Modelling time-dependent plastic behaviour of geomaterials
- Autores: Fei Song
- Directores de la Tesis: Alfonso Rodríguez Dono (dir. tes.), Antonio Gens Sole (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2021
- Idioma: español
- Materias:
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- Resumen
Representing the time-dependent plastic behaviour of geomaterials is a critical issue in the correct application of tunnelling design techniques such as the convergence-confinement method or numerical modelling. Furthermore, during underground excavations below the water table, the effect of seepage flow cannot be ignored, and the behaviour of the tunnel must be analysed in a coupled hydro-mechanical framework.
The main objective of this thesis is to analyse the response of tunnels excavated in saturated time-dependent plastic rock masses. For this purpose, a time-dependent plastic constitutive model has been developed and implemented in the software CODE_BRIGHT to simulate the time-dependent, strain-softening and creep-induced failure behaviour of geomaterials. Moreover, a coupled hydro-mechanical model is utilised to simulate the interaction between solid deformations and fluid flows. The obtained results provide relevant insights into the response of tunnels excavated in saturated time-dependent plastic rock masses. However, numerical difficulties might occur when modelling multi-stage excavations problems, when considering multi-physics coupled processes or non-linear mechanical material models, especially if the layers or pieces of excavated material are relatively coarse. In order to mitigate these numerical difficulties, a smoothed excavation (SE) method has been proposed and implemented in the software CODE_BRIGHT, which can improve numerical efficiency and mitigate non-convergence issues.
Subsequently, to analyse the stability of tunnels with a combined support system, numerical solutions have been developed for tunnels excavated in strain-softening rock masses, considering the whole process of tunnel advancement, and the sequential installation of primary and secondary support systems. For this purpose, the actual compatibility conditions at both the rock-support interface and the support-support interface are considered. This method provides a convenient alternative method for the preliminary design of supported tunnels.
