2 名城大学 理工学部環境創造学科（〒468-8502 愛知県名古屋市天白区塩釜口1-501） 土中ガス中の多成分物質移動にDusty Gasモデルが有効であることは，これまでの研究で知られている． しかし，Dusty Gasモデルから分子拡散係数，Knudsen拡散係数，屈曲度と機械的分散係数を求める方法は 確立されていない．そこで，本論文では，2成分のDusty Gasモデルを基にこれらの定数を求める方法を開 発した．その際に，土壌中の2成分の境界で流速と分散係数の変化を考慮できるように，特性曲線型有限 要素法で定式化された移流分散方程式にPowellの共役方向を適用した逆解析プログラムも開発した．本研 究で行った2成分の一次元カラム実験結果に逆解析プログラムを適用して得られた合成分散係数と合成流 速，および今回開発した手法を用いることによりこれらの定数を求めることができることが分かった．

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The aim of this study is to investigate applicability of a numerical simulation method (ASG method) for coupling porous media system (saturation formulas) with an atmosphere (gas) -surface water two phase-flow system to practical problems for overtopping that surface water overflows a bank. In this study we conducted numerical simulations for overtopping a trapezoid bank with permeable surfaces, for overtopping trapezoid bank with a berm and permeable surfaces and for overtopping a trapezoid bank with a berm and impermeable surfaces. Moreover it was assumed that these banks were made of sand (the intrinsic permeability 1.737×10 −11 m 2 ) and the impermeable surface had the intrinsic permeability 1.0×10 −18 m 2 and the thickness of 0.2 m. Consequently, it was found from the results of the numerical simulation with ASG method that there was a zone unsaturated with water (unsaturation zone) in the trapezoid bank with the permeable surfaces and two unsaturation zones in the bank with the berm at the elapsed time 9,000 sec after overtopping. Then the gas pressure in the unsaturation zone rose up to 12 kPa in these cases. Finally in these cases the gas in the unsaturation zone went out the bank. On the other hand the unsturation zone finally remained in two areas beneath the impermeable surfaces of the bank covered with the impermeable material as the results of ASG method. Then the gas pressure also rose up to 8 or 12 kPa in the unsaturation zone. Therefore it was recognized to be able to reproduce the overtopping the banks with various configurations, water contention curves and surfaces and that the gas in the unsaturated zone rose up to 8 -12 kPa, by using ASG method. It is particularly significant that ASG method can represent an interaction between the gas and water in the porous medium and those in surface water considering balance of pressure.