Overview on the success story of Ghatghar RCC dams

V.C. Shelke, V.V. Gaikwad and R.S. Gunjal

Roller compacted concrete (RCC) is the key word in dam building industry of today's brave new world. India has also built its first ever RCC dam for the Ghatghar Hydro Electric Project under the Water Resources Department of Government of Maharashtra. The Ghatghar Pumped Storage Scheme comprises of two units of 125 MW each and the use of reversible turbine pumps for two generating units has been done for the first time in India. All three dams had to be built one after another in the increasing order of height and volume of RCC placement. The lessons learned from each earlier dam regarding construction methodology, adequacy of plant and equipment, results of strength obtained proved useful for the next one. This step by step approach has facilitated in increasing the confidence level and the journey towards perfection. Successful completion of three RCC dams in the Ghatghar Project will encourage the adoption of RCC technology in the upcoming new dams in India.

RCC dams at Ghatghar hydro electric project - An overview by the contractor

Sunil D. Sapre and Somshekhar D. Shivagunde

RCC dams - Advantages in economics & construction speed

D.G. Kadkade

The first Roller Compacted Concrete (RCC) dam of the world was Alpe Gera at Sondrio in North Italy. It was executed between 1961 to 1964. The technology at that period was not what it is today. The dam had a total quantity of 1,800,000 m3 concrete. Concrete was fed to the dumpers moving on the dam by use of 6 m3 skips moving on an inclined haulage track as shown in Figure 1. This method of construction was found to be expedient then.

Mix design of RCC for Ghatghar project - An overview

N.B. Ghuge, V.B. Pandhare and C.L. Narkhede

Roller Compacted Concrete has proven to be an economical concrete. Its construction methodology is simple and hence, it has become popular all over the world. About 266 dams have been built using this concrete. Construction period is short providing the structure for early utilisation and thus, saving in cost and time. For the first time in India, it was decided to of construct two storage dams with a saddle dam under the Ghatghar Pumped Storage Scheme in 1994 by Water Resources Department, Government of Maharashtra at the instance of Fly Ash Utilisation Programme (formerly Fly Ash Mission), TIFAC, DST, New Delhi. Many agencies are associated with the guidance, planning, design, research and construction of the dam. MERI, Nashik was entrusted with the mix design of the Roller Compacted Concrete. Since this concrete was new to the Indian scenario, the help of experts (Mr. Ernest K. Schrader of USA and EPDCIL of Japan) in this field was taken to understand and guide the mix design and concrete technology. Trial mixes were carried out and a final mix was finalised. It was tried on test section no. 1 and with modification on test section no. 2. At this juncture RCC consultant Malcolm Dunstan & Associates of UK was invited for guidance. Field specific mix designs were conducted in the field laboratory at project site.

RCC dams: Design considerations for Ghatghar project - A case study

B.B. Gharat and P.B. Phanasgaonkar

Use of Roller Compacted Concrete (RCC) construction technology in gravity dams has increased worldwide. India's first RCC dam project at Ghatghar by the, Water Resource Department, Government of Maharashtra, has proved to be a success of this technology in the country. Two small dams, out of the three, in the Ghatghar project have been completed in 2004 and the main 86 m lower dam has been completed this year. The cost benefit in RCC is achieved due to the speed of construction through the efficient use of machinery and fly ash. The layout and dam design speed up the construction. Simplicity in overall dam layout, galleries, adits, shafts, outlets and spillway have to be planned to avoid stoppage of RCC placement. The galleries in the RCC dams are provided with precast concrete roof without any side or corner reinforcement. The Finite Element Analysis of the dam is necessary to ensure that the stresses around the opening are allowable under the static and earthquake forces. This paper compares the provisions of IS 6512 : 1984 with other international guidelines in light of the learning on Ghatghar project.

Thermal analysis for Ghatghar RCC dam - A case study

S.N. Kulkarni, D.R. Joshi and S.M. Sangale

Ghatghar pumped storage hydroelectric project (2?125 MW) located in Thane and Ahmednagar districts of Maharashtra state consists of Roller Compacted Concrete (RCC) dams for upper and lower reservoirs. It is for the first time in India that RCC technique has been used for construction of gravity dams. The main reason for adopting this technique is its advantage over conventional concrete in speed of construction and its eco-friendly nature since RCC consists of fly ash as its major constituent. As this technique of dam construction has been adopted for the first time in India, extensive basic research was necessary for studying the behaviour of RCC in Indian climate prior to dam design and construction. Accordingly basic research work was done at Central Water and Power Research Station, Pune which is a well known institute of its kind in India. This basic research included various thermal and mechanical properties of RCC. Using the results of the basic study and by conventional analysis methods the safe placement temperature was calculated as 17oC. But, maintaining the placement temperature at 17oC throughout the working season was very difficult as the temperature at site reaches up to 43oC in summer, and moreover it would be very costly to maintain the placement temperature at 17oC. Thus, the transient thermal analysis work carried out for Ghatghar RCC dam helped in increasing the placement temperature by about 5oC which eased the construction and reduced the construction cost as well. This paper briefly describes the thermal analysis carried out for Ghatghar lower dam.

Construction materials for concrete / RCC dams

B.J. Parmar

The bulk of concrete comprises of aggregates, cementing material, admixtures and mixing water. It is therefore necessary to identify various types of aggregates (coarse and fine), the cementing material and chemical admixtures for use in concrete. Mixing water for concrete as required for the concrete also has to be tested before its use in the concrete. Each of the constituents of concrete needs proper investigation before use and its availability from quality and quantity point of view is to be established, so that during the course of construction of the project no difficulty is encountered for achieving the required target of completion. Through laboratory studies the specifications for construction materials have been framed and are being improved considerably with more and more experience to suit the requirement of the construction industry.

Use of fly ash in RCC dams

Anil Bhatnagar and Rajesh Kumar

India as a developing nation is trying to set a strong example of sustainable development amongst its peers. The fly ash utilisation programme was launched with the same objective. Fly ash is used as a pozzolanic substitute for cement in Roller Compacted Concrete dams. Roller Compacted Concrete dam was developed as a result of efforts to design more economical concrete dam that could be constructed rapidly with designed performance. Fly ash in RCC is used not only for saving cement cost, but also for enhancing strength and durability through the use of fly ash as various research work world wide have shown. The use of fly ash which has low specific gravity compared with cement is effective for filling the voids of fine aggregate with small amount of cement. Nearly all RCC dam projects have used fly ash (Siliceous pulverised fly ashes, ASTM class-F) primarily due to spherical particle shape that enhance workability, reduced heat of hydration, less cost, better bond between layers, enhanced durability, etc. As RCC dams are massive and post cooling has not been found to be practical in RCC construction due to continuous placement of RCC, consideration of heat generation is essential and hence the use of fly ash is an apt substitute for cement. The latest trend in RCC dam construction is the adoption of high paste RCC dam with cement and low lime fly ash. Replacement level of fly ash, primarily class F, range from 30-75% of total cementitious material. In NHPC, the first RCC dam was proposed for the Teesta Low dam project Stage-IV at the right bank non overflow part. The percentage of fly ash proposed is 60-65% of total cementitious material.