STUDY OF TUNNEL FACE IN A GRAVEL SITE. PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON NUMERICAL METHODS IN GEOMECHANICS, 11-15 APRIL 1988, INNSBRUCK, AUSTRIA. VOLUMES 1 - 3

This study is related to the finite element computation of the tunnel face of the Lyon subway, which was driven with a slurry pressure shield. The theoretical model of soil behaviour uses only 5 constant parameters which have a physical significance. It allows dilatancy along shearing process. The 3-dimensional computation shows the relation between the slurry pressure at the tunnel face, its displacements, the plastic areas, and the settlement in the open. The field measurements are conducted by inclinometer, tassometer, and by topography. The results are compared to the finite element ones. The amplitudes of the measured displacements compare well with those obtained by calculation. However the direction and distribution of these displacements cannot be modelled accurately by the method used. This emphasizes the major role played by shield-ground interaction, which isn't taken into account in the model. The face "characteristic curve" determined by this method can assess the horizontal stress level which should be applied to the face during excavation. (TRRL)