Hydromechanical modelling of shaft excavation in Meuse/Haute-Marne laboratory

This paper presents a numerical modeling of hydromechanical response of a vertical shaft subjected to excavation in hard clay called argillite. The excavation procedure of the shaft is first presented. Based on experimental data obtained in conventional laboratory tests, a unified plastic and viscoplastic model is used to describe poromechanical behavior of the argillite in saturated and unsaturated conditions. This model takes into account the main features of poromechanical behavior of the material such as non-linear yield surface, non-associated plastic flow, sensitivity to water saturation, instantaneous and time-dependent plastic deformations. The model’s parameters are determined from experimental data obtained in triaxial compression tests and triaxial creep tests. The proposed model is implemented in a fully coupled finite element computer code in order to perform numerical modeling of boundary values problems. The numerical simulation of the shaft is then presented in the second part. Evolutions of displacement and pore pressure are evaluated during the excavation and compared with in situ measurement. It is shown that the hydromechanical responses of rock are affected by drying process inside the shaft. However, the influence of creep deformation seems to be negligible due to the relatively short duration of excavation.