A numerical simulation method of shield tunnel excavation is developed to capture the time-dependent deformation behaviour of surrounding soil. The simulation method consists of four parts:(i) an elastic-plastic-visco...A numerical simulation method of shield tunnel excavation is developed to capture the time-dependent deformation behaviour of surrounding soil. The simulation method consists of four parts:(i) an elastic-plastic-viscous constitutive model that can not only reasonably describe the viscous deformation behaviour of soil, but also appropriately calculate the plastic deformation under typical stress paths of excavation;(ii) simulation of main factors related to shield tunnel excavation, including the shield machine, face pressure, lining, grout behavior, and contacts between multiple media;(iii) a simulation procedure for excavation to reflect the process of shield tunnel excavation and achieve reasonable stress and strain fields at the end of the construction stage;(iv) a creep process that is used to investigate the long-term mechanical behaviours of the surrounding soil and tunnel lining. Taking the CK570H tunnel project in Taipei as the background, a numerical simulation is conducted by adopting the developed simulation method. Based on the simulation results, the radial and circumferential stresses acting on the lining, which are induced by the surrounding soil viscosity, are analysed. The rule of the mechanical response of lining, including its deformation, bending moment, and axial force, with time is revealed. On this basis, the long-term safety of the lining is evaluated.展开更多
A new method is presented to develop the existing elastic-plastic constitutive model into an elastic-plastic-viscous one for clays.The actual loading process is divided into an instant process and a delayed process de...A new method is presented to develop the existing elastic-plastic constitutive model into an elastic-plastic-viscous one for clays.The actual loading process is divided into an instant process and a delayed process denoting the elastic-plastic strain and viscous strain, respectively. The elastic-plastic strain is determined by either an elastic-plastic model for overconsolidated clays or an improved model based on the elastic-plastic model for normally consolidated clays. In order to calculate viscous strain, a reference state line is defined based on the actual loading path. Combining the reference state line, an existing elastic-plastic model can be conveniently developed into an elastic-plastic-viscous model. Furthermore, using the proposed method, the modified cam clay model is extended into an elastic-plastic-viscous model. Comparisons with test results demonstrate that the extended model can capture the main time-dependent behaviours of clays, including creep, stress relaxation and strain rate effects.展开更多
In order to consider the stress path dependency of soils,this paper decomposes any arbitrary stress path into several infinitesimal stress paths.Then the infinitesimal stress path is further transformed into the super...In order to consider the stress path dependency of soils,this paper decomposes any arbitrary stress path into several infinitesimal stress paths.Then the infinitesimal stress path is further transformed into the superposition of two parts,i.e..a constant stress ratio part and a constant mean stress part,which arc sufficiently close to the real stress path.T he plastic strain increments under the transformed paths arc determined separately,and then the plastic strain under any path is obtained.Based on the instantaneous loading line of normally consolidated soil,a reference state line is proposed to determine the overconsolidation ratio and creep time of soil.The overconsolidation ratio is introduced into the viscous How rule to obtain the viscous strain increment.The strcss-strain-timc relationship for triaxial compression condition is extended to 3D stress condition by the transformed stress method.The proposed model adopts only seven material parameters and each of them has a clear physical meaning.Comparisons with test results demonstrate that the model can not only reasonably predict the plastic strain under typical stress paths of excavation,but adequately capture the time-dependent behaviours of soils,including creep,stress relaxation and strain rate effect.展开更多
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(Grant No.52025084)the National Natural Science Foundation of China(Grant No.51778026)。
文摘A numerical simulation method of shield tunnel excavation is developed to capture the time-dependent deformation behaviour of surrounding soil. The simulation method consists of four parts:(i) an elastic-plastic-viscous constitutive model that can not only reasonably describe the viscous deformation behaviour of soil, but also appropriately calculate the plastic deformation under typical stress paths of excavation;(ii) simulation of main factors related to shield tunnel excavation, including the shield machine, face pressure, lining, grout behavior, and contacts between multiple media;(iii) a simulation procedure for excavation to reflect the process of shield tunnel excavation and achieve reasonable stress and strain fields at the end of the construction stage;(iv) a creep process that is used to investigate the long-term mechanical behaviours of the surrounding soil and tunnel lining. Taking the CK570H tunnel project in Taipei as the background, a numerical simulation is conducted by adopting the developed simulation method. Based on the simulation results, the radial and circumferential stresses acting on the lining, which are induced by the surrounding soil viscosity, are analysed. The rule of the mechanical response of lining, including its deformation, bending moment, and axial force, with time is revealed. On this basis, the long-term safety of the lining is evaluated.
基金supported by the National Natural Science Foundation of China(Grant Nos.51522802,51778026,51421005&51538001)the Natural Science Foundation of Beijing(Grant No.8161001)。
文摘A new method is presented to develop the existing elastic-plastic constitutive model into an elastic-plastic-viscous one for clays.The actual loading process is divided into an instant process and a delayed process denoting the elastic-plastic strain and viscous strain, respectively. The elastic-plastic strain is determined by either an elastic-plastic model for overconsolidated clays or an improved model based on the elastic-plastic model for normally consolidated clays. In order to calculate viscous strain, a reference state line is defined based on the actual loading path. Combining the reference state line, an existing elastic-plastic model can be conveniently developed into an elastic-plastic-viscous model. Furthermore, using the proposed method, the modified cam clay model is extended into an elastic-plastic-viscous model. Comparisons with test results demonstrate that the extended model can capture the main time-dependent behaviours of clays, including creep, stress relaxation and strain rate effects.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1839201,51778026,51421005&51538001).
文摘In order to consider the stress path dependency of soils,this paper decomposes any arbitrary stress path into several infinitesimal stress paths.Then the infinitesimal stress path is further transformed into the superposition of two parts,i.e..a constant stress ratio part and a constant mean stress part,which arc sufficiently close to the real stress path.T he plastic strain increments under the transformed paths arc determined separately,and then the plastic strain under any path is obtained.Based on the instantaneous loading line of normally consolidated soil,a reference state line is proposed to determine the overconsolidation ratio and creep time of soil.The overconsolidation ratio is introduced into the viscous How rule to obtain the viscous strain increment.The strcss-strain-timc relationship for triaxial compression condition is extended to 3D stress condition by the transformed stress method.The proposed model adopts only seven material parameters and each of them has a clear physical meaning.Comparisons with test results demonstrate that the model can not only reasonably predict the plastic strain under typical stress paths of excavation,but adequately capture the time-dependent behaviours of soils,including creep,stress relaxation and strain rate effect.
