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  Total Convergences Modelling in Tunnelling a tool for Designers and Contractors

  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 timehistory convergence data. The proposed approach is applied to a case study in the North of Portugal (a 1346 m length and 7.4 m diameter tunnel, excavated in a granitic rock mass). 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 behaviour of deformations and optimize production cycles and rock supports.

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