Difference between revisions of "Foundation"
(→Piles) |
|||
| Line 14: | Line 14: | ||
The dust in the atmosphere is a tiny fraction of the mass of the gas and exerts negligible pressure on the buildings even in the strongest winds. However high velocity dust might scratch windows and damages surface finishes. | The dust in the atmosphere is a tiny fraction of the mass of the gas and exerts negligible pressure on the buildings even in the strongest winds. However high velocity dust might scratch windows and damages surface finishes. | ||
===Extensive Permafrost=== | ===Extensive Permafrost=== | ||
| − | It has been suggested that much of the surface is a sort of permafrost. Heat generated by structures could cause the [[water]] or [[carbon dioxide]] in the permafrost to sublimate, resulting in settling of the ground. Any [[settlement]] on this type of ground will need to take measures to protect against this possibility. The loss of CO2 or of water in the | + | It has been suggested that much of the surface is a sort of permafrost. Heat generated by structures could cause the [[water]] or [[carbon dioxide]] in the permafrost to sublimate, resulting in settling of the ground. Any [[settlement]] on this type of ground will need to take measures to protect against this possibility. The loss of CO2 or of water in the ground changes the load bearing capacity of the ground. Permafrost on Mars would be different from permafrost on earth as the frozen material is regolith, and not soil. It is unlikely to be as fluid as melted permafrost and should maintain a fair amount of load bearing capacity. |
| + | |||
| + | === No soil === | ||
| + | There is no plant life on Mars, therefore there is no soil. The material on the martian surface is either sand, rock or [[regolith]]. Soil has very low load bearing capacity and is generally removed for construction. This would not be an issue on Mars. | ||
===Internal pressure=== | ===Internal pressure=== | ||
| Line 27: | Line 30: | ||
===Piles=== | ===Piles=== | ||
| − | Piles can operate as friction elements spreading the load vertically through regolith with low load bearing capacity. | + | Piles can operate as friction elements spreading the load vertically through regolith with low load bearing capacity. Or they can extend down to stable bedrock. Piles reduce the heat transfer to the ground and can be cooled to prevent the melting of permafrost. |
===Footings=== | ===Footings=== | ||
| − | A footing is a partial slab under a wall | + | A footing is a partial slab under a wall or a column. It reduces the load on the regolith to a safe level below the load bearing capacity of the material. |
===Slab=== | ===Slab=== | ||
| − | A slab is a foundation that extends under the entirety of a building, creating a floor and reducing the ground load to the lowest level possible. Slabs on Earth are mostly under compression, however a slab on Mars might serve as part of a pressure vessel and then would be under tension. In such a case it would need to be reinforced with steel bars or other tension resistant materials | + | A slab is a foundation that extends under the entirety of a building, creating a floor and reducing the ground load to the lowest level possible. Slabs on Earth are mostly under compression, however a slab on Mars might serve as part of a pressure vessel and then would be under tension. In such a case it would need to be reinforced with steel bars or other tension resistant materials. Slabs might have high heat transfer to the surrounding ground and might need to be insulated, or actively cooled in permafrost type soils. |
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | == | + | ==Load bearing capacity of martian surface materials== |
| + | Large areas of Mars appear to be covered with lava flows and rock. The foundations on such materials would be minimal. As there is no water and no soil on Mars, most surface materials should have a high load bearing capacity. Areas with large amounts of water in the regolith might need to be protected from the heat of the settlement to maintain their load bearing capacity. | ||
| − | + | Ice is a plastic material that might flow very slowly under pressure. Tunnels dug in ice in the american Camp Century base in Greenland, [[w:Project_Iceworm|Project Iceworm]], closed surprisingly quickly . | |
| − | |||
[[Category: Construction, Assembly, Maintenance]] | [[Category: Construction, Assembly, Maintenance]] | ||
Revision as of 11:18, 11 May 2019
Any permanent or semi-permanent structure on the surface of Mars will need some type of foundation. A foundation anchors a structure to the ground, preferably to the bedrock. This stabilizes the structure against the affects of gravity, wind, and ground movements due to changes in ground moisture (water and carbon dioxide ice).
Alternatively, many foundations are of the floating type. This means that after testing the soil, the load bearing capacity is determined and the foundation is built in order to spread the load to less than the load bearing capacity of the soil. That is the main purpose of footings under house walls, for example. In a sense, all building that are not supported directly on the bedrock 'float' on the soil.
Contents
Unique Martian Considerations
The environment of Mars presents certain unique factors for foundation design.
Reduced Gravity
The lower gravity means that Martian foundations need not be as strong or thick as terrestrial counterparts.
Low Air Pressure
Low air pressure means that the Martian winds have a greatly reduced effect upon structures compared to terrestrial winds of the same speeds.
The martian atmosphere has a density of about 2% the one of Earth. As the energy from wind transmitted to a structure is a equation in the form of E=1/2mV2, it is directly proportional to the mass of the atmosphere. So for the same wind velocity the force, and consequently the pressure, will be 50 times less.
The dust in the atmosphere is a tiny fraction of the mass of the gas and exerts negligible pressure on the buildings even in the strongest winds. However high velocity dust might scratch windows and damages surface finishes.
Extensive Permafrost
It has been suggested that much of the surface is a sort of permafrost. Heat generated by structures could cause the water or carbon dioxide in the permafrost to sublimate, resulting in settling of the ground. Any settlement on this type of ground will need to take measures to protect against this possibility. The loss of CO2 or of water in the ground changes the load bearing capacity of the ground. Permafrost on Mars would be different from permafrost on earth as the frozen material is regolith, and not soil. It is unlikely to be as fluid as melted permafrost and should maintain a fair amount of load bearing capacity.
No soil
There is no plant life on Mars, therefore there is no soil. The material on the martian surface is either sand, rock or regolith. Soil has very low load bearing capacity and is generally removed for construction. This would not be an issue on Mars.
Internal pressure
A unique characteristic of martian construction is that the pressure inside the building is very high compared to the pressure outside. The pressure is about 10 tonnes per meter square of wall or floor surface. So a standard 1000 square foot (100 m2) house on Mars would exert 1000 tonnes of force onto its foundations. A large dome, as often illustrated in images of martian settlements will do the same, so a 1000 foot (300m) dome would exert 1502 x pi x 10 = 700 000 tonnes of force.
This is why martian structures are more likely to be pressure vessels, spheres and cylinders with rounded ends, rather than domes or rectangular constructions.
Types of Foundations
| This section of the article is incomplete or needs more detail. You can help Marspedia by expanding or correcting it. |
Pressurized habitats and unpressurized constructions can have different needs as far as foundations go.
Piles
Piles can operate as friction elements spreading the load vertically through regolith with low load bearing capacity. Or they can extend down to stable bedrock. Piles reduce the heat transfer to the ground and can be cooled to prevent the melting of permafrost.
Footings
A footing is a partial slab under a wall or a column. It reduces the load on the regolith to a safe level below the load bearing capacity of the material.
Slab
A slab is a foundation that extends under the entirety of a building, creating a floor and reducing the ground load to the lowest level possible. Slabs on Earth are mostly under compression, however a slab on Mars might serve as part of a pressure vessel and then would be under tension. In such a case it would need to be reinforced with steel bars or other tension resistant materials. Slabs might have high heat transfer to the surrounding ground and might need to be insulated, or actively cooled in permafrost type soils.
Load bearing capacity of martian surface materials
Large areas of Mars appear to be covered with lava flows and rock. The foundations on such materials would be minimal. As there is no water and no soil on Mars, most surface materials should have a high load bearing capacity. Areas with large amounts of water in the regolith might need to be protected from the heat of the settlement to maintain their load bearing capacity.
Ice is a plastic material that might flow very slowly under pressure. Tunnels dug in ice in the american Camp Century base in Greenland, Project Iceworm, closed surprisingly quickly .
