OKAYAMA – Chunks of mortar were found Monday on the Sanyo Shinkansen Line tracks inside a tunnel in Kasaoka, Okayama Prefecture, West Japan Railway Co. said.
Electrical engineers of a JR West affiliate found 12 chunks, weighing about 50 kg in total, in the tunnel at around 12:25 a.m., the railway said.
The fragments were found about 1 km from the eastern end of the approximately 2.7-km tunnel, and they had apparently fallen from a seam in a 3.5-meter-high wall. The largest fragment measured 40 cm by 24 cm and weighed some 7 kg, according to the railway.
Most of the chunks were found next to the tracks, although some were on the tracks, it added.
The carrier said the incident will have no effect on the bullet train line, which connects Shin-Osaka Station in Osaka Prefecture and Hakata Station in Fukuoka Prefecture.
The railway said it suspects water eroded the wall. It scraped off the mortar around the seam and checked the condition of the entire tunnel wall before allowing trains to run on their normal schedule.
In 1999, JR West found pieces of concrete from tunnel walls on the shinkansen line. In July that year, the carrier discovered more than 2,000 weak points in the walls of 93 tunnels on the line in western Japan — points it described as being “not sufficiently attached” to the walls.
However, no problems were found in the Kasaoka tunnel when it was checked for cracks at the time, according to JR West. Another visual check conducted last year also showed no irregularities, it said. Company officials added that they would recheck all JR West tunnels for similar problems as quickly as possible.
“Even if concrete pieces were to fall onto the tracks, the trains are equipped with devices to knock the fragments away, and so would not affect their running,” a JR West official said.