SAFETY EVALUATION OF OLD-STANDARD RIGID PVC PIPES WITH ADHESIVE JOINTS IN THE EVENT OF FAULT DISPLACEMENT

Many old telecommunication pipes built during the 1960s and 1970s are still in use in Japan.Past earthquake surveys have found that old-standard rigid polyvinyl chloride (PVC) pipes with adhesive joints are vulnerable to earthquakes, and it appears that such pipes were damaged by fault displacement during the 2016 Kumamoto earthquake.However, the safety of old-standard rigid PVC pipes in the event of fault displacement has not been evaluated.The present study evaluated the safety of old-standard PVC pipes in the event of fault displacement in finite element analysis.First, an analysis model of a pipe with an adhesive joint was developed in the numerical analysis of a bending test.An analysis model of the soil-pipe interaction was then developed in a numerical analysis of a soil-tank test.It was confirmed that the results of the bending test and the soil-tank test were accurately reproduced using the developed model.After confirming that the analysis results agree well with experimental results, a numerical analysis of the safety evaluation in the event of fault displacement was conducted.The results showed that when the joint center was located 300 mm from the fault plane where the maximum principal stress occurs and when the fault plane is perpendicular to the pipes, the yielding occurred with the smallest fault displacement of 55 mm for the new pipe and only 25 mm for removed pipes.The analysis showed that even a small displacement may cause serious damage to the old-standard rigid PVC pipes with an adhesive joint.