"One of the main functions of the TBM is to resist underground water pressure while it passes through aquifers. TBM "Chundee" may have had malfunctioned and allowed water to seep in, triggering the catastrophe that has affected scores of houses and rendered hundreds homeless,” said a tunnelling expert.

https://timesofindia.indiatimes.com/city/kolkata/data-from-tbm-black-box-key-to-find-operational-lapses/articleshow/71016768.cms