Construction Pioneering on Frozen Dirt Rigid foam insulation- This is rudimentary. A layer of rigid foam insulation is placed over the "original ground" A.K.A. permafrost. The fill that comprises the road embankment is placed over the insulation. The finished road has a layer of insulation burried in its heart. The physical concept is straightforward- the insulation forms a thermal barrier that seperates the heated road surface from the frozen subsoil. Although this method is usualy not economicaly effective on its own, rigid insulation is almost always used as a component in other advanced permafrost engineering systems. Wood Chips- Believe it or not, a road section just South of Fairbanks was built with a core made of woodchip fill. As with the rigid insulation, the wood chips were intended to serve as a thermal barrier, thus keeping the subsoil cold and stable. Incidental to the low thermal conductivity, the wood chip fill is lightweight. Consequently, if thawing were to occur there would be a much smaller weight force imposed on the ground by the road, and therefore less settlement. Unfortunately the wood chips did not provide sufficient support for the vehicle loads- excessive wheel ruts developed in the pavement. Although this method was not immediately successful, it demonstrates the spirit of exploration that is crucial if problems such as this are going to be solved. Paint it White-In several places in Alaska, roads have been painted white. I think it is common knowledge that dark colored things absorb more heat that light colored things. Try this easy experiment. On a hot summer day in Fairbanks, place one hand on the blacktop and one hand on the (white) concrete sidewalk. The road will be substantialy hotter. This is a physical concept that goes by the name of Albedo.Albedo refers to a materials ability to reflect or absorb energy as a function of its' color. It makes sense then that a white road would deliver far less heat to the frozen ground beneath than would a normal black asphalt road. My research indicates that this method is not being actively persued at the present time. I suspect that this is because the paint is expensive and not extremely durable. This method makes scientific sense but simply is not economicaly feasible. Peat-I find this method particularly interesting. It is similar to the rigid foam insulation scheme, except that a several foot layer of peat is used as a thermal barrier. When peat is frozen it is a poor insulator, but when it is thawed it is an effective thermal barrier. During the winter months, the subsoil has unfettered thermal contact with the frigid ambient air and is cooled drasticly. In the summer the peat thaws and becomes a heat block that protects the fragile permafrost foundation. In this way the peat is a one way "heat switch" that allows heat to escape in the winter and prevents heat from entering in the summer months. This method did not return the desired success and is not currently being used in Alaska. GeoTextile Geotextile fabric is a grid type mesh that is placed in layers within the soil of a road embankment. It strengthens the mass of soil by making it a homogenous mass. It can be likened to reinforcing steel found in concrete structures or fiberglass strands found in fiberglass. Geotextiles have been used in road embankments over permafrost in an effort to stop the rotating failure associated with thaw settlement (by increasing the shear strength of the soil mass). Geotextile on its' own has not been shown to be an effective way to build on permafrost. Pre-Thawing Roads on permafrost fail because the ground directly beneath the road settles excessively. Consequently most techniques explored here are based on preventing thaw, and settlement from occuring. Another approach is to thaw the ground prior to building on it. This can be done easily by clearing the vegetation from the building site and allowing the ground to thaw naturaly over several years. This method is used rarely if ever because most construction schedules do not allow the luxury of time. Also, thawed permafrost often leaves a super saturated silt that is subject to moisture consolidation- a problem of its own. Still, pre-thawing is a method of dealing with permafrost that may be feasible in certain unique situations.