ABSTRACT
One of the main problems in underground excavations regarding geotechnical monitoring, especially when excavated with drill and blast, is the late installation of the instruments, namely convergence’s sections. Due to the applied construction methods, the minimum distance, defined on Monitoring and Observation Plans, to which the convergence profiles must be installed, is usually exceeded. This situation has been repeatedly alerted by the Designers, who refer the loss of information of early and main deformations. A methodology for estimating convergences from the excavation instant to the beginning of the convergences readings is presented, by mathematical modelling of time-history convergence data. The proposed approach is applied to a case study in the North of Portugal: the 1346 m length and 7.4 m diameter Access Tunnel in the Venda Nova III Hydroelectric Scheme. An attempt to correlate these results with the RMR and Q was made. This approach can be used both in the construction phase and in the design phase, to predict the behavior of deformations and optimize production cycles and rock supports.
