2019 Volume 19 Issue 1 Pages 1_1-1_20
In order to propose an estimation formula for damage rates of water distribution pipes, the damage to water distribution pipelines caused by the Great East Japan Earthquake (formally the 2011 Touhoku-taiheiyo-oki Earthquake) is analyzed based on the database of pipeline network and damage to the pipes prepared by the Sendai City Waterworks Bureau.
Influences of topographical classification, pipe material and diameter to the water pipe damages are firstly analyzed. A damage rate defined by the number of damage occurrences per unit length (km) is utilized as a damage index in this paper. As a result of the analyses, the topographical classification is found to be the most influential factor among all. The damage rate of the artificially cut-and-fill grounds (mostly used as residential districts) is almost three times large as compared to that of the alluvium (flat) grounds. Furthermore, it is found that thickness of the fill and/or distance between the damage location and cut-and-fill boundary strongly affect the damage rate. Namely, the depth of fill from 3 to 7 m and the distance from 10 to 20 m (fill side) show the highest damage rate.
The relationship between the damage rates and surface ground motions (velocities) is analyzed in the same way, and a standard damage rate curve is established, that gives the damage rates in the alluvium (flat) grounds at some surface ground velocities.
Based on the result of the analyses, this paper describes a proposed estimation formula for the damage rates of water distribution pipes due to earthquakes.
