In this paper, theoretical analysis on flow behavior of snow-water mixtures in pipes was made by using the plug flow model. Bingham flow model was used as the flow model with the plug, and the pressure loss of the flow and the coefficient of the pressure loss were obtained as Eq.(12) and Eq.(23) respectively.
The values calculated from Eq.(23) were compared with the experimental results by Shirakashi et al. And it was found that the values calculated from Eq.(23) are in good agreement with the experimental ones as shown in Fig. 5.
The negative values were obtained in the experiments of the coefficient of the pressure loss by Shirakashi et al. at higher velocities, but the empirical equation (34) obtained by Shirakashi et al. were always positive. Therefore, they modified Eq.(34) and proposed Eq.(35). On the other hand, the model proposed in this paper shows the negative values at higher velocities. So, it was confirmed that the plug flow model proposed in this paper is reasonable.

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This study shows the results of indoor test at low temperature, on the de-icing action and the melting action of sodium chloride (NaCl) and other chemicals used for winter road maintenance. (1)As to the de-icing action, it was tested that the relation between the changes in the composition of phase and the skid resistance on road after applying chemicals.
The solution on the road will not only be effective in lowering the freezing point, but also be helpful in improving skid resistance, as follows,
(1)The skid resistance is already documented to decrease remarkably as soon as the water on the road has frozen. However, the solution on the road does not become slippenly at the freezing point.
(2)Even when the temperature goes down below the freezing point of the solution, increase of the skid resistance is expected more than the case of perfectly icy road surface.
(2)As to the melting action, the relation between the temperature of ice and the amount of melting ice after adding chemicals was tested to clarify the ice-melting effect by chemicals. As the result, it was concluded that ice-melting degree (ice-melting amount, ice-melting velocity) by chemical is liable to be controlled by the up-and-down variation of the tem- perature.

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