The mishap occured when Gurusubramanian was on duty at the first lignite mine, where a giant bucket-wheel excavator was removing sand. He alone was at the spot where the sand caved in, they said.
The victim's body was recovered after nearly a two-hour long operation and sent to the NLC Hospital in Neyveli Town in the district.
A case has been registered by police.
AITUC NLC unit President Kuppusamy alleged that the incident exposed lack of safety measures and has demanded a probe into it.