What is the meaning of frozen soil in the yellow calendar?

Frozen soil means that when the temperature drops below zero degrees Celsius, the water in the soil condenses into ice, freezing the soil together and forming a hard frozen soil layer. In time, frozen soil can be divided into short-term frozen soil, seasonal frozen soil and permafrost. Due to the influence of temperature, when the weather gets warmer, it will freeze and the soil will melt. We call this kind of frozen soil seasonal frozen soil. However, in some places, there is a kind of frozen soil that lasts for many years, and this is permafrost. Such as the Arctic and the Qinghai-Tibet Plateau. The temperature in these places is below zero all the year round, so the frozen soil will not freeze all the year round. Even in hot years, only a small layer of soil on the surface is melted, and the deep layer is still hard frozen soil.

From the distribution range, the permafrost, seasonal permafrost and short-term permafrost account for about 50% of the land area, of which permafrost accounts for 25% of the land area. Because frozen soil is a soil medium which is extremely sensitive to temperature, it contains abundant underground ice. Therefore, frozen soil has rheological properties, and its long-term strength is much lower than its instantaneous strength. It is precisely because of these characteristics that when building engineering buildings in permafrost regions, we must face two major dangers, namely, frost heaving and thawing settlement. With the climate warming, the frozen soil is also deteriorating.

But for frozen soil, if the heat radiated by the soil layer is greater than the heat absorbed every year, the freezing depth will be greater than the melting depth, and the frozen soil will gradually become thicker. This kind of frozen soil is in a relatively stable state and is called developing frozen soil. On the contrary, if the soil absorbs more heat than it emits every year, the ground temperature will increase year by year, and the frozen soil will gradually melt, thin or even disappear, and it will be in an unstable state. We call this frozen soil degenerated permafrost. In addition, there are two kinds of frozen soil, namely, permafrost and non-permafrost. The whole frozen soil means that the frozen soil is distributed horizontally, continuously and without melting zone.

Incomplete frozen soil means that the distribution of frozen soil in horizontal direction is separated, and the melting zone in the middle is separated. Geographically, frozen soil can be divided into two categories: glacial marsh soil and frozen desert soil. Ice marsh soil, also known as tundra soil, is a soil layer with constant moisture. However, the glacial swamp soil has low organic matter content, low cation substitution rate, slightly acidic to acidic reaction and lack of nutrition. Desert permafrost is a layer with dry soil moisture. This kind of frozen soil is characterized by shallow soil layer, more stones and less soil, weak profile development, gravel, polygonal cracks and salt spots on the surface.

This article was originally written by No.1 author and may not be reproduced without authorization.