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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.

Unsaturated hydraulic property (relation between the water retention curve and hydraulic conductivity function) of soft rock must be properly estimated for analyzing the saturated-unsaturated groundwater flow such as the flow around a tunnel, rock surface and so forth. In this study a practical technique for estimating the unsaturated hydraulic property of soft rock was developed on the basis of the Campbell model and Genetic Algorithm (GA). The major objectives of the present study are the following two; 1) investigation whether or not the Campbell model can be applied to soft rock for approximating the unsaturated hydraulic properties and 2) application of GA technique for estimating two parameters included in the Campbell model. These parameters were estimated through the inverse analysis of the transient change of evaporation rates from a surface of disk shaped specimen of Tertiary sedimentary rock which are sampled from the Rokkasho area, Aomori prefecture. Two transient evaporation experiments under different atmospheric conditions were proposed for the estimation. The Campbell's parameters of 13 soft rock specimens (5 sandstone and 8 tuff breccia specimens) were estimated through those types of experiments. As the results it was clearly found that the transient change of evaporation rates can be well fitted by the Campbell model except for the region of low saturation and this fact implies that the Campbell model can be applied to the soft rock. And also it was found that, the GA is a promising technique for parameters estimation in the inverse solution method. It can be concluded that the techniques are practically for estimating the unsaturated hydraulic properties of soft rock.

博士の専攻分野の名称 : 博士(学術)学位授与年月日 : 平成20年3月24日