The Great Wall of China is Reinforced by Living Organisms
"There in the mist, enormous, majestic, silent and terrible, stood the Great Wall of China. Solitarily, with the indifference of nature herself, it crept up the mountain side and slipped down to the depth of the valley."
William Somerset Maugham
William Somerset Maugham
A recent study led by Chinese researchers has revealed that biological soil crusts have played a crucial role in safeguarding the Great Wall of China against erosion caused by rain and wind.
The magnificent Great Wall of China owes its structural integrity to the presence of such a thing as the "biocrusts", a combination of living organisms including mosses and lichens that create thin layers of organic materials. These biocrusts, that could be found along large sections of the wall, have played a vital role in safeguarding this architectural wonder from erosion.
Constructed many centuries ago, the Great Wall of China was created with the thought of a protection of the country from external threats. Ancient Chinese workers utilized compressed earth, a mixture of different organic materials: soil and gravel mixed together, to construct the enormous wall. The choice of materials might seem strange at first, since it's more susceptible to erosion when compared to solid stone, it facilitated the growth of biocrusts.
Constructed many centuries ago, the Great Wall of China was created with the thought of a protection of the country from external threats. Ancient Chinese workers utilized compressed earth, a mixture of different organic materials: soil and gravel mixed together, to construct the enormous wall. The choice of materials might seem strange at first, since it's more susceptible to erosion when compared to solid stone, it facilitated the growth of biocrusts.
Biocrusts consist of different cyanobacteria, variety ofo mosses, and lichens, which act as a living stucco reinforcing the structure of the Wall. Especially this helped in dry and semi-dry regions of China.
A recent study that was published in the Science Advances journal has revealed that 67% of all samples taken from different parts of the wall contain biocrusts in them. This study also concludes deliberate use of the clay, sand, lime and many other adhesives to enchance the mechanical strenghts of the materials. These ingredients provided an ideal environment for the growth of organisms that together form biocrusts.
Researchers tested the strenghts of materials and stability of the wall in parts with biocrusts and without. Their findings revealed that samples containing biocrusts were almost three times stronger than one's that used just compressed earth. Crust-containing samples exhibited exceptional strength. This is attributed to the substances secreted by cyanobacteria and other organisms contained in biocrusts, such as polymers, which have an ability to bind tightly with the particles of compressed earth. Essentially this substance acts as cement, strenghtening the structural ability of the wall.
"These cementitious substances, biological filaments, and soil aggregates within the biocrust layer finally form a cohesive network with strong mechanical strength and stability against external erosion," says co-author of the research Bo Xiao, a professor of soil science in the College of Land Science and Technology at China Agricultural University of Beijing.
Interestingly enough, this is not the first use of organic plant materials in building. А team of scientists in Spain previously discovered an ancient Mayan civilization using this technology in their buildings.
A recent study that was published in the Science Advances journal has revealed that 67% of all samples taken from different parts of the wall contain biocrusts in them. This study also concludes deliberate use of the clay, sand, lime and many other adhesives to enchance the mechanical strenghts of the materials. These ingredients provided an ideal environment for the growth of organisms that together form biocrusts.
Researchers tested the strenghts of materials and stability of the wall in parts with biocrusts and without. Their findings revealed that samples containing biocrusts were almost three times stronger than one's that used just compressed earth. Crust-containing samples exhibited exceptional strength. This is attributed to the substances secreted by cyanobacteria and other organisms contained in biocrusts, such as polymers, which have an ability to bind tightly with the particles of compressed earth. Essentially this substance acts as cement, strenghtening the structural ability of the wall.
"These cementitious substances, biological filaments, and soil aggregates within the biocrust layer finally form a cohesive network with strong mechanical strength and stability against external erosion," says co-author of the research Bo Xiao, a professor of soil science in the College of Land Science and Technology at China Agricultural University of Beijing.
Interestingly enough, this is not the first use of organic plant materials in building. А team of scientists in Spain previously discovered an ancient Mayan civilization using this technology in their buildings.
