Sandbag
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Sandbags are mainly used in flood protection and dike defense (building sandbag dykes, raising existing dikes , securing dyke feet, erecting springs or protecting buildings ) and in the military sector. There they serve as cover against shrapnel and bullets. Compared to fixed cover, they have the advantage that there are no ricochets . Sandbag dams can also be used to catch contaminated fire fighting water. The creation of simple dwellings is possible with the help of sandbags.
Pond bags are sandbags from water- permeable ( polypropylene ) fabric, the coarse unbroken rolling gravel (grit usually 16/32) are filled and for modeling and refinement of film ponds are used.
Statics
Walls or barriers made of sandbags are basically subject to the laws of gravity walls . They can reach great heights, but should always be wider at the bottom than at the top. The greater slope should be on the side facing the water in order to use its own weight for stabilization. However, logistically it is hardly feasible to build large structures out of sandbags, even if this would be technically possible.
Sandbags and sandbag walls are less exposed to wind, waves and changing water levels on rivers than on the sea, where they are also affected by surf and tides . They are therefore less common at the sea than at rivers.
material
Sandbags are made of natural fibers (e.g. jute ) or plastic (e.g. polypropylene ). To protect against flooding, 2/3 of them are filled with sand . Sacks made of plastic have the disadvantage that they slip away more easily than natural fiber sacks. If natural fiber bags come into contact with water, they become soaked up and swell up. This also seals the sandbag dike. In addition, the natural fibers rot if sacks are left in the dike or are swept away by the river.
Plastic bags are preferable if filled bags are to be stored for a longer period of time. This is regularly the case with dike protection associations in flood-prone areas.
The bags are usually closed with tape or tie wire . They can also be sewn with special bag sewing machines. This has the advantage of a stronger lock, better shoring and safer or more effective transport. If there is not enough time to close, they can also be used openly. The opening is folded over and placed under the sack. The weight of the sand lies on the bagged material. When installing the bags, care must also be taken that there are no gaps. In order to achieve this, the lying sacks are kicked into place.
Filling
You can fill the sandbags manually or by machine with a sandbag filling machine .
Manual filling of sandbags
Improvised sandbag filling (reversed traffic cones )
Manual filling of the sandbags with a sand silo
Manual filling with conveyor belt and 10-way distributor
Roll-off container sandbag filling machine (AB-SaSaFü)
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Transport of sandbags during floods
The filled sacks can often not be transported completely to the scene by trucks , boats or helicopters . The reasons for this are soggy dykes or impassable bridges. That is why they are usually transported to the laying point via a human chain .
The helpers stand some distance apart in a zigzag line. The distance should be chosen so that the sandbags can easily be passed on without changing location. Sandbags should not be thrown as this is too strenuous in the long run and can lead to injuries if the helper who catches them is not yet ready.
Alternative systems
Rapid dike systems are offered by various providers.
Big bags (mostly 1 m³) are also used as a substitute and supplement for sandbags . These can be quickly relocated using a helicopter or wheel loader. If the dyke breaks , the gap in the dyke can be temporarily closed relatively quickly. Because of the high transport costs, these are rarely used to top up an existing dam. The high individual mass is an advantage; These large bags are used in emergency situations when it is no longer possible to lay small sandbags.
Use for house building
The German architect Gernot Minke developed, among other things, a building concept in which sandbags filled with pumice were used to build load-bearing walls. He is head of the research laboratory for experimental building at the University of Kassel .
The Iranian architect Nader Khalili developed the so-called Earthbag architecture, according to which sandbags filled with earth and other materials are primarily used to build houses in the Third World. He is the founder of the Cal Earth Institute in California , which deals with the dissemination and advancement of this technology.
Web links
Individual evidence
- ↑ a b SPON: Sandbag entrepreneur from June 4, 2013, interview with the managing director of www.sandsaecke-bs.de