Fiber Optic Method for Buried Pipelines Health Assessment after Earthquake-Induced Ground Movement-2nd phase

The central part of the project, method validation testing was performed at The Cornell Large-Scale Lifelines Testing Facility, the NEES site at Cornell University (Cornell NEES Site). The aim of the testing was to validate the researched method for reliable, real-time, automatic or on-demand, assessment of pipelines subject to earthquake-induced permanent ground displacement. Beside this primary aim, the testing helped evaluate the performance of the deployed distributed sensors in close-to-real conditions. The second phase of the test was performed in June 2011.

Description of the test basin
The Cornell NEES Site contains a large test basin in which a pipeline can be assembled and tested under simulated permanent ground displacement (PGD). The basin is a 3.40 m wide, 13.40 m long, and 2.0 m deep steel-frame box with wooden walls. It consists of two parts: the movable north part and the fixed south part. To limit the amount of soil that has to be placed inside the basin, four “shoulders” were constructed at the north and south end of the basin. The geometry of the shoulders was designed so that their presence does not affect the expected soil behavior as well as the test execution itself. Furthermore, these shoulders were used as working areas while burying and excavating the pipeline.

For each test, a segmented concrete pipeline specimen was assembled in the basin and covered with the soil. The movable north part of the test basin was attached to four hydraulic actuators which were anchored in massive concrete counter bearings. During the test, the hydraulic actuators were used for controlled movement of the north part of the basin. The joint between the two parts was designed in that way, that a transverse fault oriented 50 degree relative to the longitudinal length of the basin can be simulated.

Description of the pipeline specimen used in the second test
The pipeline specimen used in the second test consisted of five 2.36 m (7 ft. 9 in.) long segments (as installed), assembled using 30.5 cm long (12 in.) bell-and-spigot joints sealed by grout. The inner and outer diameters of the pipe body were 30.5 cm (12 in.) and 40.6 cm (16 in.) respectively, while the outer diameter at the joint was 50.8 cm (20 in.). Short segment of the pipe was added at the movable (north) extremity in order to provide for mechanical connection with the frontal and rear walls of the basin, as in the case of the first test. In the second test all the pipe segments had the same mechanical properties. They were built of fiber reinforced concrete by NEESR Award partner (Purdue University in the frame on his research). The uniform mechanical properties along the pipeline made the results of the second test different from those obtained in the first test.