Record Concreting of over 6,50,000 m3 by Patel Engineering Ltd.

    Patel Engineering Ltd
    A record concreting of over 6,50,000 m3 in 12 months was achieved by Patel Engineering Ltd at Ghatghar Roller Compacted Concrete Dam project.

    Two Schwing Stetter Concrete Batching and Mixing plants–Models HN 3.0 (120 m3/hr) and one HN 4.0 (160 m3/hr) were installed aggregating to 400 m3/hr batching capacity. The plants had twin shaft mixers and the control system was Stetter MCI 300 system.

    Ghatghar Pumped Storage Scheme is a hydropower generation project constructed by Irrigation Department Govt. of Maharashtra. Total 250 MW power will be produced from this hydro power plant. Three dams Saddle Dam No. 1, 2, and Upper Dam, build up the upper reservoir. Lower dam builds up the lower reservoir. Water conductor system consists of inclined underground pressure shaft and the underground powerhouse, which has two units of 125 MW turbines. These turbines act as reversible pumps. In nonpeak hours the water from the Lower Dam reservoir, which will be filled with water, and stored after power generation, will be pumped back to Upper Reservoir. Saddle Dam No. 1, Upper Dam and Lower Dam are built in Roller Compacted Concrete.

    Principal designers of the project are EPDC, Japan, in association with Tata Consulting Engineers, India and Malcolm Dunstan and Associates (MD&A) U.K.

    The project was awarded in November 2001 to Patel Engineering, Mumbai, India’s one of the oldest and experienced general contractors. ASI RCC (ASI) of Buena Vista, Colorado, USA, a well-established international contractor is a wholly owned subsidiary of Patel Engineering and they provided technical expertise for the construction of the RCC Dams.

    RCC Work

    Different methods of delivery of RCC into the dam body were studied and finally best option was selected and the entire site layout was finalized. As per the layout all the equipment were erected. It was decided to place RCC in two halves so as to avoid un-planned cold joints.

    The RCC delivery system comprised of belt conveyor delivering 400 m3 /hr. Four waterchilling plants were installed for chilled water supply to three batching plants and ice plants. Two crushing and screening plants for aggregates production were installed. One 250 TPH crushing plant and 100 TPH were deployed. Two 120 TPH and one 150 TPH ice flake plant were commissioned, having automatic ice handling system. Equipment for RCC placement on dam body comprised of 20-ton dump trucks for collecting RCC from Belt conveyor and truck unloader, D-5 dozer for spreading RCC, 10-ton vibratory roller for compaction. Cranes for form erection and many other minor equipment like high frequency vibrators, small roller etc.

    RCC Placement

    Patel Engineering Ltd
    The RCC placement was planned to complete in 16 working months excluding one monsoon of four months. Total 250,000 cu.m of RCC was placed in the first season. Balance 45,000 cu m was to be placed in the next season. Total of more than 6,00,000 cu m. or concrete was placed in 12 working months.

    RCC Cooling

    The temperature of RCC had to be maintained at the placement point between 17-22o C. Accordingly the RCC cooling system was designed. Maintaining temperature in this bracket required pre-chilling of aggregates, use of chilled water and flake ice. Hence, wet belt conveyor system designed by IIT, Bombay for chilling aggregates from temperature as high as 43 oC was used. This required 1200 TR integrated water-chilling plant and other sub-systems like water filtration plant, water recirculation pump, pipeline network and so on. Flake ice was used as partial replacement to add water to the RCC mix in the mixer. Three dedicated Ice plants to deliver flake ice to three batching plants were commissioned. Two flake ice plants were of 120 TPH and one was of 150 TPH capacity.

    Schwing Stetter

    A complete operation and maintenance contract was handled by Schwing Stetter team to ensure high availability of the plant. The 3 plants delivered on availability factor of close to 97%. “When reliability and optimum performance were required, we only trusted Schwing Stetter to deliver,” said Mr. Rupen Patel (Managing Director) Patel Engineering

    Major Highlights

    Total Concrete Quantity in 12 Months:- 6,10,903 m3 (Dec 04-Apr 06) (June to Oct 06-no work). Average of 50,908 m3 per month.

    Concrete Pumping record for the Tunnel Shaft Vertical Pumping

    With a Schwing BP 250 HDE Concrete Pump, Concrete M/s R.Shah & Co. pumped M25 grade concrete through a distance of 30 mtr. horizontal and 67 mtr. vertical.

    Down Pumping

    With the same SCHWING BP 25 E at R J Shah & Co. The BP250 was used to pump M25 grade concrete down through 88 mtr. Pipeline which included 04 nos.90 degree bends and 07 nos. S bends. The Level Difference between pump and point 72 mtrs. (Down) For West Shotcreting Top Shot Mobile TSM 30.10 was used extensively for shotcreting of the tunnels. Speaking, about the project, Mr. B. K.Chakraborty Sr. V. P. Plant, Patel Engineering said "The project was well executed and the availability of the plants was well at par with international standards."

    NBMCW May 2007

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