Hideki Omuro, Tomokazu Himono
Papers # 2018 Las-Vegas
In Japan, polyethylene (PE) pipe have been used for a long time, but its usage is limited for water service (low density PE / PE 50) and gas service (medium density PE / PE 80). However, after Hyogoken Nanbu Earthquake in 1995, it started to sell PE pipes for water distribution applications, because no damage on PE pipes at the earthquake was highly evaluated. In addition, long-term durability was also evaluated, and 31,700 km PE pipes for water distribution have been installed until 2015.
The main futures of PE pipe are two points, 1) pipes and fittings using a high-performance polyethylene material "PE 100", 2) pipes and fittings are formed by an integral structural by electro-fusion (EF) joints.
The "PE100" material developed in the late 1980s has many advantages for underground pressure pipeline, e.g. flexibility, impact resistance, anti-crack propagation performance and long-term durability. With respect to flexibility, in particular, the tensile yield strain is 8% or more, which is much larger than that of a metal material, and almost no deterioration in strength is caused by tension and compression until yield. In addition, both pipes and fittings can be provided of the same polyethylene material. We think that the characteristics of monolithic pipeline and the flexibility can absorb the ground distortion due to the earthquake. We have verified the characteristics of PE pipeline from the viewpoint of seismic performance. 1) Basic characteristics (tensile, compression and repeated elongation), 2) Real scale simulated test, 3) Evaluating pipeline after actual earthquake. We measured strain distribution of pipe deformation by actual scale experiment simulating ground crack and unequal settlement. We selected hydrostatic pressure performance for the evaluating pipe and fittings through the real earthquake. As the result, we found that it has high earthquake resistance performance.
Also, we were investigating PE pipeline damages after actual earthquakes, e.g. 2007 Niigata Chuetsu-oki Earthquake, 2011 the Great East Japan Great Earthquake, 2016 Kumamoto earthquake. There is no damage by ground deformation, seismic motions and liquefaction, except for extreme cases like tsunami and ground collapse. From the above, we can confirm that polyethylene pipe has high earthquake resistance. Furthermore, it has a superiority of long life and economic efficiency