For the operation of driverless trains, a tunnel boring machine would be drilled under the Chetpet lake to build tunnels. Now, CMRL has started soil tests on the lake beds. For a depth of 35m or 120 feet, 2 bore holes would be drilled on the bottom of this lake and samples would be collected. The type of machinery that would be used for tunneling would be decided by the samples.
The superb piece of information is that 2 metro stations at Chetpet and Kilpauk would be linked by the twin tunnels that would be constructed under the lake. By 2026, the 3 corridor phase-2 metro rail project would be completed and it would cover a distance of 118.9kms.
On Wednesday, 30th November 2022 workers were busy drilling through the bottom of the lake. It must be noted that a pontoon platform carrying a drilling rig was seen floating on the lake.
The type and elasticity of the soil samples would be determined by a geologist. The soil strength properties would be studied in the lab. By this, a clear picture would be got about the number of men and machines that would be needed for drilling.
It is learnt that in the phase-2 metro rail project CMRL is building twin tunnels under the water bodies in 2 locations namely Adyar river and Chetpet lake. This would be on corridor 3 from Madhavaram Milk Colony and Siruseri Sipcot of 45.8km.
From the second week of December, tunneling work under the Adyar river would start and this was according to an official belonging to CMRL. It is noteworthy that at Chetpet shaft building work to deploy and retrieve tunnel boring machines has started and the metro station entry/exit points. It is revealed that the twin tunnels would be nearly 30m in depth in KMC and 22m depth in Chetpet.
The sandstone soil present at Chetpet area would make the tunneling a little easier. In areas like Thirumayilai and Thiruvanmiyur etc, the soil tests have shown that the soil present there was charnockite rock. Water pressure would be more in the water bodies and hence tunnelling work there would be challenging.