Throughout countries in cold climates, the climate results in frost damage to buildings, roads, and railways every winter. Smaller buildings, roads and railways are particularly affected by ground movements due to frost heave. – As the ground freezes, water is drawn from the lower unfrozen soil to the frost front where it freezes forming a series of ice lenses as the frost penetrates the ground. In the change from liquid to solid, water expands 9% in volume.
Based on a Scandinavian idea Rockdelta RB stonewool mats giving you vibration isolation and thermal insulation at the same time.
The ground heaves are a result of ice segregation and ice lenses which form under the following conditions:
- Frost susceptible soils
- Ground water
- Freezing temperatures in the ground
Elimination of any one of these factors will eliminate frost heave for all practical purposes. Therefore, frost heaving can be avoided by removing one of the 3 factors necessary for its foundation. The use of the following will all work as a means to that end; (1) granular backfills; (2) good drainage, and; (3) footings below the depth of frost penetration or insulation for shallow slabs and footings.
However, the most economical method to prevent frost heave is insulation. The insulation retards geothermal heat loss in the earth, thereby reducing the depth of frost penetration. The insulation layer should be buried at a sufficient depth to prevent its damage by the static and dynamic loading, and tp protect it against chemical deterioration under exposure to sunlight and chemical substances.
The ideal insulation material exhibits an approval according to a leading railway specific norm or standard, e.g. DIN 45673 parts 5 or 7, whereby confidence in the structural performance of the material is maximised.
In unheated structures, such as railway trackforms, a continuous insulation mat must be provided beneath the entire area of the structure. The insulation required is reduced if clean, nonfrost susceptible fill is provided beneath the trackform. Even though the nonfrost susceptible fill may freeze, ice lenses will not develop, and consequently, frost heave will be within generally acceptable limits.
Owing to the inorganic and chemically inert nature of stone wool, insulating and resilient Rockdelta mats mean worry-free transportation, storage and installation in any weather. The Rockdelta mats exhibit no transportation hardening, no low-temperature crystallization, no sensitivity to ozone and no sensitivity to sunlight exposure. Picture shown stem from a project in Årstadalen, Sweden. Note the unprotected working area with the frost and snow covered ground.
The purpose of insulating railway infrastructure in areas of seasonal frost is to attenuate frost penetration and thus permit the trackform to exhibit a reduced degree of frost heave.
For satisfactory operation the requirements are that the insulating material must retain a high thermal resistance during the lifetime of the installation despite a varying moisture and chemical regime in the surrounding material. Also, it should not interfere with the stability of the railway structure either because of the plastic nature of the insulation or by creating an unfavourable water condition in the other components of the trackform.
Insulating and resilient Rockdelta mats possess a uniquely high degree of volume compressibility, i.e. they possess a low Poisson’s Ratio. This indicates that the material contains natural voids that readily absorb the compressed material which, in turn, helps to explain why these mats are remarkably ductile, e.g. compared to blocks of polystyrene. As evidenced by the crucial DIN 45673 approvals this has important consequences for the longevity of the mats that boast a fatigue resistance unmatched by any other insulating resilient mat.