Bauer carries out diaphragm wall work for Chennai metro expansion

Like many large cities in India, Chennai has experienced rapid population growth in recent years. The need for infrastructure in this capital of Tamil Nadu state is correspondingly high as a result.

One solution to deal with the high traffic volume in the heavily built-up city is to move it underground. The Chennai Metro was opened in 2015 and so far has two lines with a total length of approximately 46 km. Now the network is to be expanded.

Phase 2 of the extension includes the Chetpet Metro Station, which started in April this year. As part of the project, Bauer Engineering India Pvt Ltd, a subsidiary of Bauer Spezialtiefbau GmbH, was engaged to carry out the required diaphragm wall work.

In total, Bauer constructs more than 15,100 sq m of diaphragm wall up to a depth of 35 m. When building a panel, the work is divided into three steps: excavation of the trench using bentonite as the stabilising slurry, installation of the steel reinforcement cages, and concreting work.

“The steel reinforcement cages are each around 33 m long and weigh 35 t,” said Hassan Farhat, project manager at Bauer India. In total, 286 cu m of concrete is filled in for each diaphragm wall panel in just six hours, with 30 secondary panels produced by the beginning of November.

According to Bauer, what’s special about this project is that there is zero tolerance for the trench excavation. But this is not the only challenge, as the site is in an area with significant rainfall in the monsoon season, i.e. during the construction phase. In addition, the ground composition of sand, silt, stiff clay and rock is very demanding.

“Another challenge is logistics. Since the new metro station is located directly in the urban area, the work needs to be implemented in a very confined space. This requires extreme caution and excellent organisation,” continued Mr Farhat.

A Bauer MC 96 duty-cycle crane with DHG-C hydraulic grab as well as an MC 128 duty-cycle crane with BC 40 cutter are being deployed on the project. Digital tools such as the Bauer data management software b-project and the Virtual Site Installer are also being used. “We are currently running on time and are more than satisfied," said Mr Farhat.

“If everything continues to go as planned, we expect to successfully complete the project before the end of the year, and thus a few weeks before the originally scheduled completion date at the end of January.”

All images: Bauer Group