The In-situ Properties of the RCC at Lai Chau

摘要

Lai Chau,a 130-m high RCC dam on the Da River in North-West Viet Nam,has been very comprehensively cored.During the first three Stages of coring-there are two further Stages still to come-a fraction under 450 m of core was extracted from the dam body.In all,1 343 samples of core have been tested,307 in compression,340 in direct tension of the parent (unjointed) RCC,677in direct tension of cores containing joints and 164 for modulus in compression and Poisson' s ratio.The paper describes the analysis of all these results and the relationships between the compressive and tensile strengths of manufactured cylinders and the same strengths of cores.All the strengths conformed to the Specified requirements,indeed,apart from the direct tensile strengths of cylinders in the laboratory,they exceeded the requirements by some margin.Further cores are to be extracted from the last two sections of Lai Chau as soon as the RCC has reached a suitable age and access is possible.Such comprehensive testing of the in-situ properties of Lai Chau will enable the Higher Authorities in Vietnam to be confident of the performance of the RCC in the dam body.