Abstract:

The loss convergence displacement is induced by the constructing procedure of the monitored section and tunnel. And it is of great value to identification of the deformation state and evaluation of stability of surrounding rock mass. Application of experiential analogy method is considered lacking in reliability due to the challenging condition of surrounding rock mass. And the consistency in the evolving rule of convergence displacement obtained by the three-dimensional simulation and field monitoring is not universal. So it should be discussed before application of the mechanical parameters back analysis methods based on convergence curves. But so far the consistency in total convergence displacement can be ensured. Based on this premise, a method of obtaining loss displacement is presented, in which the Hoek experiential formula is applied and some provisions in specification are cited as the support. Finally this method was carried out in the analysis of deformation rule of surrounding rock mass in Auxiliary Tunnel A and B in Jinping II Power Station. The final monitored displacement, loss displacement, total convergence displacement and relative convergence displacement are obtained. And the good agreement of the fitting curves with the monitored ones shows that this method is rational in obtaining the evolving rule of displacement of surrounding rock mass with the space effect. Furthermore, this method is an important foundation for the evaluation of stability of surrounding rock mass and the back analysis of mechanical parameters.

Key words: loss convergence displacement, convergence curves, field monitoring, back analysis, consistency