Contenido

La tierra suele requerir algún tipo de procesamiento para su uso en la construcción. Puede combinarse con agua para hacer barro, puede añadirse paja, puede utilizarse algún tipo de material estabilizador como cal o cemento para endurecer la tierra y puede compactarse para aumentar su resistencia.[9]​.

Mud

Adobe construction is one of the oldest methods of building walls. Wet clay is shaped by hand to form the base of a wall and left to dry. More mud is added and left to dry to form successive courses until the wall is completed. In the case of soaked mud, a handmade mold is filled with wetter clay and allowed to dry.[10]​ In Iran, soaked mud walls are called chine construction. Each course has a thickness of 460 to 610 mm and a height of 460 to 610 mm. This technique is often used in garden walls, but not in house construction, presumably because of concerns about the strength of walls constructed in this way.[11]​ A disadvantage of this method is that a lot of time can be wasted waiting for each course to dry.[12]​ Another technique, used in areas where wood is abundant, is to build a wood-frame house and fill it with mud, mainly to insulate it. In some areas of England a similar technique was used with cob.[10]​.

cob

Adobe, sometimes called "monolithic adobe",[13]​ is a natural building material made of earth that includes clay, sand or small stones, and an organic material such as straw. Adobe walls are usually built in courses, have no mortar joints, and require 30% or more clay in the soil. It can be used as fill in post-and-beam buildings, but is often used for load-bearing walls and can support up to two stories. A cob wall must have a minimum thickness of 410 mm and the ratio between width and height must not exceed one in ten.[13]​ It is normally plastered inside and out with a mixture of lime, earth and sand. Cob is fireproof and its thermal mass helps stabilize interior temperatures.[13] Tests have shown that cob has some resistance to seismic activity. However, building codes in developed countries may not recognize cob as an approved material.[14]​.

sod or clod

Cut sod bricks, called clumps, can be used to make strong, long-lasting walls. The clod is cut from soil that has a thick layer of grass roots, which can be found in the soils at the bottom of rivers. It is laid on its edge to dry before being used in construction.[12] European settlers of the North American prairies discovered that the sod least likely to deteriorate from frost or rain came from dry mudflats.[15] In Ireland, Scotland, and Iceland, where some sod houses can still be found, this material was widely used in the walls of houses. A sod house can last fifty years or more if well maintained in a cold climate.[16]​ Icelanders consider the best quality grass to be Strengur, the top 5 centimeters of the sod.[17]​.

stabilized land

Clay is usually hard and strong when dry, but becomes very soft when it absorbs water. Dry clay helps hold an earthen wall together, but if the wall is directly exposed to rain or water seeping from the roof, it can become saturated.[18] Soil can be "stabilized" to make it more weather-resistant. The practice of stabilizing soil by adding burnt lime is centuries old.[19]​ Portland cement or bitumen can also be added to soil intended for construction, which adds strength, although stabilized soil is not as strong as fired clay or concrete.[19]​ Mixtures of cement and lime, or pozzolana and lime, can also be used for stabilization.[20]​.

Preferably, the sand content of the soil will be 65%-75%. Soils with low clay content, or with no more than 15% non-expansive clay, are suitable for stabilized soil.[21]​ The percentage of clay can be reduced by adding sand, if available.[22]​ If there is more than 15% clay it may require more than 10% cement to stabilize the soil, which increases the cost.[21]​ If the soil is low in clay and contains 10% or more cement, It is indeed concrete. Cement is not particularly environmentally friendly, as the manufacturing process generates large amounts of carbon dioxide.[23] Low-density stabilized soil will be porous and weak. Therefore, the soil must be compacted either with a block-making machine or within the wall using the "rammed earth" technique.[20]​

rammed earth

Rammed earth is a wall construction technique that uses natural raw materials such as earth, chalk ("Crete (rock)"), lime "Lime (material)") or gravel. Rammed earth walls are constructed by placing moist soil in a temporary formwork. The earth is compacted manually or mechanically and then the formwork is removed.[24] Rammed earth is usually made without much water, so it does not need much time to dry as the building is erected. It is susceptible to moisture, so it must be placed on a layer that prevents the rise of moisture, it must be roofed or covered to prevent the entry of water from above and may need protection by some type of plaster, paint or coating.[23]​.

In China, rammed earth walls were built by the Longshan people between 2600 and 1900 BC. C., during the period in which the first cities appeared in the region. Thick sloping walls of rammed earth became a feature of traditional Buddhist monasteries throughout the Himalayas and became very common in areas of northern India such as Sikkim. The technique spread to the Middle East and North Africa and the city of Carthage was built with rammed earth. From there, the Romans brought the technology to Europe.[26] Rammed earth structures can be durable. Most of the Great Wall of China was built with rammed earth, as was the Alhambra in the Kingdom of Granada. In northern Europe there are rammed earth buildings up to seven stories high and two hundred years old.[23]​.

Concrete

The Romans made durable concrete, strong enough to support load-bearing walls.[27]​ The mortar included lime and pozzolana, a volcanic material that contributed significantly to its strength.[28]​ Roman concrete structures, such as the Colosseum, completed in 80 AD. C., they still stand.[29]​ Their longevity can be explained by the fact that builders used a relatively dry mixture of mortar and aggregates and compacted it by beating to eliminate air pockets.[30]​ Although derived from earth products, concrete structures are not usually considered earth structures.[31]​.

Mud brick or adobe

Adobes or mud bricks are preformed modular units of sun-dried mud masonry that were invented at different times in different parts of the world as civilization developed.[32] Brick construction avoids delays while each course of puddled mud dries. Wall paintings show that adobe production techniques were highly advanced in Egypt around 2500 BC. C..[12]​ Adobe construction is common in much of Africa today.[33]​ Adobe bricks are traditionally made from sand and clay mixed with water to a plastic consistency, with straw or grass as a binder.[34]​[note 4]​ The mud is prepared, placed in wooden molds, tamped and leveled, and then removed from the mold to dry for several days. The bricks are then set on edge to air-cure for a month or more.[34]​.

In the southwestern United States and Mexico, adobe buildings had solid walls and rarely exceeded two stories in height. The adobe churches of the missions never exceeded 11 m.[36] As adobe surfaces are fragile, coatings are used to protect them. These coatings, periodically renewed, have included mud plaster, lime plaster, whitewash[note 5]​ or stucco.[37]​ Historically, adobe walls were built by laying the bricks with mud mortar, which swells and shrinks at the same rate as the bricks when they are wet or dry, heated or cooled. Modern adobe can be stabilized with cement and joined with cement mortars, but cement mortars will cause deterioration of unstabilized adobe bricks due to different rates of thermal expansion and contraction.[36]​.

Compressed earth block

Traditionally, compressed earth blocks were made by pushing earth into a wooden mold with a stick. Nowadays they are usually made with subsoil soil compressed in a manual or motorized machine. In the developing world, manual machines can be a cost-effective solution for making uniform building blocks, while more complex and expensive motorized machines are less appropriate. Although labor intensive, construction with compressed earth blocks avoids the costs of purchasing and transporting materials.[38] Block making machines can form blocks into interlocking shapes to reduce the need for mortar. The block may have holes or slots to insert rods, such as bamboo, to improve earthquake resistance.[39]​.

Suitable soil should be used, with enough clay to hold the block together and resist erosion, but without too much expansive clay.[40] When the block has been made from stabilized soil, which contains cement, the concrete should be given about three weeks to cure. During this time, the blocks should be stacked and prevented from drying out by spraying them with water. This can be a problem in hot, dry climates where water is scarce. Stacking the blocks closely and covering them with a polyethylene sheet can help reduce water loss.[41]​.

bags of earth

Earthbag construction is a natural construction technique that has evolved from historical military bunker construction techniques.[42] Local subsoil of almost any composition can be used, although an adobe mix would be preferable. The soil is moistened so that it compacts and forms a stable structure when packed into woven polypropylene or burlap bags or tubes. Sometimes plastic mesh is used. Polypropylene bags are the most common, as they are durable when covered, cheap, and widely available.[42]​ The bags are laid in rows, with barbed wire between each row to prevent slipping, and each row is tamped after laying.[43]​ The structure of PP bags is similar to that of adobe, but more flexible. The structure of pp bags is similar to that of adobe, but more flexible. With mesh tubes, the structure is similar to rammed earth.[42] Earthbags can be used to construct dome-shaped buildings or buildings with vertical walls. With soil stabilization they can also be used for retaining walls.[44]​.

Baked clay brick

The technique of firing clay bricks in a kiln dates back to 3500 BC. C. approximately. Burnt bricks were used to build durable masonry throughout Europe, Asia and North Africa by 1200 BC. C. and remain an important building material.[45] Modern fired clay bricks are formed from clays or slates, which are shaped and then fired in a kiln for 8-12 hours at a temperature of 900-1150 °C.[46][note 6]​ The result is a ceramic composed mainly of silica and alumina, with other ingredients such as quartz sand. The porosity of the brick depends on the materials and the temperature and duration of firing. Bricks can vary in color depending on the amount of iron and calcium carbonate in the materials used and the amount of oxygen in the kiln.[46]​ Bricks can deteriorate due to the crystallization of salts in the brick or in its pores, the action of frost and acid gases.[49]​.

The bricks are laid in courses held together with mortar, a combination of Portland cement, lime and sand. There are several types of rigging "ligatures" ("Rigging (construction)"), such as English, Dutch and Flemish.[51]​.

earth shelter

Earth shelters have been used for thousands of years to build energy-efficient homes.[52]​ At one extreme, an earth house is completely underground, perhaps with an open courtyard to provide air and light. An earthen shelter may be situated on a hillside, with windows or doors on one or more sides, or the building may be at ground level, but with earth piled against the walls and perhaps with an earthen roof.[53]

The pit houses built by Hohokam farmers between AD 100 and 900. C., in what is now the southwestern United States, were bermed structures, partially embedded in south-facing slopes. Its successful design was used for hundreds of years.[54]​ In Matmata (Tunisia), most ancient houses were built 12 meters (39 ft) below ground level and surrounded courtyards of about 12 meters (39 ft) square.[55][note 7]​ The houses were accessed through tunnels. Other examples of subterranean, semi-subterranean, or cliff dwellings, in both hot and cold climates, are found in Turkey, northern China, and the Himalayas and southwestern United States.[55] Various Buddhist monasteries built of earth and other materials on the sides of cliffs or caves in Himalayan areas such as Tibet, Bhutan, Nepal, and northern India are often found in dangerous locations. Since the 1970s, interest in this technique has resurfaced in developed countries.[52]​ By setting an earthen house on the ground, the house will be cooler in the warm season and warmer in the cold season.[53]​.

Native American Ground Cabin

An earthen hut") is a circular building built by some of the Native Americans of North America. They are dome-shaped and constructed of wooden posts and beams. Exterior transverse beams and then planks or split beams formed the inclined or vertical side walls.[58] The structure was covered with sticks and brush or grass, in turn covered by a thick layer of earth or sod. Some groups plastered the entire structure with mud, which when dried formed a shell.[58]

Bahareque

Bahareque is an ancient construction technique in which vines or smaller sticks are woven between vertical posts and then the wall is covered with mud mixed with straw and grass.[59]​ This technique is found throughout the world, from the Nile Delta to Japan, where bamboo was used to make bahareque.[60]​ In Cahokia, now in Illinois (United States), bahareque houses were built with the soil at a depth of between 0.30 and 0.91 meters below the ground. A variant of this technique is called bajareque in Colombia.[59]​ In prehistoric Britain, simple circular shelters of bahareque were built wherever sufficient clay was available.[61]​ Bahareque is still found as a panel in timber-framed buildings.[62]​ In general, the walls are non-structural and, in interior use, the technique was replaced in the developed world by lath and plaster and, later, by plasterboard.[60]​.

Sod house on the meadow

Pioneer European farmers on the North American prairies, where there was no wood for construction, often built their first home in a cave dug into the side of a hill or ravine, with a cover over the entrance. When they had time, they built a sod house. The farmer used a plow to cut the grass into 1 by 2 foot (0.30 by 0.61 meter) bricks, which were then stacked to form the walls.[63] The strips of sod were stacked grass side down, staggered in the same manner as masonry, in three rows side by side, resulting in a wall more than 0.91 meters thick. The wall was built around the door and window frames and the corners were secured with rods nailed vertically. The roof was made of sticks or brush, covered with prairie grass, and sealed with a layer of sod.[64] Sod houses were durable and usually lasted for many years, but they were damp and dirty unless the interior walls were plastered.[63] The roofs often leaked and sometimes collapsed in storms.[64]

adobe buildings

There are countless examples of adobe or mud brick constructions around the world. The walled city of Shibam in Yemen, declared a World Heritage Site in 1982, is known for its ten-story unreinforced adobe buildings.[65] The Djinguereber Mosque in Timbuktu, Mali, was first built in the early 1900s. C. (1st century AD) with round adobe bricks and a mixture of stone and mud and was subsequently rebuilt several times, constantly increasing in size(62).[66] Further south in Mali, the Great Mosque of Djenné, a spectacular example of Sahelian adobe architecture, was built in 1907 on the design of an earlier Great Mosque, built on the same site in 1280. The adobe requires maintenance and the fundamentalist ruler Seku Amadu had allowed the previous mosque to collapse.[67]​.

The Big House ruins, now an Arizona national monument protected by a modern roof, are a massive four-story adobe structure built by the Hohokam between 1200 and 1450 AD. C.[68]​ The first European to record the great house was a Jesuit priest, Father Eusebio Kino, who visited the place in 1694. At that time it had been abandoned for a long time.[69]​ When a temporary roof was installed in 1903, the adobe building had been empty and unmaintained for hundreds of years(66).[70]​.

The Huaca de la Luna, in what is now northern Peru, is a large adobe temple built by the Moche people. The building went through a series of construction phases, eventually growing to a height of around 32 metres, with three main platforms, four plazas and many smaller rooms and enclosures. The walls were covered in striking multicolored murals and friezes; Those that can be seen today date from between 400 and 610 AD. C..[71]​.

Tulous

A Fujian tulou is a type of rural dwelling of the Hakka people in the mountainous areas of southeastern Fujian, China.[72] They were built primarily between the 13th and 20th centuries.[73] A tulou is a large, enclosed and fortified earthen building, rectangular or circular, with thick load-bearing walls of rammed earth between three and five stories high. A tulou can accommodate up to 80 families. Smaller interior buildings are usually surrounded by these huge peripheral walls, which may contain rooms, warehouses, wells, and living quarters. The structure resembles a small fortified city.[74]​ The walls are formed by compacting earth mixed with stone, bamboo, wood and other readily available materials and are up to 1.8 meters thick. The result is a building that is well lit, well ventilated, wind and earthquake proof, warm in winter and cool in summer.[74]​.

Tumuli and pyramids

Ziggurats were elevated temples built by the Sumerians between the end of the 4th millennium BC. C. and the II millennium BC. C., which rose in a series of terraces until reaching a height of 61 meters above ground level. The Ziggurat of Ur contained some three million bricks, none of them more than 15 inches (380 mm) in length, so its construction must have been an enormous project.[75] The largest ziggurat was in Babylon and is believed by some to be the Tower of Babel mentioned in the Bible. It was destroyed by Alexander the Great and only the foundations remain, but it was originally 91 meters high on a base of 200 square meters.[76] Sun-dried bricks were used for the interior and baked bricks for the cladding. The bricks were joined with clay or bitumen.[77]​.

Many pre-Columbian indigenous societies of ancient North America built large earthen pyramidal structures known as platform mounds. Among the largest and best-known of these structures is the Monk's Mound, at the site of Cahokia, in what became Illinois, completed around 1100 AD. C., whose base is larger than that of the Great Pyramid of Giza. Many of the mounds were built several times at periodic intervals and some became quite large. They are believed to have played a central role in the religious life of the mound-building peoples and documented uses include semi-public platforms for the chief's house, platforms for public temples, mortuary platforms, platforms for ossuaries, platforms for earthen hut lodges, platforms for residence platforms, platforms for plazas and rotundas, and platforms for dances.[78]​[79]​.

The Pyramid of the Sun of Teotihuacán (Mexico), 63 meters high, began to be built in the year 100 AD. C.. The stone structure contains two million tons of rammed earth.[26]​.

Earthworks

Earthworks "Earth works (archaeology)") are engineering works created by moving or processing quantities of unformed earth or rock. The material can be moved to another location and molded to the desired shape.[80]​ Dikes, embankments, and dams are types of earthworks. A dike, check dam or check dam is an elongated natural ridge or artificially constructed earthen wall that regulates the water level. It is usually made of land and runs parallel to the course of a river in its flood plain or along low coasts.[81]​.

Mechanically stabilized earth (MSE) retaining walls can be used for embankments.[82]​ Mechanically stabilized earth walls combine a concrete leveling pad, wall covering panels, coping, soil reinforcement and selected fill.[83]​ Various designs of wall covering panels can be used.[83]​ Once the leveling pad and the first row of panels are in place, the first layer of fill can be used.[83]​ of earth is placed behind the wall and compacted. The first set of reinforcements is then placed on top of the soil.[84]​ The reinforcements, which may be strips or grids of tensioned polymer or galvanized metal, are attached to the siding panels.[85]​ This process is repeated with successive layers of panels, soil, and reinforcements. In this way, the panels are tied to the earth embankment to form a stable structure with balanced stresses.[86]​.

Although construction using the basic principles of mechanically stabilized earth has a long history, it was developed in its current form in the 1960s. The reinforcing elements used can vary, but include steel and geosynthetics. The term MSE is commonly used in the US to distinguish it from "Reinforced Earth", the trade name of the Reinforced Earth Company, but elsewhere Reinforced Soil is the generally accepted term.[82] Construction with mechanically stabilized earth is relatively quick and cheap and although labor intensive, does not require high levels of skill. Therefore, it is suitable for both developing and developed countries.[87]​.

Forts and trenches

The land has been used to build fortifications for thousands of years, including fortresses and walls, often protected by ditches. Aerial photography in Europe has revealed traces of earthen fortifications from Roman times and later medieval times.[88] Offa's Dyke is a massive embankment that runs along the disputed border between England and Wales.[89]Little is known about the era or the builder, King Offa of Mercia**,** who died in 796 AD. C.[90]​ A primitive fortification of wood and earth could be later succeeded by a brick or stone structure in the same location.[91]​.

The trenches were used by the besieging forces to approach a fortification protected from projectiles. The sappers built "saps" or trenches, which zigzagged towards the attacked fortress. They piled up the excavated earth to form a protective wall or gabion. The combined depth of the trench and height of the gabion could be 2.4 to 3.0 meters (8 to 10 feet). Sometimes the sap was a tunnel dug several meters below the surface. The sappers were highly skilled and well paid due to the extreme danger of their work.[92]​.

In the American Civil War (1861-1865), trenches were used as defensive positions throughout the war, but played an increasingly important role in the campaigns of the last two years.[93] Military earthworks perhaps culminated in the vast network of trenches built during World War I (1914-1918), which extended from Switzerland to the North Sea in late 1914.[94] The two lines of trenches faced each other, manned by soldiers who lived in terrible conditions of cold, humidity and dirt.[95] Conditions were worse in the Allied trenches. The Germans were more willing to accept trenches as long-term positions and used concrete blocks to build safe shelters underground, often with electric lighting and heating.[96]

Loose material dams

A loose material dam is a huge artificial barrier against water. It is usually created by emplacement and compaction of a complex semi-plastic mound "Plasticity (solid mechanics)") of various compositions of soil, sand, clay and/or rock. It has a semi-permanent natural waterproof coating on its surface and a dense, waterproof core. This makes the dam impermeable to surface erosion or infiltration.[97] The force of the reservoir creates a downward thrust on the mass of the dam, greatly increasing the weight of the dam on its foundations. This added force effectively seals and waterproofs the underlying foundation of the dam, at the interface between the dam and its channel.[98]​ A dam of this type is composed of fragmented independent particles of material. Friction and the interaction of the particles bind them together into a stable mass instead of using a cementing substance.[99]​.

The Syncrude Tailings tailings dam, in Alberta (Canada), is a check dam approximately 18 kilometers long and between 40 and 88 meters high. In 2001 it was considered the largest earth structure in the world by volume of fill.[100]​.

Design for earthquakes

Low seismic risk regions are safe for most earthen buildings, but historic construction techniques often cannot effectively resist even medium seismic levels due to the three highly undesirable qualities of earthen buildings as a seismic construction material: being relatively "weak, heavy and brittle". However, earthen buildings can be constructed to resist seismic loads.[101]​.

The key factors to improve seismic performance are soil resistance, construction quality, solidity of the layout and seismic reinforcement.[102]​.

Stronger soils make stronger walls. Adobe builders can test the strength of cured blocks by dropping them from a certain height or breaking them with a pry bar. Builders using immediate techniques such as earth bags, cob, or rammed earth may prefer to perform rough crush tests on smaller samples that can be kiln dried and crushed with a small pry bar.

Builders must understand construction processes and be able to produce solid buildings of consistent quality.[105]​.

A robust layout implies buildings that are more square than elongated, symmetrical and not L-shaped,[106]​ as well as that the first floors are not "soft" (floors with large windows, buildings on unbraced columns). New Zealand earth building guidelines check that the length of bracing walls is sufficient in each of the two main directions, based on the thickness of the walls, the height of the floors, the spacing of the bracing walls and the weight of the roof, attic and second floor above the earth walls.[107]​.

Anti-seismic construction techniques

Construction techniques that are more ductile than brittle, such as the soil-contained type of earthbags or the tire walls of earthships, may be better at preventing collapse than unreinforced brittle earth. Base layers of contained gravel can add foundation insulation potential.

Retaining walls can be added to techniques such as adobe to resist material loss leading to collapse(104). Confined masonry is effective for adobe against seismic forces of 0.3 g[108]​[109]​ may be useful with earthen masonry.

Many types of reinforcement can increase the strength of walls, such as plastic or wire mesh and steel or fiberglass or bamboo reinforcing rods. Earth resists compression well but is weak when twisted. Tensile reinforcement should span potential damage points and be well anchored to increase out-of-plane stability. The tie beams at the top of the walls are vital and must be securely fastened to the walls.[101]​.

Builders should be aware that organic reinforcements embedded in walls may be destroyed before the building is removed. The reinforcement fixing details are essential to resist higher forces. The best shear strength of adobe came from horizontal reinforcements attached directly to vertical reinforcement bars extending from the footing to the tie beam.[110]​.

Interlocking wood in earthen walls reduces earthquake damage if the wood is not damaged by dry rot or insects. Timber framing includes fine-framed Dhajji,[111]​ and other types.[112]​.

Contenido

La tierra suele requerir algún tipo de procesamiento para su uso en la construcción. Puede combinarse con agua para hacer barro, puede añadirse paja, puede utilizarse algún tipo de material estabilizador como cal o cemento para endurecer la tierra y puede compactarse para aumentar su resistencia.[9]​.

Mud

Adobe construction is one of the oldest methods of building walls. Wet clay is shaped by hand to form the base of a wall and left to dry. More mud is added and left to dry to form successive courses until the wall is completed. In the case of soaked mud, a handmade mold is filled with wetter clay and allowed to dry.[10]​ In Iran, soaked mud walls are called chine construction. Each course has a thickness of 460 to 610 mm and a height of 460 to 610 mm. This technique is often used in garden walls, but not in house construction, presumably because of concerns about the strength of walls constructed in this way.[11]​ A disadvantage of this method is that a lot of time can be wasted waiting for each course to dry.[12]​ Another technique, used in areas where wood is abundant, is to build a wood-frame house and fill it with mud, mainly to insulate it. In some areas of England a similar technique was used with cob.[10]​.

cob

Adobe, sometimes called "monolithic adobe",[13]​ is a natural building material made of earth that includes clay, sand or small stones, and an organic material such as straw. Adobe walls are usually built in courses, have no mortar joints, and require 30% or more clay in the soil. It can be used as fill in post-and-beam buildings, but is often used for load-bearing walls and can support up to two stories. A cob wall must have a minimum thickness of 410 mm and the ratio between width and height must not exceed one in ten.[13]​ It is normally plastered inside and out with a mixture of lime, earth and sand. Cob is fireproof and its thermal mass helps stabilize interior temperatures.[13] Tests have shown that cob has some resistance to seismic activity. However, building codes in developed countries may not recognize cob as an approved material.[14]​.

sod or clod

Cut sod bricks, called clumps, can be used to make strong, long-lasting walls. The clod is cut from soil that has a thick layer of grass roots, which can be found in the soils at the bottom of rivers. It is laid on its edge to dry before being used in construction.[12] European settlers of the North American prairies discovered that the sod least likely to deteriorate from frost or rain came from dry mudflats.[15] In Ireland, Scotland, and Iceland, where some sod houses can still be found, this material was widely used in the walls of houses. A sod house can last fifty years or more if well maintained in a cold climate.[16]​ Icelanders consider the best quality grass to be Strengur, the top 5 centimeters of the sod.[17]​.

stabilized land

Clay is usually hard and strong when dry, but becomes very soft when it absorbs water. Dry clay helps hold an earthen wall together, but if the wall is directly exposed to rain or water seeping from the roof, it can become saturated.[18] Soil can be "stabilized" to make it more weather-resistant. The practice of stabilizing soil by adding burnt lime is centuries old.[19]​ Portland cement or bitumen can also be added to soil intended for construction, which adds strength, although stabilized soil is not as strong as fired clay or concrete.[19]​ Mixtures of cement and lime, or pozzolana and lime, can also be used for stabilization.[20]​.

Preferably, the sand content of the soil will be 65%-75%. Soils with low clay content, or with no more than 15% non-expansive clay, are suitable for stabilized soil.[21]​ The percentage of clay can be reduced by adding sand, if available.[22]​ If there is more than 15% clay it may require more than 10% cement to stabilize the soil, which increases the cost.[21]​ If the soil is low in clay and contains 10% or more cement, It is indeed concrete. Cement is not particularly environmentally friendly, as the manufacturing process generates large amounts of carbon dioxide.[23] Low-density stabilized soil will be porous and weak. Therefore, the soil must be compacted either with a block-making machine or within the wall using the "rammed earth" technique.[20]​

rammed earth

Rammed earth is a wall construction technique that uses natural raw materials such as earth, chalk ("Crete (rock)"), lime "Lime (material)") or gravel. Rammed earth walls are constructed by placing moist soil in a temporary formwork. The earth is compacted manually or mechanically and then the formwork is removed.[24] Rammed earth is usually made without much water, so it does not need much time to dry as the building is erected. It is susceptible to moisture, so it must be placed on a layer that prevents the rise of moisture, it must be roofed or covered to prevent the entry of water from above and may need protection by some type of plaster, paint or coating.[23]​.

In China, rammed earth walls were built by the Longshan people between 2600 and 1900 BC. C., during the period in which the first cities appeared in the region. Thick sloping walls of rammed earth became a feature of traditional Buddhist monasteries throughout the Himalayas and became very common in areas of northern India such as Sikkim. The technique spread to the Middle East and North Africa and the city of Carthage was built with rammed earth. From there, the Romans brought the technology to Europe.[26] Rammed earth structures can be durable. Most of the Great Wall of China was built with rammed earth, as was the Alhambra in the Kingdom of Granada. In northern Europe there are rammed earth buildings up to seven stories high and two hundred years old.[23]​.

Concrete

The Romans made durable concrete, strong enough to support load-bearing walls.[27]​ The mortar included lime and pozzolana, a volcanic material that contributed significantly to its strength.[28]​ Roman concrete structures, such as the Colosseum, completed in 80 AD. C., they still stand.[29]​ Their longevity can be explained by the fact that builders used a relatively dry mixture of mortar and aggregates and compacted it by beating to eliminate air pockets.[30]​ Although derived from earth products, concrete structures are not usually considered earth structures.[31]​.

Mud brick or adobe

Adobes or mud bricks are preformed modular units of sun-dried mud masonry that were invented at different times in different parts of the world as civilization developed.[32] Brick construction avoids delays while each course of puddled mud dries. Wall paintings show that adobe production techniques were highly advanced in Egypt around 2500 BC. C..[12]​ Adobe construction is common in much of Africa today.[33]​ Adobe bricks are traditionally made from sand and clay mixed with water to a plastic consistency, with straw or grass as a binder.[34]​[note 4]​ The mud is prepared, placed in wooden molds, tamped and leveled, and then removed from the mold to dry for several days. The bricks are then set on edge to air-cure for a month or more.[34]​.

In the southwestern United States and Mexico, adobe buildings had solid walls and rarely exceeded two stories in height. The adobe churches of the missions never exceeded 11 m.[36] As adobe surfaces are fragile, coatings are used to protect them. These coatings, periodically renewed, have included mud plaster, lime plaster, whitewash[note 5]​ or stucco.[37]​ Historically, adobe walls were built by laying the bricks with mud mortar, which swells and shrinks at the same rate as the bricks when they are wet or dry, heated or cooled. Modern adobe can be stabilized with cement and joined with cement mortars, but cement mortars will cause deterioration of unstabilized adobe bricks due to different rates of thermal expansion and contraction.[36]​.

Compressed earth block

Traditionally, compressed earth blocks were made by pushing earth into a wooden mold with a stick. Nowadays they are usually made with subsoil soil compressed in a manual or motorized machine. In the developing world, manual machines can be a cost-effective solution for making uniform building blocks, while more complex and expensive motorized machines are less appropriate. Although labor intensive, construction with compressed earth blocks avoids the costs of purchasing and transporting materials.[38] Block making machines can form blocks into interlocking shapes to reduce the need for mortar. The block may have holes or slots to insert rods, such as bamboo, to improve earthquake resistance.[39]​.

Suitable soil should be used, with enough clay to hold the block together and resist erosion, but without too much expansive clay.[40] When the block has been made from stabilized soil, which contains cement, the concrete should be given about three weeks to cure. During this time, the blocks should be stacked and prevented from drying out by spraying them with water. This can be a problem in hot, dry climates where water is scarce. Stacking the blocks closely and covering them with a polyethylene sheet can help reduce water loss.[41]​.

bags of earth

Earthbag construction is a natural construction technique that has evolved from historical military bunker construction techniques.[42] Local subsoil of almost any composition can be used, although an adobe mix would be preferable. The soil is moistened so that it compacts and forms a stable structure when packed into woven polypropylene or burlap bags or tubes. Sometimes plastic mesh is used. Polypropylene bags are the most common, as they are durable when covered, cheap, and widely available.[42]​ The bags are laid in rows, with barbed wire between each row to prevent slipping, and each row is tamped after laying.[43]​ The structure of PP bags is similar to that of adobe, but more flexible. The structure of pp bags is similar to that of adobe, but more flexible. With mesh tubes, the structure is similar to rammed earth.[42] Earthbags can be used to construct dome-shaped buildings or buildings with vertical walls. With soil stabilization they can also be used for retaining walls.[44]​.

Baked clay brick

The technique of firing clay bricks in a kiln dates back to 3500 BC. C. approximately. Burnt bricks were used to build durable masonry throughout Europe, Asia and North Africa by 1200 BC. C. and remain an important building material.[45] Modern fired clay bricks are formed from clays or slates, which are shaped and then fired in a kiln for 8-12 hours at a temperature of 900-1150 °C.[46][note 6]​ The result is a ceramic composed mainly of silica and alumina, with other ingredients such as quartz sand. The porosity of the brick depends on the materials and the temperature and duration of firing. Bricks can vary in color depending on the amount of iron and calcium carbonate in the materials used and the amount of oxygen in the kiln.[46]​ Bricks can deteriorate due to the crystallization of salts in the brick or in its pores, the action of frost and acid gases.[49]​.

The bricks are laid in courses held together with mortar, a combination of Portland cement, lime and sand. There are several types of rigging "ligatures" ("Rigging (construction)"), such as English, Dutch and Flemish.[51]​.

earth shelter

Earth shelters have been used for thousands of years to build energy-efficient homes.[52]​ At one extreme, an earth house is completely underground, perhaps with an open courtyard to provide air and light. An earthen shelter may be situated on a hillside, with windows or doors on one or more sides, or the building may be at ground level, but with earth piled against the walls and perhaps with an earthen roof.[53]

The pit houses built by Hohokam farmers between AD 100 and 900. C., in what is now the southwestern United States, were bermed structures, partially embedded in south-facing slopes. Its successful design was used for hundreds of years.[54]​ In Matmata (Tunisia), most ancient houses were built 12 meters (39 ft) below ground level and surrounded courtyards of about 12 meters (39 ft) square.[55][note 7]​ The houses were accessed through tunnels. Other examples of subterranean, semi-subterranean, or cliff dwellings, in both hot and cold climates, are found in Turkey, northern China, and the Himalayas and southwestern United States.[55] Various Buddhist monasteries built of earth and other materials on the sides of cliffs or caves in Himalayan areas such as Tibet, Bhutan, Nepal, and northern India are often found in dangerous locations. Since the 1970s, interest in this technique has resurfaced in developed countries.[52]​ By setting an earthen house on the ground, the house will be cooler in the warm season and warmer in the cold season.[53]​.

Native American Ground Cabin

An earthen hut") is a circular building built by some of the Native Americans of North America. They are dome-shaped and constructed of wooden posts and beams. Exterior transverse beams and then planks or split beams formed the inclined or vertical side walls.[58] The structure was covered with sticks and brush or grass, in turn covered by a thick layer of earth or sod. Some groups plastered the entire structure with mud, which when dried formed a shell.[58]

Bahareque

Bahareque is an ancient construction technique in which vines or smaller sticks are woven between vertical posts and then the wall is covered with mud mixed with straw and grass.[59]​ This technique is found throughout the world, from the Nile Delta to Japan, where bamboo was used to make bahareque.[60]​ In Cahokia, now in Illinois (United States), bahareque houses were built with the soil at a depth of between 0.30 and 0.91 meters below the ground. A variant of this technique is called bajareque in Colombia.[59]​ In prehistoric Britain, simple circular shelters of bahareque were built wherever sufficient clay was available.[61]​ Bahareque is still found as a panel in timber-framed buildings.[62]​ In general, the walls are non-structural and, in interior use, the technique was replaced in the developed world by lath and plaster and, later, by plasterboard.[60]​.

Sod house on the meadow

Pioneer European farmers on the North American prairies, where there was no wood for construction, often built their first home in a cave dug into the side of a hill or ravine, with a cover over the entrance. When they had time, they built a sod house. The farmer used a plow to cut the grass into 1 by 2 foot (0.30 by 0.61 meter) bricks, which were then stacked to form the walls.[63] The strips of sod were stacked grass side down, staggered in the same manner as masonry, in three rows side by side, resulting in a wall more than 0.91 meters thick. The wall was built around the door and window frames and the corners were secured with rods nailed vertically. The roof was made of sticks or brush, covered with prairie grass, and sealed with a layer of sod.[64] Sod houses were durable and usually lasted for many years, but they were damp and dirty unless the interior walls were plastered.[63] The roofs often leaked and sometimes collapsed in storms.[64]

adobe buildings

There are countless examples of adobe or mud brick constructions around the world. The walled city of Shibam in Yemen, declared a World Heritage Site in 1982, is known for its ten-story unreinforced adobe buildings.[65] The Djinguereber Mosque in Timbuktu, Mali, was first built in the early 1900s. C. (1st century AD) with round adobe bricks and a mixture of stone and mud and was subsequently rebuilt several times, constantly increasing in size(62).[66] Further south in Mali, the Great Mosque of Djenné, a spectacular example of Sahelian adobe architecture, was built in 1907 on the design of an earlier Great Mosque, built on the same site in 1280. The adobe requires maintenance and the fundamentalist ruler Seku Amadu had allowed the previous mosque to collapse.[67]​.

The Big House ruins, now an Arizona national monument protected by a modern roof, are a massive four-story adobe structure built by the Hohokam between 1200 and 1450 AD. C.[68]​ The first European to record the great house was a Jesuit priest, Father Eusebio Kino, who visited the place in 1694. At that time it had been abandoned for a long time.[69]​ When a temporary roof was installed in 1903, the adobe building had been empty and unmaintained for hundreds of years(66).[70]​.

The Huaca de la Luna, in what is now northern Peru, is a large adobe temple built by the Moche people. The building went through a series of construction phases, eventually growing to a height of around 32 metres, with three main platforms, four plazas and many smaller rooms and enclosures. The walls were covered in striking multicolored murals and friezes; Those that can be seen today date from between 400 and 610 AD. C..[71]​.

Tulous

A Fujian tulou is a type of rural dwelling of the Hakka people in the mountainous areas of southeastern Fujian, China.[72] They were built primarily between the 13th and 20th centuries.[73] A tulou is a large, enclosed and fortified earthen building, rectangular or circular, with thick load-bearing walls of rammed earth between three and five stories high. A tulou can accommodate up to 80 families. Smaller interior buildings are usually surrounded by these huge peripheral walls, which may contain rooms, warehouses, wells, and living quarters. The structure resembles a small fortified city.[74]​ The walls are formed by compacting earth mixed with stone, bamboo, wood and other readily available materials and are up to 1.8 meters thick. The result is a building that is well lit, well ventilated, wind and earthquake proof, warm in winter and cool in summer.[74]​.

Tumuli and pyramids

Ziggurats were elevated temples built by the Sumerians between the end of the 4th millennium BC. C. and the II millennium BC. C., which rose in a series of terraces until reaching a height of 61 meters above ground level. The Ziggurat of Ur contained some three million bricks, none of them more than 15 inches (380 mm) in length, so its construction must have been an enormous project.[75] The largest ziggurat was in Babylon and is believed by some to be the Tower of Babel mentioned in the Bible. It was destroyed by Alexander the Great and only the foundations remain, but it was originally 91 meters high on a base of 200 square meters.[76] Sun-dried bricks were used for the interior and baked bricks for the cladding. The bricks were joined with clay or bitumen.[77]​.

Many pre-Columbian indigenous societies of ancient North America built large earthen pyramidal structures known as platform mounds. Among the largest and best-known of these structures is the Monk's Mound, at the site of Cahokia, in what became Illinois, completed around 1100 AD. C., whose base is larger than that of the Great Pyramid of Giza. Many of the mounds were built several times at periodic intervals and some became quite large. They are believed to have played a central role in the religious life of the mound-building peoples and documented uses include semi-public platforms for the chief's house, platforms for public temples, mortuary platforms, platforms for ossuaries, platforms for earthen hut lodges, platforms for residence platforms, platforms for plazas and rotundas, and platforms for dances.[78]​[79]​.

The Pyramid of the Sun of Teotihuacán (Mexico), 63 meters high, began to be built in the year 100 AD. C.. The stone structure contains two million tons of rammed earth.[26]​.

Earthworks

Earthworks "Earth works (archaeology)") are engineering works created by moving or processing quantities of unformed earth or rock. The material can be moved to another location and molded to the desired shape.[80]​ Dikes, embankments, and dams are types of earthworks. A dike, check dam or check dam is an elongated natural ridge or artificially constructed earthen wall that regulates the water level. It is usually made of land and runs parallel to the course of a river in its flood plain or along low coasts.[81]​.

Mechanically stabilized earth (MSE) retaining walls can be used for embankments.[82]​ Mechanically stabilized earth walls combine a concrete leveling pad, wall covering panels, coping, soil reinforcement and selected fill.[83]​ Various designs of wall covering panels can be used.[83]​ Once the leveling pad and the first row of panels are in place, the first layer of fill can be used.[83]​ of earth is placed behind the wall and compacted. The first set of reinforcements is then placed on top of the soil.[84]​ The reinforcements, which may be strips or grids of tensioned polymer or galvanized metal, are attached to the siding panels.[85]​ This process is repeated with successive layers of panels, soil, and reinforcements. In this way, the panels are tied to the earth embankment to form a stable structure with balanced stresses.[86]​.

Although construction using the basic principles of mechanically stabilized earth has a long history, it was developed in its current form in the 1960s. The reinforcing elements used can vary, but include steel and geosynthetics. The term MSE is commonly used in the US to distinguish it from "Reinforced Earth", the trade name of the Reinforced Earth Company, but elsewhere Reinforced Soil is the generally accepted term.[82] Construction with mechanically stabilized earth is relatively quick and cheap and although labor intensive, does not require high levels of skill. Therefore, it is suitable for both developing and developed countries.[87]​.

Forts and trenches

The land has been used to build fortifications for thousands of years, including fortresses and walls, often protected by ditches. Aerial photography in Europe has revealed traces of earthen fortifications from Roman times and later medieval times.[88] Offa's Dyke is a massive embankment that runs along the disputed border between England and Wales.[89]Little is known about the era or the builder, King Offa of Mercia**,** who died in 796 AD. C.[90]​ A primitive fortification of wood and earth could be later succeeded by a brick or stone structure in the same location.[91]​.

The trenches were used by the besieging forces to approach a fortification protected from projectiles. The sappers built "saps" or trenches, which zigzagged towards the attacked fortress. They piled up the excavated earth to form a protective wall or gabion. The combined depth of the trench and height of the gabion could be 2.4 to 3.0 meters (8 to 10 feet). Sometimes the sap was a tunnel dug several meters below the surface. The sappers were highly skilled and well paid due to the extreme danger of their work.[92]​.

In the American Civil War (1861-1865), trenches were used as defensive positions throughout the war, but played an increasingly important role in the campaigns of the last two years.[93] Military earthworks perhaps culminated in the vast network of trenches built during World War I (1914-1918), which extended from Switzerland to the North Sea in late 1914.[94] The two lines of trenches faced each other, manned by soldiers who lived in terrible conditions of cold, humidity and dirt.[95] Conditions were worse in the Allied trenches. The Germans were more willing to accept trenches as long-term positions and used concrete blocks to build safe shelters underground, often with electric lighting and heating.[96]

Loose material dams

A loose material dam is a huge artificial barrier against water. It is usually created by emplacement and compaction of a complex semi-plastic mound "Plasticity (solid mechanics)") of various compositions of soil, sand, clay and/or rock. It has a semi-permanent natural waterproof coating on its surface and a dense, waterproof core. This makes the dam impermeable to surface erosion or infiltration.[97] The force of the reservoir creates a downward thrust on the mass of the dam, greatly increasing the weight of the dam on its foundations. This added force effectively seals and waterproofs the underlying foundation of the dam, at the interface between the dam and its channel.[98]​ A dam of this type is composed of fragmented independent particles of material. Friction and the interaction of the particles bind them together into a stable mass instead of using a cementing substance.[99]​.

The Syncrude Tailings tailings dam, in Alberta (Canada), is a check dam approximately 18 kilometers long and between 40 and 88 meters high. In 2001 it was considered the largest earth structure in the world by volume of fill.[100]​.

Design for earthquakes

Low seismic risk regions are safe for most earthen buildings, but historic construction techniques often cannot effectively resist even medium seismic levels due to the three highly undesirable qualities of earthen buildings as a seismic construction material: being relatively "weak, heavy and brittle". However, earthen buildings can be constructed to resist seismic loads.[101]​.

The key factors to improve seismic performance are soil resistance, construction quality, solidity of the layout and seismic reinforcement.[102]​.

Stronger soils make stronger walls. Adobe builders can test the strength of cured blocks by dropping them from a certain height or breaking them with a pry bar. Builders using immediate techniques such as earth bags, cob, or rammed earth may prefer to perform rough crush tests on smaller samples that can be kiln dried and crushed with a small pry bar.

Builders must understand construction processes and be able to produce solid buildings of consistent quality.[105]​.

A robust layout implies buildings that are more square than elongated, symmetrical and not L-shaped,[106]​ as well as that the first floors are not "soft" (floors with large windows, buildings on unbraced columns). New Zealand earth building guidelines check that the length of bracing walls is sufficient in each of the two main directions, based on the thickness of the walls, the height of the floors, the spacing of the bracing walls and the weight of the roof, attic and second floor above the earth walls.[107]​.

Anti-seismic construction techniques

Construction techniques that are more ductile than brittle, such as the soil-contained type of earthbags or the tire walls of earthships, may be better at preventing collapse than unreinforced brittle earth. Base layers of contained gravel can add foundation insulation potential.

Retaining walls can be added to techniques such as adobe to resist material loss leading to collapse(104). Confined masonry is effective for adobe against seismic forces of 0.3 g[108]​[109]​ may be useful with earthen masonry.

Many types of reinforcement can increase the strength of walls, such as plastic or wire mesh and steel or fiberglass or bamboo reinforcing rods. Earth resists compression well but is weak when twisted. Tensile reinforcement should span potential damage points and be well anchored to increase out-of-plane stability. The tie beams at the top of the walls are vital and must be securely fastened to the walls.[101]​.

Builders should be aware that organic reinforcements embedded in walls may be destroyed before the building is removed. The reinforcement fixing details are essential to resist higher forces. The best shear strength of adobe came from horizontal reinforcements attached directly to vertical reinforcement bars extending from the footing to the tie beam.[110]​.

Interlocking wood in earthen walls reduces earthquake damage if the wood is not damaged by dry rot or insects. Timber framing includes fine-framed Dhajji,[111]​ and other types.[112]​.