When only a portion of the shield lining structures in a full-line tunnel are overloaded,their bearing and failure characteristics are significantly different from those in the full-line overloaded case.In existing st...When only a portion of the shield lining structures in a full-line tunnel are overloaded,their bearing and failure characteristics are significantly different from those in the full-line overloaded case.In existing studies,one or several segmental lining rings have been studied,with overload applied to selected lining rings to analyze the performance evolution of the lining structures;however,this approach fails to reveal the bearing and failure characteristics of shield lining rings under localized overload.To address this research gap,we employ 3D finite element modeling to investigate the mechanical performance and failure mechanisms of shield segmental linings under localized overload conditions,and compare the results with full-line overload scenarios.Additionally,the impact of reinforcing shield segmental linings with steel rings is studied to address issues arising from localized overloads.The results indicate that localized overloads lead to significant ring joint dislocation and higher stress on longitudinal bolts,potentially causing longitudinal bolt failure.Furthermore,the overall deformation of lining rings,segmental joint opening,and stress in circumferential bolts and steel bars is lower compared to full-line overloads.For the same overload level,the convergence deformation of the lining under full-line overload is 1.5 to 2.0 times higher than that under localized overload.For localized overload situations,a reinforcement scheme with steel rings spanning across two adjacent lining rings is more effective than installing steel rings within individual lining rings.This spanning ring reinforcement strategy not only enhances the structural rigidity of each ring,but also limits joint dislocation and reduces stress on longitudinal bolts,with the reduction in maximum ring joint dislocation ranging from 70%to 82%and the reduction in maximum longitudinal bolt stress ranging from 19%to 57%compared to reinforcement within rings.展开更多
We experimentally tested under radial compressive loads and statistically analyzed rings constructed from spruce wood and reinforced with glass fiber.We used the Weibull distribution in statistical analysis,and tested...We experimentally tested under radial compressive loads and statistically analyzed rings constructed from spruce wood and reinforced with glass fiber.We used the Weibull distribution in statistical analysis,and tested five types of rings including unreinforced and composite reinforced（CR） as wound around the ring,oriented as two layers at angles of 45°,60°,75° and 90° to the column axis.We calculated 95 % reliability of load carrying capacity of the rings by Weibull distribution.The highest load carrying capacity was obtained with CR rings at 60° to the axial axis of the ring.Load carrying capacities of rings at CR90,CR75,CR60 and CR45 were 137,192,215 and 126 %greater,respectively,than unreinforced rings.For unreinforced rings,failures resulted from catastrophic breaking of wood materials.None of the reinforced rings failed catastrophically because the outer surface of the rings was reinforced with glass–epoxy composite fiber.Cracks began at the core of the materials under the composite layer for all specimens and resulted in failure of the rings.展开更多
To satisfy the requirements for the precise formation of large-scale high-performance lightweight components with inner ring reinforcement,a new multidirectional loading rotary extrusion forming technology is develope...To satisfy the requirements for the precise formation of large-scale high-performance lightweight components with inner ring reinforcement,a new multidirectional loading rotary extrusion forming technology is developed to match the linear motion with the rotary motion and actively increases the strong shear force.Its principle is that the radial force and rotating torque increase when the blank is axially extruded and loaded.Through the synergistic action of axial,radial,and rotating motions,the orderly fow of metal is controlled,and the cumulative severe plastic deformation(SPD)of an“uplift-trowel”micro-area is generated.Consequently,materials are uniformly strengthened and toughened.Simultaneously,through the continuous deformation of a punch“ellipse-circle,”a high reinforcement component is grown on the cylinder wall to achieve the high-quality formation of cylindrical parts or the inner-ring-reinforcement components.Additionally,the efective strain increases with rotation speed,and the maximum intensity on the basal plane decreases as the number of revolutions increase.The punch structure also afects the axial extrusion loading and equivalent plastic strain.Thus,the proposed technology enriches the plastic forming theory and widens the application feld of plastic forming.Furthermore,the formed large-scale high-performance inner-ring-stifened magnesium components have been successfully verifed in aerospace equipment,thereby solving the problems of integral forming and severe deformation strengthening and toughening.The developed technology has good prospects for mass production and application.展开更多
基金supported by the National Natural Science Foundation of China(No.52008308).
文摘When only a portion of the shield lining structures in a full-line tunnel are overloaded,their bearing and failure characteristics are significantly different from those in the full-line overloaded case.In existing studies,one or several segmental lining rings have been studied,with overload applied to selected lining rings to analyze the performance evolution of the lining structures;however,this approach fails to reveal the bearing and failure characteristics of shield lining rings under localized overload.To address this research gap,we employ 3D finite element modeling to investigate the mechanical performance and failure mechanisms of shield segmental linings under localized overload conditions,and compare the results with full-line overload scenarios.Additionally,the impact of reinforcing shield segmental linings with steel rings is studied to address issues arising from localized overloads.The results indicate that localized overloads lead to significant ring joint dislocation and higher stress on longitudinal bolts,potentially causing longitudinal bolt failure.Furthermore,the overall deformation of lining rings,segmental joint opening,and stress in circumferential bolts and steel bars is lower compared to full-line overloads.For the same overload level,the convergence deformation of the lining under full-line overload is 1.5 to 2.0 times higher than that under localized overload.For localized overload situations,a reinforcement scheme with steel rings spanning across two adjacent lining rings is more effective than installing steel rings within individual lining rings.This spanning ring reinforcement strategy not only enhances the structural rigidity of each ring,but also limits joint dislocation and reduces stress on longitudinal bolts,with the reduction in maximum ring joint dislocation ranging from 70%to 82%and the reduction in maximum longitudinal bolt stress ranging from 19%to 57%compared to reinforcement within rings.
文摘We experimentally tested under radial compressive loads and statistically analyzed rings constructed from spruce wood and reinforced with glass fiber.We used the Weibull distribution in statistical analysis,and tested five types of rings including unreinforced and composite reinforced（CR） as wound around the ring,oriented as two layers at angles of 45°,60°,75° and 90° to the column axis.We calculated 95 % reliability of load carrying capacity of the rings by Weibull distribution.The highest load carrying capacity was obtained with CR rings at 60° to the axial axis of the ring.Load carrying capacities of rings at CR90,CR75,CR60 and CR45 were 137,192,215 and 126 %greater,respectively,than unreinforced rings.For unreinforced rings,failures resulted from catastrophic breaking of wood materials.None of the reinforced rings failed catastrophically because the outer surface of the rings was reinforced with glass–epoxy composite fiber.Cracks began at the core of the materials under the composite layer for all specimens and resulted in failure of the rings.
基金Supported by National Natural Science Foundation of China(Grant Nos.52075501,51775520)Joint Funds of National Natural Science Foundation of China(Grant No.U20A20230)Shanxi Scholarship Council of China(2021-127).
文摘To satisfy the requirements for the precise formation of large-scale high-performance lightweight components with inner ring reinforcement,a new multidirectional loading rotary extrusion forming technology is developed to match the linear motion with the rotary motion and actively increases the strong shear force.Its principle is that the radial force and rotating torque increase when the blank is axially extruded and loaded.Through the synergistic action of axial,radial,and rotating motions,the orderly fow of metal is controlled,and the cumulative severe plastic deformation(SPD)of an“uplift-trowel”micro-area is generated.Consequently,materials are uniformly strengthened and toughened.Simultaneously,through the continuous deformation of a punch“ellipse-circle,”a high reinforcement component is grown on the cylinder wall to achieve the high-quality formation of cylindrical parts or the inner-ring-reinforcement components.Additionally,the efective strain increases with rotation speed,and the maximum intensity on the basal plane decreases as the number of revolutions increase.The punch structure also afects the axial extrusion loading and equivalent plastic strain.Thus,the proposed technology enriches the plastic forming theory and widens the application feld of plastic forming.Furthermore,the formed large-scale high-performance inner-ring-stifened magnesium components have been successfully verifed in aerospace equipment,thereby solving the problems of integral forming and severe deformation strengthening and toughening.The developed technology has good prospects for mass production and application.
