Crack is one of the most common lining deteriorations, which is generally regarded as an indicator of tunnel safety. The present study investigated the lining cracks of 11 tunnels which are 200 km away from the Longmenshan fault zone. In order to evaluate the seismic capacity of these tunnels with longitudinal cracks in the permanent lining, a modified deformation-based pseudo-static assessment method was developed. The propagation of lining cracks was simulated by a reconstructed damaged plasticity constitutive model of reinforced concrete. The analyses adopted a two-dimensional finite element model and took tunnel depth, initial crack position, and the interaction between soil and lining structures into account. The analysis results showed that the modified evaluation method could simulate the damage process of lining structures under the action of seismic shear wave well. The results also showed that the failure modes of tunnels with cracked permanent lining were different with different burial depth in an earthquake. The cracks in the spandrel had the greatest impact on the seismic capacity of tunnels and should be reinforced in time before the earthquake. In addition, the interaction between the temporary support and permanent lining had little effect on the damage process of linings but had an impact on the damage speed. This study can provide a reference for the safety assessment of cracked lining tunnels in seismically active areas and help to determine the reinforcement measures and time more reasonably.

Introduction

A large number of tunnels have been built in the mountainous areas of western China. In the past 10 years, seismic activity in this area, including four intensive earthquakes: the 2008 Wenchuan Earthquake (Ms = 8.0), 2010 Yushu Earthquake (Ms = 7.1), 2013 Lushan Earthquake (Ms = 7.0) and 2017 Jiuzhaigou Earthquake (Ms = 7.0). Although underground structures are generally considered to be more seismic-resistant than overground structures, some relevant literature shows that tunnels can be damaged in strong earthquakes (Asakura, 1997; Shen et al., 2014; Wang et al., 2001; YASHIRO and KOJIMA, 2007). Therefore, as an important part of transportation infrastructure, the seismic performance of tunnels in seismically active areas is still an important issue. Tunnels generally satisfy the seismic design requirements in a long period after the construction. However, the time-dependent deterioration of rock masses and lining structures are sometimes inevitable, which may lead to degradation in operational tunnels, such as cracks, leakage and spalling. Lining cracks are the most common tunnel anomalies, which are frequently regarded as one of the indicators of tunnel safety (Asakura and Kojima, 2003; Richards, 1998; Yuan et al., 2012). Cracks bring leakage, carbonization, and corrosion to the concrete structure, and even destroy the structural integrity, leading to spalling and collapse.