Assessment of the impact of railway tunnel lining defects with a long working lifespan on its carrying capacity

Assessment of engineering status of railway tunnels with a long working lifespan causes the necessity of definition of the actual stress-strain state of construction design, taking into account the results of inspection of its engineering status. static analysis of lining in this case is performed by finite elements method. In the article the example of such analysis is given. The tunnel is strengthened by the composite tunnel lining consisting of an inner layer of masonry body and a shotcrete outer layer built while rebuilding operation. In response to the inspection considerable variances of the actual lining concrete power of resistance from design value have been revealed, as well as local destructions of a lining and internal voids. It has been estimated that influence of lining concrete resistance power nonhomogeneity leads to decrease in carrying capacity on average by 17.3%. Consideration of inner and outer defects can reduce the carrying capacity by 2-3 times. While that sort of assessment not always allows to reveal dangerous processes in the considered geotechnical system and to realize effective protection measures promptly. In this case it is reasonable to use information modeling on the basis of BIM technologies. In relation to railway tunnels the further enhancement is needed. The following sequence of engineering status assessment of a tunnel while information modeling is proposed: carrying out essential geotechnical and geophysical researches on the route of a tunnel; tunnel structures monitoring system development and deployment, collection and analysis of data; regular control of a tunnel by the railcar with the measuring station; creation of a tunnel digital model, filling it with data, regular updating and checking calculations; development and implementation of essential repair actions.