Metro starts work on walls for tunnels

As tunneling work for metro rail is about to begin in a couple of months, Chennai Metro Rail has started setting up units to make pre-cast concrete tunnel walls at Muttukadu, Tiruneermalai and Vanagaram. Underground tunnels of metro rail will be reinforced with concrete walls which will shore up the tunnels as it passes underneath busy roads and buildings across the city. These walls will be made in segments using specially designed moulds and will be transported to work site so that they can be installed simultaneously when machines start boring. The machine will bore a particular length, then the pre-cast walls will be installed in the bored portion before the machine resumes work. A senior official of metro rail said 12 sets of pre-cast segment moulds have arrived after they were factory-tested in China and Korea. "One set has six cast moulds. The tunnel walls will be made of six pre-manufactured concrete segments. These segments will be interlocked and installed when a machine completes boring a particular length of the tunnel," he added. Metro rail has started work to build diaphragm walls to lower tunnel boring machines at Egmore, Washermanpet, Shenoy Nagar, May Day Park and Kilpauk Medical College. Two tunnel boring machines, which have arrived from China, will be lowered at Washermanpet and Shenoy Nagar where diaphragm walls will be completed earlier than other locations. More machines are expected to arrive soon. Around 22 diaphragm wall panels are made and a guide wall has been completed at May Day Park, while 24 diaphragm wall panels at Shenoy Nagar and 19 others at Washermanpet have been installed. The boring machines will be lowered at these locations when the diaphragm walls are constructed and a pathway tunnel designed to guide the machines to the boring spot is completed. Work to build underground stations is progressing at a brisk pace along Poonamallee High Road for the Central-Tirumangalam underground section and along Anna Salai for Washermanpet to Saidapet underground stretch. Soil investigations are complete and barricades have been set up to identify and move utilities like electrical junction boxes, water supply pipelines and others. Workers started to barricade a median opposite Ripon Building on Sunday while work has begun to construct guide walls near Central railway station. Guide walls have been constructed for more than 100 metres near Kilpauk Medical College. Metro rail has also started shifting electrical junction boxes from Anna Nagar Tower station. In the Washermanpet to Saidapet underground stretch, soil investigations have been completed at Government Estate, LIC and Thousand Lights station locations. Metro rail officials have started identifying utilities at LIC, Thousand lights, Teynampet, Chamiers Road and Saidapet stations to move them before work begins.