Deformation during service stage is monitored by periodical inspection and countermeasures are performed as needed in road tunnel. Cracks over permanent lining and the heaving of road surface often occur, however, it is difficult to assess the development of such deformation features from data acquired during construction and service stages.

The deformation mechanism and the effect of countermeasure are discussed through the result from in-situ measurement and numerical analysis in this paper. First, the tunnel lining was observed through up-close visual inspection for five years. One horizontal and one vertical boring were done to investigate the ground characteristics in the road surface area where the heavy heaving was observed. In addition, the condition of permanent tunnel lining and the ground behind it were checked and rock material tests were performed on the bored cores. Next, the development of deformation was simulated by numerical analysis, its mechanisms were examined and the effect of inverted arch concrete was discussed.

As a result, the relation between tunnel deformation and the occurrence of defects is examined with the data by boring. In addition, the mechanism of tunnel deformation when the characteristics of ground indicated a swelling condition, and the relation between the load acting on tunnel lining and the behavior of countermeasure are also clarified. Furthermore, the change in the displacement depth in ground and its effect on tunnel deformation was examined on the basis of in-situ measurements.

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