What is the freezing depth of the soil and what does the maximum frozen depth mean

Chinese permafrost can be divided into seasonal permafrost and permafrost. Seasonal permafrost accounts for more than half of China's territory, and its southern boundary extends from Zhangfeng in Yunnan Province in the west, through Kunming and Guiyang in the east, around the northern edge of the Sichuan Basin, to Changsha, Anqing and Hangzhou. The seasonal freezing depth can exceed 3 m in the southern part of Heilongjiang Province, the northeastern part of Inner Mongolia and the northwest part of Jilin Province, and decreases with the decrease of latitude in the south.

The permafrost is distributed in the Great and Small Khing'an Mountains in the northeast, the Altai Mountains, the Tianshan Mountains, the Qilian Mountains and the Qinghai-Tibet Plateau in the west, with a total area of 1 5 percent of the national territory. It has been proposed that China's permafrost is divided into permafrost (more than 2 years), seasonal permafrost (more than 1 month), and transient permafrost (less than 1 month), and the premise of its zoning is that the annual average ground temperature, the lowest monthly average ground temperature, and the extreme minimum ground temperature are equal to or lower than 0. The southern boundary of the instantaneous permafrost roughly coincides with the Tropic of Capricorn.

The main characteristics of permafrost are as follows.

Distribution The permafrost in China can be divided into high-latitude permafrost and high-altitude permafrost, the former is distributed in the northeast region, and the latter is distributed in the western alpine plateau and some higher mountains in the east (such as Huanggangliang Mountain, Changbai Mountain, Wutai Mountain, Taibai Mountain at the southern end of the Daxing'an Mountains).

Refers to the thickness of the permafrost.

Appendix F of the Technical Code for Building Foundation Treatment (JGJ79-2002) can be consulted.

Entering the Arctic Circle, the thickness of permafrost can reach 200,600 meters, and in some places even 1,000 meters. On the shores of the Arctic Ocean, the frozen ridge is 400,900 metres thick, making it the last place in the world to have the thickest permafrost, with the thickest place at 1,400 metres.

China's permafrost covers an area of about 10,000 square kilometers, mainly concentrated in the Qinghai-Tibet Plateau and the small Xing'an Mountains. For example, Erenhot in Inner Mongolia and Wucha in Xinjiang are both above 300 centimeters, and the Bayinbrook Meteorological Tremor Station in Hejing County, located in the hinterland of the Tianshan Mountains in Xinjiang, has recorded a depth of 439 centimeters, which is the champion in China's permafrost records.

The maximum of the maximum permafrost depth values in the calendar year.

According to the duration of freezing, it can be divided into:

1. Temporary frozen soil, that is, the soil or loose rock layer that is temporarily frozen and melted soon due to weather changes.

2. Seasonal frozen soil refers to the soil or loose rock layer that freezes in winter and thaws in spring. The depth of the permafrost is determined by factors such as natural geographical conditions and the physical properties of the soil.

3. Permafrost, also known as "permafrost", refers to soil and loose rocks that have been frozen continuously for many years. According to the spatial distribution, it can be divided into continuous permafrost and discontinuous permafrost. For example, the permafrost in Siberia is connected in large areas, while the permafrost in Europe is distributed in blocks.

The place between the massive permafrost that is not permanently frozen is called a "thaw island".

It is the maximum thickness of frozen soil in winter, which refers to the ground.

The tundra, also known as tundra or tundra, is derived from the Sámi word tūndra (genitive of tundar), which means "plain without trees". In physical geography, it refers to the environment where trees cannot grow due to low temperatures and short growing seasons; In geology refers to a variety of rocks and soils below zero degrees Celsius and containing ice. Generally, it can be divided into short-term permafrost (hours, days and half a month), seasonal permafrost (half a month to several months) and permafrost (also known as permafrost, which refers to a layer of frozen soil that lasts for two years or more).

Permafrost, seasonal and permafrost areas on Earth cover about 50 per cent of the land area, of which permafrost covers 25 per cent of the land area.

Permafrost is an extremely temperature-sensitive soil medium that is rich in subsurface ice. As a result, permafrost is rheological and its long-term strength is much lower than the instantaneous strength characteristic. Because of these characteristics, the construction of engineering structures in permafrost areas must face two major dangers:

Frost heave and thaw sink. China's Qinghai-Tibet Railway has a section of the railway that needs to pass through permafrost. Engineers need to stabilize the temperature of the permafrost through a variety of methods to avoid uneven railway subgrade due to the transformation of permafrost and prevent accidents.

Nearly half of the territory of the former Soviet Union and Canada is permafrost, 85% of Alaska is permafrost, and permafrost has been found at the summit of Mount Kilimanjaro near the equator.