Kiyoshi Takeichi

Ice Formation and the Effectiveness of Deicing Agent on Porous Asphalt and Stone Mastic Asphalt

Porous asphalt (PA) and stone mastic asphalt (SMA) are widely used by many transportation agencies and public works officials. However, the best winter maintenance practices for PA and SMA are unclear and generally unquantified. In this study, laboratory tests under controlled, artificial wintry conditions were conducted to evaluate the winter performance of PA and SMA. The test results are summarized as follows: (a) PA was effective at reducing the amount of water that formed an ice layer on the pavement surface and the thickness of the ice layer. SMA had intermediate effects between those of dense-graded asphalt (DGA) and PA. (b) The rate of decrease in ice layer thickness was found to be the largest for PA; that for SMA was intermediate between those for DGA and PA. (c) The features described above were dependent on the temperature and the amount of water applied. Analysis of the experimental data found that the coefficient of friction had a strong correlation with ice layer thickness, and the ice layer thickness was predicted from mean profile depth, permeability, temperature, water dosage, deicer application amount, and number of wheel passes. Accordingly, the study suggests the possibility of determining the ice layer thickness at which friction-generating contact between the pavement and the tire is reduced and how much deicer is needed to maintain a certain level of service based on pavement type, weather conditions, and traffic volume.

Performance of various antifreezing pavements by field test

Eleven kinds of antifreezing pavement that rely on physical action were tested. The test pavements were compared with conventional pavements. The pavements covered with elastic materials or elastic material mixed with conventional material, both of which rely on surface deflection by the load of passing vehicles to break ice, were found to be more effective than the pavements with a coarse surface. A pavement into which grooves are cut and filled with urethane resin (Test Pavement B3) and a pavement with cylindrical or doughnut-shaped rubber embedded at regular intervals in the surface (Test Pavement B4) had high anti-freezing effectiveness. Based on these results, a model intersection was installed with these two pavement types of high antifreezing effectiveness. A survey of pedestrians at the intersection was conducted. Of the respondents, 45 percent answered that it was easier to walk on these kinds of pavements than on conventional pavement. There was less delay in the starting of automobiles when the traffic light turned green with B3 pavement than with other types of pavement. These results confirm that application of antifreezing pavement is effective for pedestrians and automobiles. Further study should focus on confirming the long-term durability and performance life.

A METHOD FOR ESTMATING FRICTION COEFFICIENTS OF ASPHALT AND ROUGH TEXTURED PAVEMENT SURFACES WITH ICE FILM SUBJECTED TO MELTING BY DEICING AGENTS

The thickness of ice film and the road surface friction coefficient (μ) on dense-graded, porous and stone mastic asphalt pavement surfaces after the spreading of deicing agents were evaluated from indoor experiments. Based on the experimental results, a method for estimating μ on these pavement surfaces after deicing-agent application was proposed in this paper. Moreover, the changes in μ with temperature after deicing-agent application were compared between pavements from results simulated using the proposed method. The results were as follows. (1) The mean thickness of ice film on these pavement surfaces after water decreased linearly with increase in the amount of deicing agent spread. (2) μ decreases exponentially with increase in the mean thickness of ice film. (3) The ratios of the amount of deicing agents not acting on the melting ice to the amount of deicing agents sprayed tend to decrease with increase in the amount of water applied in the case of the porous and stone mastic asphalt pavements. It was shown that the value of μ after deicing agents were spread differs depending on pavement type, even though the road surface temperatures, the amounts of water and deicing agents applied were all the same. 本論文では，密粒度舗装，機能性SMAおよび排水性舗装を対象に，低温恒温室で氷膜路面への凍結防止剤散布実験を実施し，凍結防止剤散布後の各舗装上の氷膜厚および路面すべり摩擦係数μを評価した．また，凍結防止剤散布後のμの推定法を構築し，任意の路面温度における凍結防止剤散布後のμの推定値を舗装種別間で比較した． 結果，(1)平均氷膜厚は，いずれの舗装も凍結防止剤散布量の増大とともに線形的に低下する．(2)μは，平均氷膜厚の増大とともに指数関数的に低下する．(3)機能性SMAおよび排水性舗装の鉛直損失塩率は，散水量の増大につれて減少する傾向にある，ことが分かった．本研究により，凍結防止剤散布後のμは，路面温度・散水量・凍結防止剤散布量が同じであっても，舗装の種類によって異なることが示された．

TRANSFERRING PHENOMENA OF SALT AND MELTING WATER AFTER SALT APPLICATION ON ROUGH TEXTURED PAVEMENTS

Rough textured pavements are expected to result in different pavement conditions from dense graded pavements after salt application, due to having a rough texture / drainage function. Therefore, application methods according to the types of pavements are required to establish. Authors have quantified transferring phenomena of salt and melting water after salt application both on rough textured pavements and dense graded pavement, using the full-scale trucking test equipment. Besides, the authors conducted multiple regression analysis to clarify contribution factors that affect road surface conditions. 凍結防止剤散布による冬期路面管理は，費用対効果や塩害抑制の点から合理的な散布方法が求められている．凍結路面の補助的対策工として排水性舗装や機能性SMAなどの粗面系舗装が施工されているが，粗面系舗装は粗な路面テクスチャや排水機能を有するため，凍結防止剤散布後の路面状態の変化は密粒度舗装と異なると予想されるが，定量的な検証が不十分である．本研究では，粗面系舗装と密粒度舗装上に散水して凍結路面を作製し，凍結防止剤散布後に一定数の車輪走行があった場合の，凍結防止剤および融解水の貯留と流出などの移動現象を，室内実験を行って定量的に示した．さらに，重回帰分析を行い，路面状態の変化に寄与する要因の分析を行った．

STUDY ON DISCRIMINATION OF WINTER PAVEMENT CONDITIONS BY WAVELET ANALYSIS

As for the discrimination of winter pavement conditions by image processing, the previous study was focused on the analysis based on the fundamental statistical parameter and Fourier transform. This paper is to study the discriminant methods by one and two dimensional wavelet analyses, which enable space-spatial frequency analysis, from the view point of control of the location and localized existence of various winter pavement conditions.