Behaviour of a tunnel face reinforced by bolts: Influence of the soil/bolt interface

The design of reinforced structures requires a perfect knowledge of the behaviour of the soil, the bolts and of the soil/bolt interface. To determine the frictional law between the soil and the bolt, full scale pull-out tests were performed on radial anchor bolts, equipped with strain gauges. The analytical method developed by [Bourdeau, 1994] allows to derive the local frictional law parameters (assumed constant along the rod) from the global relationship between the total load and the head displacement. This frictional law is introduced in a 3D tunnel model with reinforced face. The 3D numerical model provides an accurate geometrical description of the runnel structure, such as the lining behind the face, as well as the interface law between bolts and ground. To observe the influence of the soil/bolt interface, we study the influence of several frictional laws in terms of face displacements and axial forces in the bolts.