Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact mode...Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact modes are classified into dense contact, local non-contact, and loose contact. Subsequently, the corresponding mechanical model for each contact mode is developed according to its mechanical characteristics using the complex variable method. In the proposed mechanical model, a special algorithm is introduced to detect whether the local non-contact zone is re-contacted. Besides, a novel conformal mapping method is also proposed to accurately calculate the mechanical response of the concrete lining. Finally, the accuracy of the proposed method is verified by comparing it with the finite element method(FEM). Several parameter investigations are conducted to analyze the effects of different contact modes on the rock-lining interaction. The results show that:(i) the height of the local noncontact area does not have a significant effect on the contact stress distribution if no re-contact occurs;(ii) backfill grouting can reduce the local stress concentration caused by poor contact modes;and(iii) reducing the friction coefficient of the interface can lead to a more uniform distribution of internal forces in the concrete lining.展开更多
Particle packing is widely applied in organic pollutant adsorption,catalytic reaction.biomass combustion,nuclear cooling,and other scenarios.Due to the complexity of the shape,the studies on the void fraction of the c...Particle packing is widely applied in organic pollutant adsorption,catalytic reaction.biomass combustion,nuclear cooling,and other scenarios.Due to the complexity of the shape,the studies on the void fraction of the cylindrical particles are not as thorough as the spherical particles.This study investigated the influence of the flling rate,material properties and sphericity on the void fraction of cylinders through experiments and simulation.DEM(discrete element method)was validated by the internal structures of the packing obtained by CT(computed tomography).Based on the logarithmic correlation between the void fraction and flling rate,an ingenious framework for predicting the void fraction of cylindrical particles was presented with two intermediate coefficients.By correlating the coefficients with the material property and sphericity,a novel void-fraction prediction model was established with R-squared of 0.996.The mechanism of void fraction under random loose packing for cylinders was eventually found in this study.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 51738002 and 52108376)Fundamental Research Funds for the Central Universities (Grant No. 2021CZ111)
文摘Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact modes are classified into dense contact, local non-contact, and loose contact. Subsequently, the corresponding mechanical model for each contact mode is developed according to its mechanical characteristics using the complex variable method. In the proposed mechanical model, a special algorithm is introduced to detect whether the local non-contact zone is re-contacted. Besides, a novel conformal mapping method is also proposed to accurately calculate the mechanical response of the concrete lining. Finally, the accuracy of the proposed method is verified by comparing it with the finite element method(FEM). Several parameter investigations are conducted to analyze the effects of different contact modes on the rock-lining interaction. The results show that:(i) the height of the local noncontact area does not have a significant effect on the contact stress distribution if no re-contact occurs;(ii) backfill grouting can reduce the local stress concentration caused by poor contact modes;and(iii) reducing the friction coefficient of the interface can lead to a more uniform distribution of internal forces in the concrete lining.
基金This work was supported by the China National Key R&D Program during the 13th Five-year Plan Period(grant number 2018YFC0705300)the National Natural Science Foundation of China(grant number 52078354).
文摘Particle packing is widely applied in organic pollutant adsorption,catalytic reaction.biomass combustion,nuclear cooling,and other scenarios.Due to the complexity of the shape,the studies on the void fraction of the cylindrical particles are not as thorough as the spherical particles.This study investigated the influence of the flling rate,material properties and sphericity on the void fraction of cylinders through experiments and simulation.DEM(discrete element method)was validated by the internal structures of the packing obtained by CT(computed tomography).Based on the logarithmic correlation between the void fraction and flling rate,an ingenious framework for predicting the void fraction of cylindrical particles was presented with two intermediate coefficients.By correlating the coefficients with the material property and sphericity,a novel void-fraction prediction model was established with R-squared of 0.996.The mechanism of void fraction under random loose packing for cylinders was eventually found in this study.
