Newly built tunnels often encounter a series of defects within the first few years of operation.If not promptly addressed and reinforced,these defects threaten the tunnel's durability and stability and bring sever...Newly built tunnels often encounter a series of defects within the first few years of operation.If not promptly addressed and reinforced,these defects threaten the tunnel's durability and stability and bring severe challenges to its safe operation.This study aims to explore reinforcement techniques for addressing defects in newly built tunnels.The research begins with an analysis of common defects found in newly built tunnels,followed by a case study of the Jinfeng Tunnel in Chongqing,examining the post-construction defects.The actual reinforcement strategies and methods employed for the tunnel are then discussed.Finally,based on the research findings,this study provides insights and references for tunnel operation and construction units in China,aiming to enhance the overall quality of tunnel engineering in the country,align with sustainable development goals,and promote further improvements at a macro level.展开更多
The influence of initial strain state on the dynamic response of an end bearing pile embedded in isotropic saturated soil is investigated through the linearized theory of small elastic perturbation superposed on large...The influence of initial strain state on the dynamic response of an end bearing pile embedded in isotropic saturated soil is investigated through the linearized theory of small elastic perturbation superposed on largely stressed bodies. The governing equations for soil, based on Blot＇s poroelasticity theory, are derived in the cylindrical coordinates, and the pile is modeled by using the one-dimensional elastic theory. The analytical solutions of pile impedance, frequency response of both twist angle and time history of velocity response are obtained by using of separation of variables technique. Finally, a parametric study of the influence of initial strains on the torsional impedance, twist angle, and velocity response at the top of the pile is carried out.展开更多
A numerical method is used to model a capsule migration in a microchannel with small Reynolds number Re = 0.01. The capsule is modeled as a liquid drop sur- rounded by a neo-Hookean elastic membrane. The numer- ical m...A numerical method is used to model a capsule migration in a microchannel with small Reynolds number Re = 0.01. The capsule is modeled as a liquid drop sur- rounded by a neo-Hookean elastic membrane. The numer- ical model combines immersed boundary with lattice Boltz- mann method （IB-LBM）. The LBM is used to simulate fixed Cartesian grid while the IBM is utilized to implement the fluid-structure interaction by a set of Lagrangian moving grids for the membrane. The effect of shear elasticity and bending stiffness are both considered. The results show the significance of elastic modulus and initial lateral position on deformation and morphological properties of a circular cap- sule. The wall effect becomes stronger as the capsule ini- tial position gets closer to the channel wall. As the elastic modulus of membrane increases, the capsule undergoes less pronounced deformation and velocity in direction x is de- creased, thus, the capsule motion is slower than the back- ground flow. The best agreement between the present model and experiments for migration velocity takes place for the capsule with normal to moderate membrane elastic modulus. The results are in good agreement with experiment study of Coupier et al. and previous numerical studies. Therefore, the IB-LBM can be employed to make prediction in vitro and in vivo studies of capsule deformation.展开更多
A mathematical model of dynamic processes in a composite plate of prestressed piezoelectric(PE)and piezomagnetic(PM)layers is proposed.It is assumed that the initial strain state in the components of the plate is unif...A mathematical model of dynamic processes in a composite plate of prestressed piezoelectric(PE)and piezomagnetic(PM)layers is proposed.It is assumed that the initial strain state in the components of the plate is uniform and is induced by the action of initial mechanical stresses.In the quasi-static approximation,problems of shear horizontally polarized surface acoustic waves(SH-SAW)propagation in a PE/PM plate made of prestressed materials are considered.It is assumed that the materials of the plate layers in their natural state(NS)have symmetry class 6 mm.The adhesion conditions are satisfied at the interface between the layers.The external surfaces of the heterostructure are in contact with the vacuum and are free from mechanical stress.Depending on the nature of the electrical and magnetic conditions specified on the external surfaces,four types of problems are considered.Using the example of a problem with electrically closed and magnetically open conditions on the external surfaces of a PZT-5H/CoFe_(2)O_(4) plate,the features of the influence of the nature and magnitude of the initial mechanical effects on the velocities of SH waves are investigated.The possibility of changing the velocity characteristics of SAWs due to the initial mechanical effects is shown.The results are presented in dimensionless parameters and may be of significant interest for optimizing the structure of new materials in the development and design of devices and equipment operating on SH-SAW.展开更多
Within the framework of the linearized theory of electroelastic wave propagation,a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a sy...Within the framework of the linearized theory of electroelastic wave propagation,a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered.The ferroelectric LiNbO_(3) is used as the main material of the structure.The initial deformed state of the coating material is homogeneous,induced by the action of initial mechanical stresses and an external electrostatic field,the properties of the coating continuously change in thickness.By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface,the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied.The separate and combined effects of initial actions on changes in the physical properties of the structure,the transformation of the surface wave field,and the change in the SAW velocities in a wide frequency range is studied.The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures,in the optimization and design of new structures and devices on SAW with high performance characteristics.展开更多
文摘Newly built tunnels often encounter a series of defects within the first few years of operation.If not promptly addressed and reinforced,these defects threaten the tunnel's durability and stability and bring severe challenges to its safe operation.This study aims to explore reinforcement techniques for addressing defects in newly built tunnels.The research begins with an analysis of common defects found in newly built tunnels,followed by a case study of the Jinfeng Tunnel in Chongqing,examining the post-construction defects.The actual reinforcement strategies and methods employed for the tunnel are then discussed.Finally,based on the research findings,this study provides insights and references for tunnel operation and construction units in China,aiming to enhance the overall quality of tunnel engineering in the country,align with sustainable development goals,and promote further improvements at a macro level.
基金supported by the National Natural Science Foundation of China(No.10632040)
文摘The influence of initial strain state on the dynamic response of an end bearing pile embedded in isotropic saturated soil is investigated through the linearized theory of small elastic perturbation superposed on largely stressed bodies. The governing equations for soil, based on Blot＇s poroelasticity theory, are derived in the cylindrical coordinates, and the pile is modeled by using the one-dimensional elastic theory. The analytical solutions of pile impedance, frequency response of both twist angle and time history of velocity response are obtained by using of separation of variables technique. Finally, a parametric study of the influence of initial strains on the torsional impedance, twist angle, and velocity response at the top of the pile is carried out.
文摘A numerical method is used to model a capsule migration in a microchannel with small Reynolds number Re = 0.01. The capsule is modeled as a liquid drop sur- rounded by a neo-Hookean elastic membrane. The numer- ical model combines immersed boundary with lattice Boltz- mann method （IB-LBM）. The LBM is used to simulate fixed Cartesian grid while the IBM is utilized to implement the fluid-structure interaction by a set of Lagrangian moving grids for the membrane. The effect of shear elasticity and bending stiffness are both considered. The results show the significance of elastic modulus and initial lateral position on deformation and morphological properties of a circular cap- sule. The wall effect becomes stronger as the capsule ini- tial position gets closer to the channel wall. As the elastic modulus of membrane increases, the capsule undergoes less pronounced deformation and velocity in direction x is de- creased, thus, the capsule motion is slower than the back- ground flow. The best agreement between the present model and experiments for migration velocity takes place for the capsule with normal to moderate membrane elastic modulus. The results are in good agreement with experiment study of Coupier et al. and previous numerical studies. Therefore, the IB-LBM can be employed to make prediction in vitro and in vivo studies of capsule deformation.
基金grant from the Russian Science Foundation(Project No.24-29-00773).
文摘A mathematical model of dynamic processes in a composite plate of prestressed piezoelectric(PE)and piezomagnetic(PM)layers is proposed.It is assumed that the initial strain state in the components of the plate is uniform and is induced by the action of initial mechanical stresses.In the quasi-static approximation,problems of shear horizontally polarized surface acoustic waves(SH-SAW)propagation in a PE/PM plate made of prestressed materials are considered.It is assumed that the materials of the plate layers in their natural state(NS)have symmetry class 6 mm.The adhesion conditions are satisfied at the interface between the layers.The external surfaces of the heterostructure are in contact with the vacuum and are free from mechanical stress.Depending on the nature of the electrical and magnetic conditions specified on the external surfaces,four types of problems are considered.Using the example of a problem with electrically closed and magnetically open conditions on the external surfaces of a PZT-5H/CoFe_(2)O_(4) plate,the features of the influence of the nature and magnitude of the initial mechanical effects on the velocities of SH waves are investigated.The possibility of changing the velocity characteristics of SAWs due to the initial mechanical effects is shown.The results are presented in dimensionless parameters and may be of significant interest for optimizing the structure of new materials in the development and design of devices and equipment operating on SH-SAW.
基金This work was performed with a financial support of the Ministry of Science and Higher Education of the Russian Federation(project 01201354242)Russian Foundation of Basic Research(projects 19-08-01051,19-01-00719).
文摘Within the framework of the linearized theory of electroelastic wave propagation,a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered.The ferroelectric LiNbO_(3) is used as the main material of the structure.The initial deformed state of the coating material is homogeneous,induced by the action of initial mechanical stresses and an external electrostatic field,the properties of the coating continuously change in thickness.By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface,the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied.The separate and combined effects of initial actions on changes in the physical properties of the structure,the transformation of the surface wave field,and the change in the SAW velocities in a wide frequency range is studied.The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures,in the optimization and design of new structures and devices on SAW with high performance characteristics.
