Onset of frost
Freezing eruptions are a special type of physical weathering of rocks and other solids . They are caused by frequent alternation of frost and thaw periods .
Emergence
They are particularly common in the winter months in the form of bubble-shaped bulges on road lanes and on asphalt sidewalks and, when their edges collapse, form the familiar potholes .
Solid materials freeze when water can penetrate the interior through a defective surface or lateral cracks. When the water freezes, it increases in volume by about a tenth, which increases the size of these cracks. In the event of repeated thaws and frosts , parts of the material are eventually separated by frost blasting .
In buildings or streets, precipitation or groundwater can also enter from below . B. is derived from an intact road through the frost-protecting gravel in the superstructure or foundation.
consequences
After the surface has begun to break up, the destruction process usually progresses at an accelerated rate because water can now penetrate even more frequently and the mechanical stress on the break edges is added. As a result, a frost breakup expands from a kind of bulge or a wider crevice to a larger hole, as the open edges break away and new cracks open in the material.
A road surface that has been broken up in a circle enlarges and deepens over the course of a few days to weeks, which can ultimately lead to potholes of up to 1 meter in diameter and depths of up to 20 cm. Similar effects can be observed on the corners of walls or on the foundations of fences, where frost chipping off decimeter-sized pieces can occur.
In order to avoid similar effects on small structures such as wayside shrines , cast-in poles or on boundary stones and surveying points , they must be grounded below the frost line , which is an average of 60 cm in Central Europe and more than 1 m in Northern Europe.
Based on the climatic conditions, Germany is divided into three frost zones that have an impact on road construction.
In the ground
A similar type of frost weathering also occurs in natural soil :
- as mechanical- thermal weathering of larger stones up to the smallest stones and sand .
- or as in organic soil frost action (crumbling).
- as the clods of earth disintegrate in the course of winter, which is why the plowing or digging is done in autumn if possible.
- as a slow "freezing up" of stones until they come out of the ground to the surface.
- as the triggering of landslides , when the fissures that are almost always present in natural rock are burst open by ice and the mountainside loses its stability.
- as the shaping of large granite blocks into round pieces, because - analogous to the cracking of a wall corner by frost - the corners of a block are weathered the most.
- In the formation of rubble heaps and so-called frost debris deserts .