Assessment service state of tunnel structure

Structural assessment is one of the key activities in maintaining the performance of a tunnel during its service life. The lining structure of tunnel is subjected to both external loads and environmental effects. The service states of the structure are its current behavior under combined actions during long-term service. To quantitatively assess the structural performance of tunnel lining, its service states are illuminated in the principle of limit state design as Suitable, Degraded, Deteriorated, Unavailable, and Unstable. Taking into account the complexity of a tunnel in service, data collected from inspection are categorized as structural condition and operating condition. Registered structural defects represent the symptoms of structural conditions, while investigation of operating condition includes verifying external loads and environmental effects. Framework of assessment procedure is proposed to carry out sequentially with structural components, portions of lining, and then whole lining structure. A case of a road tunnel is presented to illustrate the applicability of the proposed approach. (C) 2011 Published by Elsevier Ltd.