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Last update 30/05/2007

Task 2_3:- “Managing spring thaw weakening”

Lead Contact

Timo Saarenketo and Saara Aho, Roadscanners Oy

Objective

The report summarizes the work done on Task 2_3 “Spring Thaw Weakening” of the Roadex II project. The report will describe the theory behind spring thaw weakening and different load restriction policies used in the cold climate areas. It will also report the results of the field tests done in Scotland, Sweden and Norway and present some new structural solutions which have been found to work well at spring thaw weakening sites. Finally, new technologies for both road owners and/or road users that could be used in more effective spring thaw weakening management will be revealed.

Outputs

The goal for subproject 2_3 “Spring Thaw Weakening” was to collect information regarding one of the most difficult challenges in low volume road condition management in cold climate areas, managing road condition during the spring thaw weakening period. This has to be done in a way that minimizes the impact of transportation problems on local livelihoods without destroying road structures or reducing the service level of the road for the rest of the year. The survey has followed the Roadex II Project phase II theme of “understanding and analysis” by using new technologies to monitor spring thaw problems and then analysing the problem sections so as to better understand the processes behind the problems.

The report has six major parts.

The first part of the report presents the theory behind spring thaw weakening, the scope and the scale of spring thaw problems as well as the different load restriction policies used in the cold climate areas. The second part of the report summarizes the key results from the extensive field testing done at the Roadex test sites. The third part of this report presents a new classification for spring thaw weakening phases that can be used in monitoring and communication terminology when describing the status of spring thaw but is should also be used in the decision making process involved when deciding whether to remove or implement load restrictions. In the fourth part a new classification for spring thaw weakening sites is presented. This classification is important in order to be able to select an optimum strengthening method for each type of spring thaw problem. These strengthening techniques and structures and their life cycle costs are presented in the fifth part of this work. The sixth part presents new technologies and ideas for better spring thaw weakening management on low volume roads.

The Roadex II survey results regarding seasonal changes and spring thaw weakening produced valuable information regarding the processes behind road damage and the complexity of these processes. Test results indicated that standard truckloads can easily break the road during the weakest phases in spring incurring major costs to road owners as well as an unpleasant ride for other road users during the rest of the year. On the other hand it can be estimated that in Finland and in Sweden, for instance, every day of load restrictions results in more than one million euro extra cost for the forest industry. The results also reveal that the critical weakening phase is often quite short and that is why good monitoring systems with better spring thaw weakening models will generate major savings for the haulage companies using low volume roads. Other promising solutions that should be studied further are the idea of recovery times after a truck pass and the use of CTI (central tyre inflation) techniques or special axle configurations to reduce the risk of damaging roads during the spring thaw. However the long term goal should be to repair and strengthen all of the weak road sections, and only the weak sections, so that load restrictions would no longer be needed.

Links

Roadscanners Oy

Acknowledgments

The authors would like to express their gratitude to Ron Munro and Frank MacCulloch from Scotland, Johan Ullberg from Sweden as well as Seppo Kosonen, Tapani Pöyry, Timo Hyvönen, Tarmo Posti and Kari Parikka from Finland for helping with the field test arrangements. Special thanks to Nuutti Vuorimies from Finland for providing survey data for this research and also to Pauli Kolisoja from Finland, Svante Johansson from Sweden and Geir Berntsen from Norway for their valuable help in this survey.

Virpi Halttu has edited the report, Kent Middleton has checked the language and Jaakko Saarenketo has given valuable help with graphics and data analysis, all of the aforementioned people are from Roadscanners. In addition, all of the Roadscanners crew and many others have given help with data collection and analysis.

Finally the authors would like to acknowledge the Roadex II Steering Committee and the Road Condition Working Team for its encouragement and valuable guidance in this work.