficient of stress restored testing, was obtained by laboratory experiment.Second, experimental results were examined using 3D finite element numericalanalysis and the influence factors were analyzed by 2D finite element numerical analysis.The correctness of induced stress measuring results in situ for highway tunnel wereproved by elastic mechanics theory solution and single-hole stress rescission method.Thenew simple method of induced stress measuring has important practical value for undergroundengineering induced stress field analysis.展开更多
Combined with highway construction, the analysis on the relationship betweentunnel construction and coal resource exploitation was processed, which was based onthe research of rational exploitation depth of coal.3D FE...Combined with highway construction, the analysis on the relationship betweentunnel construction and coal resource exploitation was processed, which was based onthe research of rational exploitation depth of coal.3D FEM numerical analysis for tunnelexcavation was carried out according to engineering geological features of coal measurestrata in the project area.Based on the analysis of displacement and stress of the surroundingrock in the tunnel after excavation, the characteristics for displacement andstress of the tunnel support structure were analyzed when the underlying coal bed wasexploited with sublevel and full caving method.In addition, combined with the related codeand standard, the economic and safe prohibiting exploited depth of the underlying coalbed was proposed, so that a scientific basis for tunnel construction of coal measure strataand reasonable exploitation of the mineral resources in complex geological conditions canbe offered.展开更多
基金the Fundamental Research Funds for the Central Universities(Project No.2022CDJKYJH037)the National Key R&D Program of China(Grant No.2021YFB3901402)。
文摘To study the damage mechanisms of anhydrite rock under freeze-thaw cycles, the physicalmechanical properties and the microcracking activities of anhydrite rock were investigated through mass variation, nuclear magnetic resonance, scanning electron microscope tests, and uniaxial compression combined with acoustic emission(AE) tests. Results show that with the increase of freeze-thaw processes,the mass, uniaxial compression strength, and elastic modulus of the anhydrite specimens decrease while the porosity and plasticity characteristics increase.For example, after 120 cycles, the uniaxial compression strength and elastic modulus decrease by 46.54% and 60.16%, and the porosity increase by 75%. Combined with the evolution trend of stressstrain curves and the detected events, three stages were labeled to investigate the AE characteristics in freeze-thaw weathered anhydrite rock. It is found that with the increase of freeze-thaw cycles, the proportions of AE counts in stage Ⅰ and stage Ⅱ show a decaying exponential trend. Contrarily, the proportion of AE counts in stage Ⅲ displays an exponential ascending trend. Meanwhile, as the freeze-thaw cycles increase, the low-frequency AE signals increase while the intermediate-frequency AE signals decrease. After 120 cycles, the proportion of low-frequency AE signals increases by 168.95%, and the proportion of intermediate-frequency AE signals reduces by 81.14%. It is concluded that the microtensile cracking events occupy a dominant position during the loading process. With the increase of freeze-thaw cycles, the b value of samples decreases.After 120 cycles, b value decreases by 27.2%, which means that the proportion of cracking events in rocks with small amplitude decreases. Finally, it is proposed that the freeze-thaw damage mechanism of anhydrite is also characterized by the water chemical softening effect.
基金Supported by the National Natural Science Foundation Special Originality Innovation Research Colony of China(50621403)
文摘A simple testing method for secondary or induced stress of surrounding rockwas presented by laboratory experiment, numerical simulation and in situ testing based onthe basic principle of the historical stress restoring method.First, stress equivalent coefficient,which key coefficient of stress restored testing, was obtained by laboratory experiment.Second, experimental results were examined using 3D finite element numericalanalysis and the influence factors were analyzed by 2D finite element numerical analysis.The correctness of induced stress measuring results in situ for highway tunnel wereproved by elastic mechanics theory solution and single-hole stress rescission method.Thenew simple method of induced stress measuring has important practical value for undergroundengineering induced stress field analysis.
基金Supported by the National Natural Science Foundation Special Originality Innovation Research Colony of China(50621403)
文摘Combined with highway construction, the analysis on the relationship betweentunnel construction and coal resource exploitation was processed, which was based onthe research of rational exploitation depth of coal.3D FEM numerical analysis for tunnelexcavation was carried out according to engineering geological features of coal measurestrata in the project area.Based on the analysis of displacement and stress of the surroundingrock in the tunnel after excavation, the characteristics for displacement andstress of the tunnel support structure were analyzed when the underlying coal bed wasexploited with sublevel and full caving method.In addition, combined with the related codeand standard, the economic and safe prohibiting exploited depth of the underlying coalbed was proposed, so that a scientific basis for tunnel construction of coal measure strataand reasonable exploitation of the mineral resources in complex geological conditions canbe offered.
