The basic principle of conservation of cultural heritage had been considered to keep the original structure with the original material. Authenticity is referred to the quality of being the truth of the heritage. The authenticity has been discussed only for the upper part of heritage structures, and the foundation of the structure was neglected. However, the foundation is one of components of the heritage structure and ICOMOS established the concept of the authenticity of foundation in 2010. The restoration work for Pisa Tower started in 1990 and completed in 2001 without any discussion of the authenticity of the foundation. However, the authenticity of the foundation was completely reserved. Main tower of Bayon temple, Angkor Thom, Cambodia was found to have been standing by direct foundation on a sand filled mound with thickness in 15m for more than 700years under monsoon climate condition. The sand used for construction of the mound was found to have very high strength at low water content due to negative high water suction pressure. The high strength of the sand and a unique rain type of "squall" made it possible for the shallow foundation on the thick sand mound to withstand the rainy climate. This paper describes several cases of the authenticity of foundation and shows the finding process of the special characteristics of "Angkor Sand".
Yoshinori Iwasaki (Thu,) studied this question.