Changing hydraulic conductivity in the compression zone of Sta. Maria arch dam foundation. The in situ proof.

The hydro-mechanical coupled behaviour of arch dam foundations is a very complex problem and has so far been given scant attention in literature. The unexpected behaviour of the wide spanned arch dam Sta. Maria triggered numerous in situ investigations and numerical back analyses of the foundation behaviour of the dam, which was believed to be strongly hydro-mechanically coupled. One of these investigations was aimed at measuring the change in hydraulic conductivity of the foundation rock during the cyclic loading of the dam when the reservoir is in operation. The investigation is documented below. The results show clearly that a significant change in conductivity occurs.