Superstructure demolition in IndiaPublished 3/7 at 12:22
The Indian demolition company Edifice Engineering located in Durgapur, West Bengal, has carried out one of India’s most spectacular demolition projects. The work involved the demolition of the superstructure of a 12km long bridge, partly on land and partly over the Ganges river.
Edifice Engineering was selected to demolish a superstructure of the 12km bridge with external pre stressing being undertaken during maintenance. The bridge is located in Patna City in the state of Bihar. Patna is located in the very north of India, close to the border of Nepal and only some 350 km from Katmandu. This was for 91 spans with six strands on each wall of the segment having 160t capacity, with each span containing 950 m3 of reinforced concrete. This resulted in 15,000 m2 of diamond cutting and 50,000 m3 of concrete crushing being carried out.
Additionally 20 concrete segments were cut out on each side of the individual pier sections, with the weight of each segment varying between 20t to 65t depending on its location in each span. It was estimated that the total amount of concrete dismantled was 90,000 m3, involving the removal, recovery and recycling of approximately 15,000t of steel.
The project involved 52 land spans being dismantled with a high reach demolition excavators equipped with concrete crushers. The contract value of the demolition of the land spans was some USD $ 5.6M. The demolition of the 39 spans over the river was made by diamond wire cutting, lowered with strand jack systems mounted on girders on the barges below, and then removed to the jetty. Crushing of the sections was undertaken on land. The dismantling and demolition of the river sections had a contract value of €6,9M, with the total contract value of the demolition of all the 91 spans being €11,8M including GST. The project is still on going and the total project time is estimated to be three years.
A variety of equipment is used on the ‘land’ part of the project including a 70t base excavator equipped for demolition with a 26m high reach demolition boom. Attachments used include 4.7t concrete crushers with jaw openings of 1300mm at the tip, as well as two dust suppression systems. A 30t excavator with pulveriser is used for extracting steel rebar from the debris, with a further three machines in use for loading and unloading debris, and two 20t excavators equipped with crusher buckets to downsize debris.
Three tractors and three dumpers are used for the transport of debris and steel. One diamond wire saw is in use for the dismantling of the sections in the spans. A further 1t demolition robot with hydraulic breaker is used for exposing the steel for lap length for the new construction on the old piers. Additionally two mini excavators are used for the same purpose. 15 electrical jackhammers have been used for dressing work of the piers.
Equipment used for the demolition of the spans over the river are three hydraulic concrete wall saws, one high frequency electric wall saw, two wire saws and finally one flat saw. One 30t excavator with pulveriser is used to extract steel from the debris, and one trailer truck for transport of the cut pieces. A core drill system is used to cut the pier hammerhead. Furthermore, and as with the demolition of the land spans, a 1t demolition robot with hydraulic breaker is used for exposing the steel for new construction on the old piers. Additionally two mini excavators are used for the same purpose, with 15 electrical jackhammers having been used for dressing work of the piers.
The job started in July 2017 and will be completed in July 2019.