EVAPORATION MEASUREMENT FOR THE PRESERVATION OF HISTORICAL BUDDHIST MONASTERY AJINA TEPA, TAJIKISTAN

Abstract

One of the destruction mechanisms of historical earthen walls in Ajina Tepa site, Tajikistan is the salt crystallization. Halite, calcite and gypsum are found as the major salts crystallized on the historical walls. Because the rate of crystallization is thought to be a function of evaporation, the evaporation from four earthen walls was measured by using a newly developed portable evaporation meter. Before the measurement, the accuracy of the evaporation meter was carefully studied under the no-wind and the wind conditions in laboratory and field tests in Japan. The effect of average wind velocity on the evaporation measurement was also evaluated before the measurement. It was found that the evaporation rate is big at the foot of the historical wall and is decreasing with height. This feature implies that moisture is mainly supplied from ground and the protection cover of which height is at least 1m is needed to prevent the destruction of historical wall due to the salt crystallization.