First-of-a-kind for Mumbai: Metro viaduct over water

First-of-a-kind for Mumbai: Metro viaduct over water

The wait to witness a metro viaduct pass over a water body was over with the last span of the 550-m Kasheli Creek metro viaduct in the Mumbai Metropolitan Region (MMR) is erected. This is part of Phase 1 of the Mumbai Metro Line 5, connecting Thane to Kalyan via Bhiwandi. The Kasheli Creek bridge - ...

The wait to witness a metro viaduct pass over a water body was over with the last span of the 550-m Kasheli Creek metro viaduct in the Mumbai Metropolitan Region (MMR) is erected. This is part of Phase 1 of the Mumbai Metro Line 5, connecting Thane to Kalyan via Bhiwandi. The Kasheli Creek bridge - first to be crossing the creek- comprises 13 spans, including nine on water, with each span being 42.23 m in length with 15 segments. What’s more, the spans were erected with the help of launching girders in around four months - precisely 123 days. The bridge has been constructed by Mumbai-based Afcons. Asked how the construction was achieved in just 123 days, Sukesh Singh, Project Manager, Afcons Infrastructure, replies, “The day-to-day activities were monitored at a micro level and exclusive resources were allocated.” The plan Initial establishments like a temporary jetty to facilitate construction inside water were first erected after necessary permissions and approvals. Thereafter, major components such as piling, pile cap, pier, pier cap and segments as superstructure were executed. “The piles were constructed using a reverse circular drilling (RCD) machine,” shares Singh. “A barge of 2,143 mtcapacity and crawler crane of 150 mt along with vibro hammer, diesel generators and tugboat were used.” He adds that the shutter arrangement for the pile cap was built by supporting on a permanent liner of piles. The piers and pier caps were cast by making supporting arrangement on pile caps. The major difference in constructing a metro line over water compared to land isdifferent logistics arrangements.In a marine-based project, all logistics must be done via a temporary jetty whereas on land, all the required material can reach exact span locations. It also requires additional floating devices with provisions to carry heavy equipment like aRCD machine and cranes required for marine construction. “Special safety precautions like life jackets, proper access to floating devices and standby divers are to be ensured,” says Singh.“While executing superstructure erection, such as launching of segments, every single segment was to be fed from the land,i.e. rear feeding by trolley arrangement requiring additional resources and time. In marine construction, meticulous planning and close monitoring are extremely important. The movement of material and resources need to be manoeuvred as per tidal conditions, which needs experienced supervision and required hydrological data. Tech talk Multiple techniques were adopted for construction of the viaduct. In piling, Afcons used the RCD machine that, as Singh says, was mounted on permanent liners, and to carry out the pilling work, a temporary platform on temporary liners was fabricated, assembled and installed. “For the pile cap, pier and pier cap, we capitalised the advantage of an adjacent existing road bridge, with which we transported our material by means of a tyre-mounted hydraulic crane. Even the concreting was carried out by keeping the boom placer on the bridge.” A hanging shutter arrangement was used for casting the tie beams at navigational spans and segment feeding was done with the help of a trolley arrangement from the rear end of launching of segments. Materials used Concrete: 8,893 cu m Reinforcement steel: 1,526 mt HTS: 169 mt Challenges involved Like any other complex project, the construction of Kasheli Creek bridge was challenging. “The rotary drill machine choked frequently due to entanglement of unwanted material,” reveals Singh. “The team was forced by necessity to remove the drilling arrangement completely and reinsert the same after cleaning.” As a major portion of the bridge was over water, the team had to depend on barges and tugboats for construction work. However, tide conditions made the manoeuvre risky and tricky. The marine equipment was moved only during the high tide period. Casting of tie beam in navigational spans became a challenge as it was below the high tide level. There was a tight window of four hours for construction every day. However, owing to meticulous planning and close monitoring of equipment and processes, the team was able to construct 22 tie beams within four months. The use of hanging platform methodology instead of conventional methods saved over 60 per cent of the time required for fixingcollars for the precast pier caps. Measures to ensure onsite worker safety A life jacket was mandatory for each worker. No one was allowed to enter the tugboat without one. All the openings, i.e., access from land to water as well as access on barges, were barricaded. For all shifts, divers were always available onsite. Special safety training and daily toolbox talks were conducted for creating safety awareness. Special mock-up drillswere conducted at the creek location from time to time. Hazard Identification, Risk Assessment and Control (HIRAC) was prepared for works at the creek and compliance of the same was monitored as per requirements. Precautions and more Before starting work in the marine environment, various studies were carried out. This included tidal variation by scalar observation periodically, geotechnical investigation and preparation of a scheme according to available site conditions.Based on the scheme, material, machineries, equipment & resources were identified and mobilised in advance. This bridge is part of Phase1of the Mumbai Metro Line 5. With almost 75 per cent of the project completed, the remaining work is in progress and is expected to be completed by the end of 2023. Project details Project: Metro Line5 Location: Thane to Bhiwandi Construction cost: Rs 8.57 billon Expected completion: End of 2023 Total length: 12.7 km Developer: MMRDA Contractor: Afcons Infrastructure

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