ARMA 09-50 Foundation Investigations for Refurbishment Cut-off Walls at Arapuni Dam, New Zealand

摘要

Arapuni Dam, a 64 m high curved concrete gravity structure founded on Quaternary-age ignimbrites, has experienced several seepage flow incidents since its construction between 1925 and 1927. After grouting of the latest flow in 2001, the longer-term future performance of the dam was investigated by triple-tube coring of the foundations, laboratory strength testing, weir and piezometer monitoring of responses to induced changes in pressures in the foundations, and characterization of water chemistry and isotope signatures as well as temperature. The paper describes the use of these techniques to identify four subvertical zones (fissures) controlling the pattern of foundation seepage along joints formed in the Ongatiti Ignimbrite, many of which were either open or infilled with erodible nontronite clay. Recognition of the four fissure zones has enabled the design and construction of four discrete 90 m high cut-off walls through the dam and into its foundations, rather than treatment across the whole dam foundation.