Frost control — Design, construction and monitoring of TPPT test roads

The Road Structures Research Programme (TPPT) is a nine-year (1993–2001) research programme of the Finnish National Road Administration (FinnRA). The specific objective of the program is to reduce the annual costs of new roads with 10% and of the existing roads with 5%. The major environmental aspect is the use of local secondary materials with the aim of protecting natural gravel deposits.The primary mean to carry out the tasks of the program is field testing of new materials and structural solutions. The field test program is supported with laboratory testing of the layer materials. In TPPT the development of the new structures has been divided to three categories, where the main criteria are fatique, frost action and geotechnical bearing capasity; i.e. subgrade deformations and settlements. In TPPT program will be constructed 10–15 frost test roads. In each test road there will be 3–10 test sections. Frost protection structures, reinforced structures, moraine structures and integrated structures were designed. Three frost protection structures have been constructed in 1995, two in Lapland and one in Oulu district of FinnRA. Soil and frost conditions were different in these test roads. The freezing of frost-susceptible subgrade was structurally limited by using a frost-protective structure consisting of sod peat. The thickness of the peat layer varied from 30 cm to 60 cm. Test structures are compared with the reference solutions of a thin asphalt course and thick unbound base/subbase courses. Test structures were instrumented and the behaviour has been monitored since they were finished in the autumn 1995. The behaviour of test structures were monitored during the winter 1995–96 by measuring frost penetration, frost heave, soil temperature at various depths, groundwater table, snow depth beside the road and variation of moisture content and thermal conductivity of the peat. Results and measurements will be analysed. During 1996 will be constructed moraine and reinforced structures. In Lapland moraine structures will be drained. In reinforced structures steel sheet profiles and steel meshes will be used with crashed rock and blast furnace slag.