Frost line

Among those frost line height or depth position is understood, above which there is frost at a specific weather conditions, that is when (usually at night ) Minimum Temperature is below 0 ° limit.

Freezing level at a higher altitude

The physical reason for the upward relative clearly definable frost line is generally vertical gradients of the air which is an average of 6 ° per kilometer. Has it accordingly, for example, at 1000 m above sea level currently 3 ° C, the 0 ° limit will be about 1500 m altitude. She agrees but only rarely correspond to the snow line. The local conditions are highly dependent on further conditions, which include, inter alia: during the day the prevailing solar radiation, the direction ( exposure) and slope of the mountainside, the local vegetation, the type of soil or bedrock, the wind conditions and much more. And the temperature in the soil is greatly increased, so that a few centimeters, there is a significantly higher temperature at the earth's surface. Conversely, can fail even stronger than in the local agent by night-time image of the frost.

Frost line in the soil

In the depth of the frost line is understood as that depth below the surface, under which it can not give rise to adverse soil temperatures. In the soil and throughout the interior of the earth, the temperature increases downward in mines by an average of 30 degrees per kilometer. Near the surface, the situation is more complicated, because the upper soil layers vary greatly. In any case, it is warmer down because the ground acts as an insulating layer. Only with heavy moisture penetration or solid boulders, this effect is weakened. As a rule, it causes already subside, the seasonal variations of the temperature in a few meters deep.

Nevertheless, it must be expected in our latitudes, that the wintry soil remains warmer than 0 ° C until a depth of around 80 cm. Of course, this depth limit is dependent on the climate, as does about the region of permafrost in Siberia obvious.

Antifreeze in surveying and civil engineering

The frost line is the maximum penetration depth of the frost in the ground. It depends on the climate, the local situation, the water content and soil type. In Central Europe, the frost line is 0.80 to 1.50 m below the surface. The 80 cm depth is observed for all foundations, foundations and measurement pillar to avoid lifting of the concrete due to frost heave. Due to the effect of Auffrierens also gradually stones can come to the surface. Therefore, survey points and important border points must extend in at least this depth.

Under buildings and roads, a gravel layer is poured as an antifreeze in the rule. This makes the rain water is derived and can not cause any more land uplift during freezing. Otherwise, there are tears and frost upheavals.

To supply the construction and agricultural industries with current data, the weather stations measure in addition to the air temperature and that of the soil at different depths.