The Lai Chau HPP is the uppermost hydro power project in the cascade of power plants on the Da River in North West Viet Nam.It includes a 131 m high RCC gravity dam and a 1 200 MW power station.The technical design started in 2010,just after completion of the downstream Son La RCC dam,construction of the Lai Chau RCC dam with 1.884 Mm3 of RCC began in March 2013 and the RCC placement was complete in May 2015.The paper describes the 2D thermal stress analyses carried out during the Technical Design Stage,when only limited data of the RCC properties representing the RCC mix to be used in the dam were available.The methodology of RCC properties estimation and thermal stress models setup is presented to determine the allowable maximum RCC placement temperature to be specified.The paper further describes the 3D thermal stress analyses performed during the Construction Drawings Design Stage,when the RCC mix used for the dam was refined and finally defined and according RCC properties were available,as well as the RCC construction programme finalised.The 3D thermal stress analyses considered a relaxation of the specified RCC placement temperature from 18 to 20 °C and confirmed that a reduction of RCC monoliths joint spacing to 20 m for the largest part of the dam had to be implemented.It was seen in the analyses and through embedded thermistors that one of the most important and effective temperature control measures during the hot seasons,apart from passive and forced cooling,was a rapid RCC placement to reduce ambient heat gains of the fresh RCC.
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