The guideway beam on which Mumbai Monorail runs is not as per the standards and specifications thus raising concerns if monorail is safe enough for public. This is what CAG has mentioned in it's latest report.
The guideway beam on which Mumbai Monorail runs is not as per the standards and specifications thus raising concerns if monorail is safe enough for public. This is what CAG has mentioned in it's latest report.
Even to erect the guideway foundation, concrete of lower grade has been used. "The (Larsen & Toubro and Scomi Engineering) LTSE mentioned use of concrete grade M-40 for piles and piles caps in its technical package," mentions the report. By April 2014, a total of 2,580 piles and 637 pile caps had already been constructed using M-35, a lower grade, concrete.
Additionally, the guideway beam has been designed and constructed to take axle load of 11.72 tonnes, despite LTSE in their technical proposal mentioning the design capacity of 12.35 tonnes. "While, the Rolling Stock Car (RSC) actually supplied by LTSE had an axle load of 13.27 tonnes," reads the CAG report. This means the axle load is more by 1.55 tonnes and is causing excessive stress on the structure.
Also, the MMRDA first allowed construction of the guideways and later appointed a consultant to revalidate the design. By the time of appointment of the consultant, the damage had been done with 25% to 97% of the guideway structure under phase I and 11 to 28 per cent under phase II was already completed.
In order to prevent potential damages, the consultant suggested to have a dedicated maintenance plan and periodic inspections of the structure apart from reviewing future design criteria. But the review was not done by the MMRDA.
Additionally, CAG has maintained that durability and stability of the guideways remained a matter of concern because the cycle time for construction on pre-cast pre-stressed guideway frame was reduced from 60 days to 7 days for concreting, curing and first stage stressing of pre-cast beam. Even after these changes, MMRDA didn't assess the long term behaviour of the guideway.
Moreover, the joints of guideway beams are also not as per the standard. The project management consultant had rejected the construction methodology adopted citing that the joints were very stiff thereby reducing the ductility required for seismic zone 4 of Mumbai, still MMRDA did not penalise LTSE and the deviation was termed "as an exception".
The expansion joints of the guideway too has been compromised. As per the contract, these expansion joints' service life was to be 50 years, but the ones installed has a service life of only 20 years. Expansion joints allow thermal expansion due to change in temperature.
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