What is the material used in cave dwellings in northern Shaanxi?

Cave dwelling is a unique living form on the Loess Plateau in northern China, where the ancestors of the Chinese nation lived, multiplied and grew. Cave dwellings are divided into earth caves, stone caves, brick caves, earth bottom caves, Liurafter Liubazi caves and interface caves. Cave dwelling is a product of the Loess Plateau and a symbol of farmers in northern Shaanxi. Ancient yellow land and profound culture have been deposited here, and the people have created cave art (folk art) in northern Shaanxi. In the past, a farmer worked hard all his life, and his basic wish was to build several caves. Marrying a wife in a kiln is a family business. Men dig in the yellow soil, and women do housework and have children in caves. Small caves condense the unique customs of the yellow land. The loess, which is as deep as 100 meters, is extremely difficult to penetrate water and has a strong verticality, which provides a good premise for the development of caves. At the same time, natural conditions such as dry climate, cold winter and less wood also create opportunities for the development and continuation of caves that are warm in winter and cool in summer, very economical and do not need wood. Due to the influence of natural environment, landform and local customs, caves have formed various forms. But judging from the layout and structural form of the building, it can be divided into three forms: leaning on the cliff, sinking and independent. The caves in Yan 'an, northern Shaanxi are mixed with cave-style flat-roofed houses. Cave dwelling is an organic combination of natural landscape and life landscape, which permeates people's love and attachment to the yellow land. The cave is fire-proof and sound-proof, warm in winter and cool in summer, which saves land, labor and economy. It is indeed a perfect architectural form adapted to local conditions. People use the characteristics of loess to build caves, called earth caves, which are usually 7-8 meters deep, more than 3 meters high, about 3 meters wide and up to 20 meters deep. There are two kinds of windows, one is a small square window of about 1 square meter; The other is a round window of about 3-4 square meters. It is characterized by warm winter and cool summer. A stone arch cave with a depth of 7-9 meters and a width of about 3 meters is called a stone cave. Brick kiln has the same style and construction method as the cave, and its appearance is beautiful. Generally, the caves in the First Hospital are all built with 3 or 5 holes. The middle kiln is the main kiln, some are divided into front and rear kilns, and some are 1 in 3 openings. Cave dwellings are generally built in sunny places halfway up the mountain or at the foot of the mountain, and flowers and trees are planted on the brain holes above the cave dwellings. [Edit this paragraph] Cliff cave (Cliff cave) Cliff cave has a back type and a ditch type, and caves are often arranged in curves or broken lines, which has a harmonious and beautiful architectural artistic effect. When the height of the hillside allows, sometimes several terraced caves are arranged, which are similar to buildings. [Edit this paragraph] Sink Cave (underground kiln) Sink Cave is an underground cave, mainly distributed in the loess plateau-an area where there is no slope and ditch wall to use. The practice of this kind of cave dwelling is: first dig a square pit on the spot, and then go to the cave dwelling with four walls to form a quadrangle. On the flat land, people can only see the treetops of the courtyard, but not the houses. [Edit this paragraph] Independent cave (hoop kiln) Independent cave is an arched house covered with soil, including adobe arch cave and brick arch cave. This kind of cave does not need to be close to the mountain and cliff, and it can be independent without losing the advantages of the cave. It can be a single story or a building. If the upper floor is also a hoop kiln, it is called "kiln on kiln"; If the upper floor is a wooden house, it is called a "kiln house". The cave is fire-proof and sound-proof, warm in winter and cool in summer, which saves land, labor and economy. It is indeed a perfect architectural form adapted to local conditions. [Edit this paragraph] What are the construction techniques and structural features of caves in northern Shaanxi? The caves in northern Shaanxi are such arched caves dug according to the mountain situation. Because loess itself has the property of standing upright, the bearing capacity of vault is better than that of flat roof, and vault is generally used in caves to ensure its stability. Northern Shaanxi is characterized by thick soil layer and low groundwater level in the Loess Plateau, and digging caves as dwellings has the advantages of being warm in winter and cool in summer. Cave dwellings can be divided into pit type, cliff type and adobe type. Digging caves on the ground, digging caves on three or four sides to live, with ramps in and out. Cliff caves are caves excavated layer by layer along the mountain side and ditch side. Adobe arch hole is built with adobe arch, covered with soil for thermal insulation. In addition, there are brick cave houses. There are also pit caves in the western Henan plain with thick loess layer, such as the pit caves in Gongxian County, Henan Province. Often the whole village and street are built under terraced fields, and only the crown of the village and the trees on the ground can be seen from a distance. The land on the top of the pit can also grow crops. Longdong also has such underground streets. From the perspective of western environmental architects, this pit building is a perfect civilized building that does not destroy nature. The combination of underground caves still maintains the pattern of traditional quadrangles in the north, with kitchens, warehouses for storing grain, drinking wells and seepage wells, and sheds for raising livestock, forming a comfortable underground courtyard. There are ingenious treatment methods in the utilization of lots, the division of courtyards, the traffic relationship between upper and lower floors, lighting, ventilation and drainage.