Single pile could reduce land needed and speed up work compared to multiple piles

The project cost and the quantum of land needed for Kochi Metro Rail will come down if the trial run on the monopile technique succeeds. This will also lessen traffic disruption during the metro rail construction and speed up works when compared with pillars built over multiple pile groups. The multiple piles have three or four piles, each pile having a diameter of 1 metre. The monopile trial began near the KSRTC’s main bus stand here on Friday. “This will go on for two or three days and a report will be ready in a fortnight,” said a DMRC official.

In this, a 1,275-tonne vertical test load and 60-tonne lateral load will be loaded incrementally on a monopile having a two-metre diameter. “An instrumentation team will monitor the trial using strain gauges embedded in the pile. The incremental loading will be carried out for around two days and this will be 1.5 times the designed load. This 50 per cent extra load has been factored in as a safety measure. We also did a modern integrity test using cross-hole sonic method,” said an engineer at the site.

The strain gauges are linked to computers by wires. The pressure gauge will display the pressure applied on the pile. Sree Giri Consultants, with Prof P K Aravindan as principal consultant, is the design consultant for piling. He was former professor in structural engineering at the Chennai IIT.

If found successful, the metro’s via duct will be built over monopiles. It will reduce the space that needs to be barricaded on the road for construction.

The area near the KSRTC bus stand was chosen since it is among the slushiest areas in the city. “If successful, the technique can be safely adopted for the metro which passes through harder terrain.” Though monopiling will require heavy capacity hydraulic rigs, the construction time will be reduced.

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