ANÁLISE DE DESLOCAMENTOS MEDIDOS COM CONVERGÊNCIOMETRO DE HASTE NO TÚNEL SABUGAL-MEIMOA

Hydraulic small diameter rock mass tunnelling, using an open shield TBM, have circular cross section and usually offer favourable conditions in terms of stability. Based on the evidence gathered during the excavation of the Sabugal–Meimoa tunnel, the displacements measured with a stem convergenciometer are analysed. The tunnelling went through a metassedimentary rock mass, geologically and geotechnically heterogeneous, and to cope with this the project foresaw the existence of four distinct geotechnical zones, each with a specific primary support aiming to ensure the stability of the excavation. Given the theoretical curves of convergence-confinement of rock masses, maximum displacements were measured in respect to the rock mass quality, primary support, distance ahead of excavation and the time to onset of the reading, in order to obtain comparable results. The analysis was performed using multivariate analysis tools such as data correlation matrix (CM), principal component (PCA) and factor of correspondences analyses (FCA). It became possible to verify that there are no relations between the measured displacements and the different rock mass quality or the different type of primary support applied. Neither are there observed obvious relations between the maximum displacements registered and the distance ahead of the excavation or days elapsed until the beginning of the monitoring.