A MODEL FOR SWELLING ROCK IN TUNNELING

In this paper, the phenomenon of swelling in tunnelling will be treated as a hydraulic-mechanical coupled process. This approach allows one to model the observed floor heaves realistically, i. e. without the prediction inevitable in the previous models of movements at the tunnel crown and walls. Furthermore, the development of heave and pressure over the course of time can be studied. The absence of deformations above the floor level is here interpreted as a consequence of the hydraulic boundary conditions. Besides the importance of seepage flow, the influence of rock strength is illustrated. Swelling rock is considered as an elastoplastic material. This allows one to predict the often large heaves of a tunnel floor as observed in situ. According to the numerical results, the area of practically relevant swelling strains extends as far as the plastic zone.