Theoretical study of three dimensional face failure mechanism of shallow tunnels in soil

Abstract: During tunnel excavation in soil with TM, either Slurry-Shield or Earth Pressure Balance type, it is of utmost importance assess the pressure to be exerted on the face to ensure the stability of the excavation and control surface deformations. In literature there are reported mostly two-dimensional models that do not consider the spatial nature of the problem. On the other hand, the available three-dimensional proposed mechanisms do not accomplish kinematic constraints, that is, from the point of view of the continuity of the failure surface. The failure condition in the face when the boring is performed by mechanized excavation, can be achieved in two ways: gravitational collapse due to insufficient pressure in the shield or expulsion (upheaval) of the wedge if the pressure applied by the shield machine is very high.