Sandbag

Asandbagordirtbagis a bag or sack made ofhessian (burlap),polypropyleneor other sturdy materials that is filled withsandorsoiland used for such purposes asflood control,militaryfortificationin trenches and bunkers, shielding glass windows in war zones,ballast,counterweight,and in other applications requiring mobile fortification, such as adding improvised additional protection to armored vehicles or tanks.

The advantages are that the bags and sand are inexpensive. When empty, the bags are compact and lightweight for easy storage and transportation. They can be brought to a site empty and filled with local sand or soil. Disadvantages are that filling bags is labor-intensive. Without proper training, sandbag walls can be constructed improperly causing them to fail at a lower height than expected, when used in flood-control purposes. They can degrade prematurely in the sun and elements once deployed. They can also become contaminated by sewage in flood waters making them difficult to deal with after flood waters recede.^[1]In a military context, improvised up-armouring of tanks or armored personnel carriers with sandbags is not effective against cannons (though it may offer protection against somesmall arms).

Sandbags have traditionally been filled manually usingshovels.Since the 1990s, machine filling has become more common, allowing the work to be done more quickly and efficiently.

Usage

Troops from theGrenadier Guardsconstructing sandbag defenses around government buildings inBirdcage Walk,London, May 1940.

Flood control

Properly stacked sandbags^[2]are an effective deterrent against damagingfloodwaters. Sandbags can be used to buildlevees,barricades,dikesandbermsto limit erosion from flooding. Sandbags can also be used to fortify existing flood control structures and limit the effects ofsand boils.Sandbag structures do not prevent water seepage and therefore should be built with the central purpose of diverting flood water around or away from buildings.

Properly filled sandbags for flood control are filled one-half to two-thirds full with clean washed sand. In an emergency, if clean sand is in limited supply, gravel or dirt can also be used with less effective end results. When filled sandbags are stacked or laid in place, the contents need to settle flat to the ground. Sandbags filled over two-thirds full will not form an adequate seal to the ground or structure. Likewise sandbags filled under one-half will generally also form an inadequate seal to the ground when placed.

The best practices for filling sandbags require a three-person team. One team member will crouch down and hold open the bag to form a collar opening. The second team member places the tip of a pointed shovel with sand into the opened sandbag. A square shovel is not recommended as the blade of the shovel will not fit into the sandbag when filling. The third team member will transport and stockpile the filled sandbags.

Properly placed sandbags will be set lengthwise and parallel to the water flow with the folded or open end of the sandbag facing upstream. All loose debris should be removed from the placement surface and the lowest areas are the first spots to be filled in with sandbags. Each bag must be set consecutively with the tightly packed bottom slightly overlapping the previously placed sandbag. Subsequent layers of bags should be offset by 1/2 the length of a sandbag to eliminate voids and improve the wall seal. Each placed bag should be tamped and flattened to improve the seal.

The two primary methods for stacking sandbags to build flood control structures are the (1) Single Stack placement, and; (2) Pyramid Placement Method.^[3]

Fortification

The military uses sandbags for fieldfortificationsand as a temporary measure to protect civilian structures. Because burlap and sand are inexpensive, large protective barriers can be erected cheaply. The friction created by moving soil or sand grains and tiny air gaps makes sandbags an efficientdissipatorofexplosive blast.^[4]The most common sizes for sandbags are 14 by 26 inches (36 by 66 cm) to 17 by 32 inches (43 by 81 cm).^[5]^[6]These dimensions, and the weight of sand a bag this size can hold, allow for the construction of an interlocking wall likebrickwork.

Individual filled bags are not too heavy to lift and move into place. They may be laid in excavated defences asrevetment,or as free-standing walls above ground where excavations are impractical. As plain burlap sandbags deteriorate fairly quickly, sandbag structures meant to remain in place for a long time may be painted with aportland cement slurryto reduce the effects ofrotand abrasion. Cotton ducking sandbags last considerably longer than burlap and are hence preferable for long-term use. However, the vast majority of sandbags used by modern military and for flood prevention are made of circular wovenpolypropylene.Some of the World War I memorial trenches were rebuilt with concrete sandbags after the First World War—although criticized as looking unnatural, they have lasted well. During World War II in Great Britain, some aircraft revetments and pillboxes were made from concrete filled sandbags, again these have lasted well.

Sandbag fortifications have been used since at least the late 16th century. For example, the rebelliousMughalgovernorMirza Jani Begused improvised sandbags made out of boat sails to construct a makeshift fort atUnarpur,Sindh,in 1592.^[7]Later, British loyalists used sandbag and log fortifications in the 1781Siege of Ninety-Sixduring theAmerican Revolutionary War.Nathanael Greenewas familiar enough with the fortification technique to equip his troops with hooks to pull down the sandbag and log walls when they stormed the StarRedoubtinNinety Six, South Carolina.^[8]

In ancient times, temporary sandbag forts known as an antestature were made out of sandbags.They were historically hastily established by a retreating force to slow the progress of the enemy. The word comes from theLatinante( "before" ), andstatūra( "a standing" ).^[9]

Bulk bags

Plastic geotextile bags

Bulk bags,also known as big bags, are much larger than traditional sandbags. Moving a bag of this size typically requires aforklift truck.Bulk bags are usually made of woven or non-wovengeotextiles.

Large bags of sand are often used in flood control and making temporary patches to water barriers. For example, Thailand utilized bulk bags filled with sand to erect temporary walls to protect against the2011 Thailand floods.

Other uses

Sandbags being filled using a ladder on sawhorses withtraffic conesaschutesorfunnels,Moorhead, Minnesota,2009.

Sandbags are also used for disposable ballast ingas balloons,and ascounterweightsfortheatre sets.Some temporary construction signs or advertising signs are held in place and secured against being blown over with sandbags.

DuringWorld War II,sandbags were also used as extemporized "soft armor" on American tanks, with the goal of protecting the tanks from German anti-tank rounds,^[10]but they were largely ineffective.

Sandbags can also be carried within vehicles to provide improved traction during inclement weather (typically stored above the drive wheels where the increased weight improves traction). If ever stuck, sand can be removed and placed directly onto the slippery surface thereby providing greatly improved traction. Sandbags are also used by off-road enthusiasts instead of sand plates or sand ladders to assist the vehicle to get traction and momentum after being stuck in soft sand. The same sandbags can be used to bridge deep holes or ditches. Apart from being very light and taking very little space (when empty), the sandbags are a much cheaper option than any of the other options (sand plates, sand ladders, multipurpose bags, etc.).

Sandbags are often used to temporarily stabilize soil from erosion, such as oceanfront structures whose foundations have been undermined by heavy waves. Sandbags are also used inearthbag constructionto make inexpensive, environmentallysustainablehomes. In addition, sandbags are often used when shooting a long gun, specifically a rifle or sniper rifle, from a rest, as it provides support for the weapon, allowing for less movement during shooting.^{[citation needed]}

Sandbags of various sizes and weights can be used for exercise orresistance training.^[11]

Sandbags are used for safety in film, video and theatrical production. Sandbags are often used as easily portable weight to lower the center of gravity of a Light stand or a C-Stand where heavy items are placed at the top of a high stand often having a small base. Shot bags are another type of flexible weight used for the same purpose.

Gallery

Manual filling of sandbags.
Improvised method of sandbag filling.
Sandbags being filled using improvised methods, lumber andtraffic conesaschutes,Iowa City, Iowa,2008.
Manual filling of sandbags from a hopper orsilo
Manual filling with aconveyor beltand a 12 direction sandbag filler called "The Sandbagger" capable of filling over 5,000 sandbags an hour.^[12]
Filling multiple sandbags with afront-end loader.
A German,roller containermounted, sandbag filling machine
An Afghan Local Police officer carries a bundle of empty sandbags during a checkpoint construction project
A sandbag levee in North Dakota
A sandbag wall to limit erosion, wave damage and flooding
Sandbag operation at Venice Beach pier in California. September 30, 2010.
AFirst Balkan WarBulgarian foxhole
Adefensive fighting positionmade with sandbags
Sandbagged aircraftrevetment
World War II aircraft revetments made of concrete filled sandbags, as seen decades later in 2009.