Pipe Profiling Using Digital Image Correlation

Pipes are among the important components of the U.S. infrastructure. Deflection monitoring of gravity pipes, such as culverts or sewer pipelines, provides an invaluable information of the pipe’s structural condition to the decision makers. Conventionally, laser profilers are used for dry pipes to accurately measure their profile. However, laser profilers are very expensive, cumbersome to transport, and they require an expert to operate. Digital image correlation (DIC) is an inexpensive alternative to the conventionally used laser profilers to measure the pipe’s profile and consequently its deflection accurately over time. In this paper, feasibility of DIC for pipe profiling is investigated and verified through several linear variable differential transformers (LVDTs) and cable displacement sensors (CDSs). Two 5.5-ft long, 60-in. circular corrugated metal pipes (CMPs) and one equivalent size arch CMP were embedded, instrumented and subjected to static load using an MTS hydraulic actuator under the laboratory condition. The inside of two circular CMPs were lined by a polymeric spray applied pipe lining (SAPL) to investigate the effect of liner brittle failure (i.e., cracking) on the accuracy of DIC. The pipes were loaded until the ultimate bearing capacity of the composite system was reached. The profiles of pipe samples were measured before, after and during the loading to calculate their respective deflections using DIC. In this study, MATLAB and a commercially available software, GOM Correlate, were used to obtain the pipe samples’ profile. The result shows an excellent agreement between DIC, LVDTs, and CDSs. It is recommended that potential use of DIC in the actual field conditions be investigated for laser profiler substitution.