During the pre-bidding stage for the construction of the undersea tunnel for the ambitious Mumbai Ahmedabad High Speed Rail (MAHSR), at least seven Indian companies have expressed their interest for the works, said officials. The National High Speed Rail Corporation Limited (NHSRCL) told media sources that seven Indian companies had participated in the pre-bid meeting for constructing the undersea tunnel of the corridor. NSHRCL also said that the tender for the construction of the tunnel has been floated and bids are invited till 19 February 2021. The bullet train project will have a 21 km long underground corridor from Bandra Kurla Complex (BKC) to Kalyan Shilphata in Maharashtra. NSHRCL said that about 7 km of this underground corridor is under the Thane creek. Out of this, a 1.8 km stretch will be developed under the sea bed, while the remaining part of the section is to be built under the mangroves marshland on either side of the creek. The tender has been floated for tunnel development, which includes testing and commissioning for the double-line high-speed railway for the project using a tunnel boring machine (TBM) and a New Austrian Tunnelling Method (NATM).4th Indian Cement Review Conference 202117-18 March Click for event info A geotechnical investigation of the undersea tunnel area was carried out earlier by a team of engineers from Japan's Kawasaki Geological Engineering firm, NHSRCL, and Rail India Technical and Economic Service Ltd (RITES). In order to study the sea bed structure, a static refraction technique (SRT) survey was carried out by the team, involving firing a high energy sound wave towards the seabed from beneath the water surface as well as mapping the refracted sound wave to determine the density of the rock under the sea bed. Also read: Mumbai-Ahmedabad bullet train gets environmental clearanceImage Source