AN ANALYSIS OF 3-DIMENSIONAL GROUND MOVEMENTS - THE THUNDER-BAY TUNNEL

A three-dimensional (3D) elastoplastic finite-element analysis, which is capable of simulating the advance of a tunnelling shield and the associated ground losses resulting from the tunnelling process, is used to calculate the deformations caused by the excavation of the Thunder Bay sewer tunnel. The soil parameters adopted in the analysis were based on the results determined from stress-dependent triaxial tests. The results of this analysis are compared with the measured soil displacements. Reasonable agreement between the calculated and observed 3D settlement distribution and horizontal displacements at different distances from the tunnel face is reported. This overall agreement for displacements under 3D conditons suggests that the method of analysis may be applicable to design problems involving tunnelling in soft clays similar to that at the Thunder Bay sewer tunnel provided that the soil parameters are reliably determined.