CERI > Cold Region Road Engineering Research Group ( Road Maintenance Research Team ) Japanese

Traffic Engineering Research Team
Snow and Ice Research Team
Scenic Landscape Research Unit
 

 

 

Measures against snow and ice accre-tion on structures


In cold, snowy Hokkaido, snow and ice ac-cretion on bridges and other structures can endanger pedestrians and vehicles. Snow and ice are removed manually, which entails the difficulty of working in high places on bridges and restricting traffic. Other methods of keep-ing these road accessories free of accretion use heating elements to melt snow and ice or coatings to promote sliding. However, the effectiveness of heating systems and coatings varies by weather conditions and by the loca-tion of installation on the structure. The dura-bility of heating systems and coatings needs to be improved. To prevent accreted snow from falling, the Team has been examining lat-tice fences, which take advantage of the vis-coelasticity of snow. The lattice prevents snow from sliding, forming cornices or protruding. Experiments using models show that lattice fences prevent snow from falling and from forming cornices.

 

Experiments using lattice fence models

     
mproving infrastructure in cold, snowy regions involves various climate-related issues. For example, road icing and pavement degradation occur on roads, which are vital to everyday life. The Team performs surveys and researches matters related to road and airport pavements. The aims are to develop measures against road icing and frost heave, to improve the durability of pavements in cold regions, to achieve an eff ective and efficient pavement design method, to realize scientifi; c maintenance of road assets using a pavement management system, and to originate recycling technologies for re-use of industrial wastes in construction. Through this research, the Team is helping to make cold, snowy regions safer and more pleasant.

 

Major research topics

  • Measures against road icing
  • Measures against pavement deterioration in cold, snowy regions
  • Pavement management in cold, snowy regions
  • Method for quality control of recycled pavements in cold, snowy regions

 

 

Study on measures against road icing

 

 

Road icing and measures against it are among the most important issues in cold, snowy regions. Extremely slippery road surfaces became more frequent after studded tires were banned because of environmental concerns, and increases in skid accidents and traffi c congestion have become major issues. Walkways and pe-destrian crossings also become extremely slippery very frequently. The number of pedestrians injured from slipping and fall-ing shows no sign of decline. In Hokkaido, where there is snow cover for almost a quarter of the year, it is important to real-ize "barrier-free" pedestrian mobility by improving the winter walking environ-ment.

 

This research aims to develop pave-ments that mitigate reduction of skid re-sistance when the road surface becomes icy. Pavement materials with anti-freezing eff ects are being developed, and their ef-fectiveness is being verifi; ed. By using a special asphalt mixture that contains chlo-ride or by incising drainage grooves on the pavement surface, anti-freezing pave-ments make snow and ice detach more readily from the road surface, make ice sheets break more easily by the load of running vehicles, and mitigate the re-duction of skid resistance. The Team is examining the durability of anti-freezing pavement materials and anti-freezing performance under various weather con-ditions through indoor tests, test applica-tions on roads in service, and follow-up surveys.

 

The Team is also examining pave-ments with rough surface textures, such as drainage pavements and stone matrix asphalt (SMA) pavements, as measures against road icing. By studying how skid resistance relates to the texture of sur-faces, the Team intends to identify the pavement material with the surface tex-ture that is best at maintaining the skid resistance when there is snow and ice on the surface.

Asphalt pavement incorporating an anti-freeze chemical

 

Asphalt pavement that mitigates freezing through physical action

 

Surface texture of drainage pavement

 

Measuring skid resistance

 

 

Study on improving the durability of pavements in cold regions

 

 

With reduced spending on public works, the efficient construction and maintenance of road pavements has become more important for providing safe, pleasant roads to current road users and those of future generations. The Team performs research to improve the long-term durability of pavements by using new materials and construction methods. With these, the Team proposes methods for reduc-ing the lifecycle costs, which combine costs borne by road administrators and road users.

 

Pavements in Hokkaido are exposed to snowfall and low temperatures, an environ-ment that differs from other parts of Japan. The use of new materials and installation methods in Hokkaido requires knowledge of the effects of heavy snowfall and cold tempera-tures on the durability and effectiveness of the new materials and installation methods, and it requires the determination of the locations that are the most appropriate for such installa-tion.

 

This study aims to develop high-durability pavements, such as polymer modified asphalt and composite pavements; to examine the re-duction of lifecycle costs afforded by the pave-ments; and to establish criteria for application of these materials, such as traffic and weather conditions. The study aims to establish mea-sures against low-temperature cracking of pavements, which is a mode of pavement fail-ure that is often seen in cold regions. For this, the performance of a sheet asphalt installation method is examined.

 

By using polymer modified asphalt, which is more viscous than normal asphalt, pavement rutting was reduced. Indoor tests and surveys of test applications have shown that the dura-bility against rutting for pavements that use polymer modified asphalt is roughly twice that of normal asphalt. By reducing pavement rut-ting, lifecycle costs can be reduced and driving safety under conditions of road icing can be improved.

 

Composite pavements incorporate an as-phalt layer over a concrete layer. They are mainly used in tunnels on high-standard arte-rial roads, where long-term durability is re-quired. Construction costs are higher than for normal concrete pavements, but the durability affords reduced maintenance costs. The pave-ments are smooth to drive on and easy to re-pair, qualities that reduce road user costs and overall costs.

Pavement rutting caused by heavy vehicles

 

 

Facilities and Equipment Falling-Weight

 

 

Deflectometer (FWD)

The falling-weight deflectometer (FWD) accurately mea-sures pavement deflection by applying impact load. The FWD allows ground strength and pavement lifespan to be estimated non-destructively. Determining the internal condi-tion of pavements allows the selection of appropri-ate repair and mainte-nance methods. Yearly inspection allows the estimation of pavement degradation and the es-tablishment of long-term maintenance plans.

 

FWD

 

 

Dynamic Friction Tester (DF tester)

The dynamic friction (DF) tester allows simplified measurement of skid resistance. With this device, the friction coefficient is calculated from resistance measured by pressing a rapidly rotating disk onto the road surface. Attached to the rotating disk are three small pieces of the same rubber that is used for vehicle tires. The device is powered by a car battery and can be carried in a passenger car, and its measurement accuracy is high. It is used in ASTM specification tests.

Dynamic friction tester (bottom view)