Analysis of Tunnel Displacements for the Geotechnical Short Term Prediction

Measurement of displacements in tunnels is primarily used for the assessment of the stabilization process and the verification of the system behaviour. In addition the displacement data can be used for the prediction of changing ground conditions ahead of the face. For this purpose, the evaluation of displacement vector orientation turned out to be the most appropriate method. Several authors showed the influence of the excavation on the stress and displacement field when tunnelling through zones of different stiffness. One of the main findings was that the displacement vector orientation significantly changes when the excavation approaches ground with different deformability. Hence, it was concluded that the development of the spatial orientation of the displacement vector can be used for the prediction of the ground conditions ahead of the face. The main results of the investigations performed are summarized in this paper. The evaluation of data from three different case histories is shown in order to encourage the use of advanced displacement data evaluation.