”2m hole in the sidewalk”... What caused the ground to disappear in Incheon Central Park?

It has been revealed that the collapse that occurred in Songdo International City Central Park in Incheon, South Korea, was caused by a leak in an underground water supply pipe.
According to the Incheon Facilities Corporation on the 17th, a collapse occurred on the sidewalk in Central Park in Songdo-dong, Yeonsu-gu at 10:30 a.m. the previous day.
The corporation is working to drain the puddle that was created by the collapse, measuring 1.5 to 2 meters in diameter, and has begun to investigate the cause of the accident.
As a result of the investigation, it was found that the water supply pipes buried 3 meters underground
It was confirmed that the connection point had ruptured, causing a water leak and an outflow of soil and sand. This water pipe is connected to the public toilets in Central Park. The underground section under the park's sidewalk
A public corporation official said, "It appears that the screws connecting the pipes came loose, causing the water to leak. For now, we are working on repairs to the water supply pipes and on restoration work."
Previously, water leaks due to burst water pipes occurred a total of three times on roads in the Matsushima 1 and 3 construction areas between June and the 5th of this month.
Incheon city believes that the water pipe burst due to multiple factors, including soil salinity, and is carrying out extensive repair and reinforcement work.
It is being planned.