Monitoring system for the control of a large embankment close to failure

摘要

The excavation of an exploratory adit through the foundations of a 30 m high embankment at the southern entry of the Mont Blanc road tunnel led to substantial deformations of the portion of fill located directly above the trial adit. Since the embankment was originally formed as an uncontrolled disposal of muck from the Mont Blanc tunnel and not subjected to any construction control, the event brought the outer edge of the embankment into a state of incipient failure. In view of the importance of the embankment which, beyond customs and service areas, incorporates the Mont Blanc tunnel ventilation-intake as well as administrative buildings, a detailed site investigation was carried out and the whole area was instrumented and subject to continuous electronic monitoring of deformations, displacements and pore pressures of the soil foundations. Displacements and deformations were measured both on the ground surface and at depth. The data collected through the monitoring programme are presented with the aim to provide some information on the response of the embankment, foundation soils and groundwater table to the extensive and differentiated remedial measures which were undertaken for stabilizing the embankment toe. Some consideration is also given to the instrumentation itself which, allowing for an immediate return and interpretation of the data, made it possible to follow the behaviour of the embankment during execution of the remedial works on a real-time basis and, subsequently, to assess the impact of the completed works in terms of improvement of stability.