The Times of India has reported that The Mumbai Metro Rail Cooperation (MMRC) has begun tunnelling below the Mithi river for Metro Line 3.
The 153m tunnel is dug using the New Australian Tunnelling Method (NATM) between Dharavi and Bandra-Kurla Complex (BKC), with the new BKC station below the river.
“The BKC Metro station, that will come up below Mithi river will have two island platforms instead of one island platforms and is being constructed at the other 25 underground stations,” MMRC project director S K Gupta told the Times of India.
“The presence of soil and weak rock under the riverbed increases the risk of instability of the excavated opening before proper support is installed,” added Gupta.
Layers of soil and broken rocks under the riverbed will be strengthened by grouting to reduce permeability and the ingress of water. An ‘umbrella’ of steel bars will be created above the excavation area for safety, and there will be a constant check on the soil/rocks during excavation, the Times of India has reported.
The 33.5km long Line 3 on Mumbai Metro 3 will have 26 underground stations and and a total of 17 TBMs will be used to excavate the new route.