Mechanical Performance Study of Pipe-Liner Composite Structure Based on the Digital Image Correlation Method

Repair of reinforced concrete drainage pipes is often performed using polyethylene (PE) lining. To investigate the bearing capacity characteristics of a repaired composite structure, this study conducted experiments on three groups, namely, PE pipes, reinforced concrete pipes, and composite-reinforced concrete PE pipes (count = 9). The cracking and ultimate loads of the three groups under plate loads were evaluated and analyzed. A displacement monitoring method based on two-dimensional digital image correlation (2-D-DIC) and three-dimensional digital image correlation (3-D-DIC) techniques is proposed, and the quantitative laws of strain distribution at the end face of the specimen are obtained. Furthermore, the damage mechanism of the reinforced concrete pipe and the interface spalling damage mechanism of the composite-reinforced concrete PE under load were investigated to reveal the effect of PE lining improvement on the bearing capacity of the reinforced concrete pipe. The maximum deviation of the specimen vertical displacement results obtained using the new noncontact 3-D-DIC method is 2.6% compared with that of the traditional physical sensor method, and this method can successfully capture the deformation and strain data of the target specimen. Therefore, the noncontact DIC method has a broad application prospect in municipal pipeline early warning monitoring systems.