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生土建筑韧性背后的科学
The Science Behind the Resilience of Earth Architecture

由专筑网Zia，小R编译

建筑的发展有着深远的历史，这些历史故事通过经受住时间考验的古老建筑来讲述。世界各地的生土建筑技术被古代文明所开创，最初用泥土，这是对当时的人们来说最容易获得的材料，而这些建筑技术也世代相传。生土建筑深耕于环境而发扬光大，随着几十年前实践的完善，这些建筑在风雨中仍然保持着性能，这一点非常值得思考。

这些由熟练的建筑工匠所创造的建筑技术，看似是由生土制成的结构，实际上非常耐用。生土建筑是人类最早开发创造庇护所的方法。在今天，大约有三分之一的世界人口生活在由土坯砖石、夯土或鹅卵石制成的结构中，这些结构在世界各地的地震、飓风和极端天气中得以维持。

Earth architecture is built on a far-reaching history. Its story continues to be told through aged structures that have stood the test of time. Across the world, indigenous earth construction techniques have been pioneered by many ancient civilizations. Communities originally built shelters from earth - the most readily available material to them - and have passed on their construction techniques through generations. Earth architecture evolved with a careful understanding of land and location. With practices perfected decades ago, it is fascinating to see earth architecture remaining resilient through adversities
What appears to be a feeble structure made of raw earth is actually very durable, owing to construction techniques fabricated by skilled builders. Earth architecture is considered one of the first methods developed by humans to create shelters. In the present day, around one-third of the world’s population lives in a form of earth structure made of adobe masonry, rammed earth, or cob. These structures have sustained themselves through earthquakes, hurricanes, and extreme weather events across the world.


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古代营造人士深刻理解与土打交道的方式，并世代相传。建设者们已经完善了设计这些地球结构的艺术。虽然各地的建筑方法和建筑形式各不相同，但其韧性背后的科学原理却是跨国界相通的。


颗粒堆积

生土包含各种形状和大小的矿物，这取决于它所处的地区。这种特殊的物质是使生土能够很好地保持和抵抗外力的原因。土墙是坚实而牢固的，因为它的颗粒密度极高，中间的空隙非常少。

为了实现这一目标，工匠可以控制材料的颗粒度，确保空隙都被填满。即使是墙内的一个小空隙，也可能成为一个潜在的断裂点。生土材料确保了每个颗粒的均匀性和一致性。由此产生的墙体是结实的，并能在它直立时支持其自身的重量。

Ancient communities deeply understood the ways of working with earth, and have passed on traditions over generations. Builders have perfected the art of designing timeless earth structures. While methods of construction and forms of architecture vary across geographical locations, the scientific principles behind resilience are shared across borders.

Particle Stacking
A sample of raw earth can contain an assortment of shapes and sizes of minerals depending on the region it is found in. This particular matter is what makes raw earth hold well and resist external forces. An earth wall is solid and sturdy due to its extreme density of particles closely packed with as few gaps between them as possible.
To achieve this, builders control the granularity of the material, making sure that any empty space is filled. Even a small void within the wall could become a potential breaking point. In the mixture, each particle is positioned to ensure homogeneity and even consistency. The resulting configuration ensures that built walls are sturdy and can support their own weight as it stands upright.


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摩擦力

土质材料中的颗粒的粗糙度在建立坚固和有弹性的结构中起着重要作用。虽然有很大的影响，但颗粒的粗糙度和纹理只有在原子尺度上才能被注意到。当这些粗糙的表面在材料混合物中相互摩擦时，就会产生摩擦力。摩擦力阻止了可能会导致墙壁坍塌的颗粒间的相互滚动，正是这种力量使松散和干燥的颗粒得以堆积，而不会轻易散开。

Friction
The roughness of the particles in earthen material plays an important role in building robust and resilient structures. While having a large impact, the particle’s roughness and detailed texture can only be noticed at an atomic scale. When these rough surfaces rub against each other within the material mixture, friction is created. Frictional force prevents the particles from rolling away from each other, which would cause the wall to crumble down. It is this force that keeps loose and dry sand to form a conical heap rather than spreading itself flat.


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凝聚力

内聚力使颗粒之间紧密结合，这也大大影响了建筑的强度。内聚力导致颗粒之间的吸引，从而加强了摩擦力。这样的受力使得矿物颗粒保持在一起，并被塑造成各种建筑形式。内聚力确保建筑物能够承受外部力量，如拉伸和压缩应力。当可用的土壤凝聚力不够时，可以添加泥土或草等辅料来增强它。

Cohesion
Cohesive forces - the force that keeps particles closely bonded to each other - also significantly affect the strength of earth architecture. Cohesion causes attraction between material particles and thereby intensifies frictional force. The capacity of mineral particles to remain together solidifies structural members and is linked to the building’s plasticity. Cohesion ensures that the building is able to withstand external forces like tensile and compressive stress. When locally available soil is not cohesive enough, it can be enhanced with additives like topsoil or grass.


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毛细内聚力

在有水分的情况下，土的颗粒会更好地相互结合。例如，湿沙子比干沙子更有凝聚力，并能长期保持在一起。水在颗粒之间的狭窄空间里凝结，将材料混合物粘在一起。当水在混合物的表面扩散时，就会产生表面张力，将颗粒相互吸引，这种力量形式被称为毛细内聚力。

材料混合物中的毛细管内聚力程度取决于空气的相对湿度和添加到混合物中的水的量。在大气湿度存在的情况下，颗粒之间的吸引力会加强。这一特性使生土建筑能够适应不断变化的天气条件，能够抵御极端湿度的夯土墙在非常干燥的条件下会变得更加坚固。

Capillary Cohesion
In the presence of moisture, earth particles are better bound to each other. For example, wet sand is more cohesive than dry sand, and holds together for a long time. Water condenses in the narrow spaces between particles, adhering the material mixture together. As water spreads over the surface of the mixture surface tension is created, attracting the particles to each other. This form of cohesion is called capillary cohesion.
The degree of capillary cohesion in a material mixture depends on the relative humidity of the air and the amount of water added to the mix. In the presence of atmospheric humidity, the forces of attraction between particles are strengthened. This property allows earth architecture to adapt to changing weather conditions. A rammed earth wall that can resist extreme humidity will become sturdier in very dry conditions.


Image © Sam Moghadam Khamseh

生土建筑起源于世界各地的古代文明，可以作为工业建筑材料的一种可持续和经济的替代品。在这方面可以激发创新，以促进这种建筑材料的广泛使用。随着气候变化，建筑师也愈发重视这个问题，转向"新材料经济"对于建设生态可持续至关重要，生土建筑可以引领应对气候变化的道路。

With its roots in ancient civilizations across the world, earth construction is progressing as a sustainable and economic alternative to industrial building materials. The principles that guide construction can inspire innovation to propagate the widespread use of this building material. With climate change on architects’ minds, a shift to a “new materials economy” is critical in order to build ecologically sustainable environments. Earth architecture can lead the way to climate resilience.