Reinforcing Distressed Lining Structure of Highway Tunnel with Bonded Steel Plates: Case Study

Lining cracks are one of the most common distresses in in-service highway tunnels and pose severe threats to the safety of tunnel operation. Traditional methods for retrofitting distressed tunnel lining all have limitations, and the inner-surface reinforcing method using bonded steel plates is becoming increasingly popular. However, research into its use for reinforcing the distressed lining of highway tunnels is limited. This paper intends to fill this knowledge gap by presenting a case study of using bonded steel plates for strengthening the cracked lining of highway tunnels. First, the cracking status of tunnel lining was thoroughly analyzed through field investigation. It is found that water-induced swelling and softening of surrounding rock increases the overburden pressure on the structure and an aging effect accelerates the degradation of the lining concrete, finally causing the cracking of the tunnel lining. Second, the thickness, width, and spacing of bonded steel plates that have a significant effect on the reinforcing performance were studied numerically by FLAC3D software. It is found that bonded steel plates with a thickness of 8 mm, a width of 30 cm, and spacing of 20 cm can achieve optimum reinforcing performance. Finally, the field implementation scheme for reinforcing the cracked tunnel is proposed accordingly. (C) 2019 American Society of Civil Engineers.