Ahmedabad Metro: TBM Launch without Diaphragm Wall in Ahmedabad Subway Metro Project, first time in India

Ahmedabad :  Ahmedabad Metro Project is going to be inaugurated soon. For the first time in Ahmedabad subway metro project  (Ahmedabad Underground Metro Project) Tunnel Boring Machines (TBM) have been launched without Diaphragm Wall. This alternative method, which has been used for the first time in the country in this metro project, has helped speed up the construction of the Kankaria metro station. This method was used for the first time in India in a metro project.  Previously, this method was used in Istanbul Metro.

In the Ahmedabad Metro underground project, Afcons Infrastructure Ltd is constructing two underground stations, twin tunnels totaling 3.5 km, a cut and cover section and a ramp connecting the elevated and underground sections.  Headwall construction stalled due to delay in transfer of land for Kankaria station. During this period the first TBM which was ready to be commissioned could not start up to speed.  To reduce project delays and speed up work, the project team adopted a new method of TBM tunneling at Kankaria station without D-wall.

In top-down construction method, station box D-wall is constructed before TBM tunnelling. But it was not possible at Kankaria station. Hence this innovative method was adopted. The width of the station was increased from 20 meters to 22 meters to accommodate the TBM. Informing about this new method, project manager S Nakkiran said, tunnels were started for both eastbound and westbound lanes. Therefore, the work of TBM was started from the launching shaft.  The tunnels of both the lines were completed smoothly with construction of permanent rings and then the TBM was taken out at Kalupur station. To ensure proper functioning of the TBM, the team also developed an in-house calibration unit for the earth pressure sensor.  Sometimes, when the sensor is covered with mud, the sensor’s earth pressure function is hampered.  

Parallel construction method was adopted instead of sequential method to speed up the work at Kankaria station. So  Construction of the main station box was completed four months ahead of schedule and construction of the Over Track Exhaust (OTE) duct was completed five months ahead of schedule.  Gujarat Metro Rail Corporation has also appreciated these efforts, he added.


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