F. Deleruyelle

Analytical modelling of a deep tunnel in a viscoplastic rock mass accounting for a simplified life cycle and extension to a particular case of porous media

Abstract An analytical approach to the viscoplastic behaviour of a rock mass around a deep tunnel in different stages of a simplified life cycle is presented. The viscoplasticity is modelled by means of a simple (linear) Norton–Hoffs law. First, the solution for a dry rock mass is presented, then an extension to a particular case of a porous saturated rock mass with a Poissons ratio of 0.5 is examined. Some numerical examples are carried out to show the consistency and relevance of the solutions. Parametric studies illustrate the influence of key parameters such as rock mass viscosity and time of lining emplacement. This analytical approach constitutes a useful reference to test more complex numerical simulation and makes it possible to obtain practical estimations of the poromechanical behaviour of underground structures.

Hydromechanical Postclosure Behavior of a Deep Tunnel Taking into Account a Simplified Life Cycle

AbstractThis paper addresses the hydromechanical postclosure behavior of an underground long cylindrical deep tunnel drilled into a massif (host medium) and backfilled at the end of its service life. It is concerned with the development of quasi-analytical Laplace transform solutions based on a simplified life cycle of the tunnel, idealized in four stages: (1) excavation, (2) pore-pressure dissipation before lining installation, (3) lining installation and tunnel exploitation, and (4) postclosure. The solutions proposed in this paper therefore extend the previous work of the authors, in this case by explicitly taking into consideration the excavation, waiting for lining installation, and tunnel exploitation stages of the life cycle. Results from a parametric study are also presented to highlight the hydromechanical responses of the tunnel over periods of its life cycle. The accuracy and correctness of the solutions from a finite-element model have been verified with the quasi-analytical results. The prese...

Influence of Microcracking of Host Rock on the Hydromechanical Responses of Underground Structures: Constitutive Modeling and Numerical Simulations

This paper presents a numerical modeling accounting for the effect of cracking on both mechanical and hydraulic properties of unsaturated rocks. Firstly, the constitutive model developed by Bui, et al. [3], established in the framework of thermodynamics of porous media, is recalled. Its main feature is that damage intervenes on both mechanical behavior and hydraulic properties (water retention curve and hydraulic conductivity). Secondly, the model is validated against experimental data on an argillaceous rock. Finally, this constitutive model is implemented into a domestic finite element code to study numerically the evolution of hydromechanical responses of a radioactive waste underground gallery during a simplified life cycle. Numerical simulations demonstrate the consistency of the model and highlight the influence of desaturation on the hydromechanical behavior of the gallery.

Analytical approach to the creep and hydromechanical couplings around underground cavities

This paper deals with the time-dependent behavior of rocks in the vicinity of underground cavities. Our approach is analytical and addresses different stages of the life cycle of a cavity. The theoretical framework is taken up from previous works [1-4] and completed to account for an irreversible viscoplastic behavior, which has been experimentally evidenced [5-9]. Other attempts to account for creep are available in the literature. Some of them use the viscoplasticity theory [10-14 for instance]. Most often, they require numerical tools. However, analytical approaches are useful to check the consistency of more complex numerical simulation and to make it possible to obtain practical estimations of the behavior of underground structures. To our knowledge, Pouya [13] provided an approximate analytical solution in the case of an unlined tunnel accounting for a monophasic rock mass obeying to a Norton-Hoff’s creep law in the particular case of incompressible elasticity (ඃ烟 = 0.5). Cosenza et al. [14] analytically dealt with the long-term behavior of a spherical cavity inside a saturated poro-viscoplastic rock mass in the borderline case of stationary state, neglecting the transitional stages. In this paper, an analytical solution is developed in the case of a monophasic, then porous saturated, rock mass accounting for a linear version of the Norton-Hoff’s creep law. Owing to the complexity of the hydromechanical couplings encountered in the poromechanical part, only the elastically incompressible case (ඃ烟 = 0.5) will be presented; the general case, in which the Poisson’s ratio can take any value, leads to much more complex developments. 2. General framework of the problem