The Commissioner for Metro Rail Safety (CMRS) has issued conditional clearance to Kochi Metro Rail Limited (KMRL) to operate trains through the 1.20-km SN Junction-Thripunithura metro viaduct, provided the metro agency gets the corridor inspected by experts from IIT/CSIR-Structural Engineering Research Centre (SERC) within four months.
In a ‘provisional authorisation’ letter issued on February 22 to KMRL, a copy of which was seen by The Hindu, the CMRS, Anant M. Chowdhary, referred to instances of recording, among others, ‘higher camber values’ in the corridor. He went on to state that the provisional authorisation (to open the corridor for commercial use) would be subject to conditions / stipulations.
His letter says thus: “Based on the records of design camber and actual camber measured for the pre-stressed concrete [PSC] girders, it is found that there are higher camber (up to +575%) recorded compared to the design camber. There were seven design cambers specified, varying from 11 mm to 52 mm, for the similar type of 25-m length PSC girder. During statutory inspection, this issue was highlighted for which no satisfactory details were furnished. Subsequently, KMRL has come up with revised design camber values. Measured camber values were still found higher (up to +263%) compared to revised design camber values.”
Four-month validity
The letter said that the complete exercise of reassessing the design camber, only after the issue was flagged by the CMRS, lowered the confidence in the entire process of designing and record keeping. “This scenario is not acceptable. In this background, provisional authorisation is being issued with a validity of four months. During this time, KMRL must get the technical assessment of design, safety impact of ‘excess camber in the PSC girders’, and recommendations on improving quality control by reputed institutes like IITs/CSIR-SERC Chennai. On submission of the findings and recommendations of the institute by KMRL, a decision on regular authorisation shall be taken by the CMRS,” it added.
Open web girder
The letter also points to, among others, the difference in level between the left hand and right hand sides of the girder in lateral direction in the open web girder (OWG) that was built off Thripunthura S.N. Junction. It thus directed KMRL to keep the OWG under observation for four months from the date of commissioning of the corridor and to submit a special report. It further directed the metro agency to approach the CMRS after complying with the stipulations within four months to seek regular authorisation. Based on his inspection of the corridor on February 12 and 13 and speed test by a special train, the CMRS has provisionally authorised the opening of the section for use, up to a maximum permissible speed of 60 kmph.
Meanwhile, KMRL sources said the issue of ‘provisional authorisation’ letter was not uncommon in metro rail systems. “We would rope in experts from reputed institutions like IITs / CSIR-SERC Chennai to do the necessary technical assessments, following which a compliance report would be handed over to the CMRS within the four-month time frame,” they said.
This would not delay the commencement of commercial operations in the corridor. The Thripunithura terminal station is being tidied, and the date of commercial operations would be announced shortly,
