Editing Trench

{{Short description|Excavated channel in ground}}
{{For|other uses of the word|Trench (disambiguation)}}
[[Image:Polyethylene gas main.jpg|thumb|right|A [[gas main]] being laid in a trench]]
A '''trench''' is a type of [[digging|excavation]] or depression in the ground that is generally deeper than it is wide (as opposed to a [[swale (landform)|swale]] or a [[bar ditch]]), and narrow compared with its length (as opposed to a simple [[hole]] or [[trapping pit|pit]]).<ref>[http://www.complianceregs.com/29cfr/1926/subP/1926-650.html Code of Federal Regulations, Title 29, Volume 8, Page 374] (Code revised as of July 1, 2003, via ''Compliance Magazine's'' website) {{webarchive|url=https://web.archive.org/web/20070602050133/http://www.complianceregs.com/29cfr/1926/subP/1926-650.html|date=June 2, 2007}}</ref> 

In [[geology]], trenches result from [[erosion]] by rivers or by geological movement of [[tectonic plates]]. In [[civil engineering]], trenches are often created to install underground [[utilities]] such as [[Pipeline transport|gas]], [[Water distribution system|water]], [[Underground power lines|power]] and [[Undergrounding|communication]] lines. In [[construction]], trenches are dug for foundations of buildings, retaining walls and dams, and for [[Tunnel construction#Cut-and-cover|cut-and-cover]] construction of tunnels. In [[archaeology]], the "trench method" is used for searching and [[Excavation (archaeology)|excavating]] ancient [[ruin]]s or to dig into [[stratum|strata]] of sedimented material. In [[geotechnical engineering]], trench investigations locate faults and investigate deep soil properties. In [[trench warfare]], soldiers occupy trenches to protect them against weapons fire and artillery. 

Trenches are dug using manual tools such as [[shovel]] and [[pickaxe]] or heavy equipment such as [[backhoe]], [[Trencher (machine)|trencher]], and [[excavator]].

For deep trenches, the instability of steep earthen walls requires engineering and safety techniques such as [[Trench shoring|shoring]]. Trenches are usually considered temporary structures that are backfilled with [[soil]] after construction or abandoned after use. Some trenches are stabilized using durable materials such as [[concrete]] to create open passages such as [[canal]] and sunken roadways.

== Geology ==
[[File:Atlantic-trench.JPG|thumb|Depiction of the [[topography]] of the [[Puerto Rico Trench]], the deepest part of the Atlantic Ocean]]

Some trenches are created as a result of [[erosion]] by running water or by [[glacier]]s (which may have long since disappeared). Others, such as [[rift valley]]s or [[oceanic trench]]es, are created by geological movement of [[list of tectonic plates|tectonic plates]]. Some oceanic trenches include the [[Mariana Trench]] and the [[Aleutian Trench]].<ref>{{Cite web|url=https://geonames.nga.mil/namesgaz/|access-date=2021-06-06|website=geonames.nga.mil|title=Geonames search}}</ref><ref>{{Cite book |url=http://archive.org/details/webstersnewgeogr00merr|title=Webster's new geographical dictionary.|date=1984|publisher=Merriam-Webster|others=Internet Archive|isbn=978-0-87779-446-2}}</ref> The former geoform is relatively deep (approximately {{convert|10|km|mi}}), linear and narrow, and is formed by [[subduction|plate subduction]] when plates converge.<ref>{{Cite web|title=Geologylink - Glossary O|url=https://college.cengage.com/geology/resources/geologylink/glossary/o.html|access-date=2021-06-06|website=college.cengage.com}}</ref>

== Civil engineering ==
{{See also|Utility tunnel}}
[[File:Trench digger, Baku (P1090226).jpg|thumb|Automated trench digging on a street in Baku]]
In the [[civil engineering]] fields of construction and maintenance of infrastructure, trenches play a major role. They are used for installation of underground infrastructure or utilities (such as [[gas main]]s, [[water main]]s, [[Undergrounding|communication]] lines and [[pipeline transport|pipelines]]) that would be obstructive or easily damaged if placed above ground. Trenches are needed later for access to these installations for service. They may be created to search for pipes and other infrastructure whose exact location is no longer known ("search trench" or "search slit"). Finally, trenches may be created as the first step of creating a [[foundation (architecture)|foundation wall]]. [[Trench shoring]] is often used in trenchworks to protect workers and stabilise the steep walls.

An alternative to digging trenches is to create a [[utility tunnel]]. Such a tunnel may be dug by [[Tunnel construction|boring]] or by using a trench for [[Tunnel construction#Cut-and-cover|cut-and-cover]] construction. The advantages of utility tunnels are the reduction of maintenance manholes, one-time relocation, and less excavation and repair, compared with separate cable ducts for each service. When they are well mapped, they also allow rapid access to all utilities without having to dig access trenches or resort to confused and often inaccurate utility maps. 

An important advantage to placing utilities underground is public safety. Underground power lines, whether in common or separate channels, prevent downed utility cables from blocking roads, thus speeding emergency access after natural disasters such as [[Earthquake|earthquakes]], hurricanes, and tsunamis.<ref>{{Cite web|title=StackPath|url=https://www.hydraulicspneumatics.com/technologies/hydraulic-pumps-motors/article/21888001/trenching-without-the-trench|access-date=2021-06-06|website=www.hydraulicspneumatics.com}}</ref>

In some cases, a large trench is dug and deliberately preserved (not filled in), often for transport purposes.  This is typically done to install depressed [[motorway]]s, open [[railway cutting]]s, or [[canal]]s. However, these large, permanent trenches are significant barriers to other forms of travel, and often become [[de facto]] boundaries between neighborhoods or other spaces.

== Military engineering ==
{{Main|Trench warfare}}

Trenches have often been dug for military purposes. In the pre-[[firearm]] era, they were mainly a type of hindrance to an attacker of a fortified location, such as the [[moat]] around a [[castle]] (this is technically called a [[ditch (fortification)|ditch]]). An early example of this can be seen in the [[Battle of the Trench]], a [[religious war]], one of the early [[List of expeditions of Muhammad|battles]] fought by [[Muhammad]].<ref name="Sa">{{Cite book |last=Sa'd |first=Ibn |url=https://books.google.com/books?id=_vnXAAAAMAAJ&q=jandal |title=Kitab al-tabaqat al-kabir |publisher=Pakistan Historical Society |year=1967 |volume=2 |pages=82–84 |asin=B0007JAWMK}}</ref>

With the advent of accurate firearms, trenches were used to shelter troops. Trench warfare and tactics evolved further in the [[Crimean War]], the [[American Civil War]] and [[World War I]], until systems of extensive main trenches, backup trenches (in case the first lines were overrun) and communication trenches often stretched dozens of kilometres along a front without interruption, and some kilometres further back from the front line. The area of land between trenches in trench warfare is known as "[[No man's land|No Man's Land]]" because it often offers no protection from enemy fire. After [[World War I|WW1]] had concluded, the trench became a symbol of [[World War I|WW1]] and its horrors.

=== Gallery ===
<gallery mode="packed" heights="150px">
File:Tuyuti1.jpg|Allied troops entrenched in the [[Battle of Tuyutí]].
File:Soldiers in trench.jpg|Soldiers in a trench during the [[Gallipoli Campaign]] of World War I.
File:Boer Trench.jpg|The [[Boer]] trench at the [[Battle of Magersfontein]] contributed to the surprise defeat of the Highland Brigade on 11 December 1899 during the [[Second Boer War]].
File:Snow at the front (4687960129).jpg|Soldiers in a trench on the Western Front in [[World War I]] in winter.
File:UA EDM4S anti-drone rifle 01.jpg|A Ukrainian soldier, equipped with an [[Directed-energy weapon#Anti-drone rifle|anti-drone gun]], in a trench during the [[2022 Russian invasion of Ukraine]].
</gallery>

== Archaeology ==
[[File:Archaeological dig, Rectory Farm, Brampton, Cambs - geograph.org.uk - 1304628.jpg|thumb|Archaeological trench on an English farm site]]
Trenches are used for searching and [[Excavation (archaeology)|excavating]] ancient [[ruin]]s or to dig into [[stratum|strata]] of sedimented material to get a sideways (layered) view of the deposits – with a hope of being able to place found objects or materials in a chronological order. The advantage of this method is that it destroys only a small part of the site (those areas where the trenches, often arranged in a grid pattern, are located). However, this method also has the disadvantage of only revealing small slices of the whole volume, and modern archeological digs usually employ [[combination methods]].<ref>{{Cite web|title=Evaluation Trial Trenching {{!}} Archaeological Services {{!}} Wessex Archaeology|url=https://www.wessexarch.co.uk/archaeological-services/evaluation-trial-trenching|access-date=2021-06-05|website=www.wessexarch.co.uk|language=en}}</ref>

== Safety ==
Trenches that are deeper than about 1.5 [[meter|m]] present safety risks arising from their steep walls and confined space. These risks are similar those from pits or any steep-walled excavations. The risks include falling, injury from [[cave-in]] (wall collapse), inability to escape the trench, drowning and [[asphyxiation]].<ref name="OSHAtrenching">{{cite web |title=eTools:Trenching and Excavation |url=https://www.osha.gov/etools/construction/trenching |publisher=Occupational Safety and Health Administration (OSHA)}}</ref><ref name="NIOSHTrenching">{{cite web |title=Trenching and Excavation |url=https://www.cdc.gov/niosh/topics/trenching/ |publisher=The National Institute for Occupational Safety and Health (NIOSH)}}</ref>
* '''Falling''' into the trench. Mitigation methods include barriers such as railings or fencing.
* '''Injury from cave-in''', meaning collapse of a steep wall. Mitigation includes construction of sloped walls (''sloped trench'') or stepped walls (''benched trench''). For vertical walls, [[trench shoring]] stabilizes the walls, and [[trench shielding]] provides a barrier against collapsed material. The risk of cave-in increases from ''surcharge load'', which is any weight placed outside the trench near its edge. These loads include the ''spoil pile'' (soil excavated from the trench) or heavy equipment. These add extra stress to the walls of the trench.
* '''Inability to escape''' the trench because of steep and unstable walls, which may be difficult to climb. Ladders, stairs, or ramps allow exit. [[Crane (machine)|Cranes]] may assist rescue. 
* '''Drowning''' in water or mud that has accumulated in the trench from rain, seepage, or leaking water pipes.
* '''Asphyxiation, poisoning, fire and explosion''' from gasses that are denser than air that have settled in a trench. These may come from nearby industrial processing of these gasses, intentional use within the trench, or leakage from nearby plumbing. These present an [[asphyxiation]] hazard and may also be toxic. Burnable gasses such as [[natural gas]] present a fire and explosion risk. Oxidizers such as pure oxygen increase the risk of fire from other fuels present in the trench. Gasses such as pure [[nitrogen]] and [[natural gas]] have densities similar to pure air but are denser when cold, for example when they have evaporated from liquid form, and may creep along the ground and fill the trench. Ventilation fans and [[Duct (flow)|ducts]] reduce the risk. [[Oxygen]] sensors and other gas sensors detect the danger; alarms from the sensors can warn the occupants.

== See also ==
{{div col}}
* [[Abyssal plain]]
* [[Cut (earthmoving)]]
* [[Cut and fill]]
* [[Ditch]]
* [[Gully]]
* [[Sunken lane#Erosion]]
* [[Trench (album)|''Trench'' (album)]]
* [[Trench coat]]
* [[Trench fever]]
* [[Trench foot]]
* [[Trench mouth]]
* [[Trench warfare]]
* [[Tunnel]]
* [[Tunnel warfare]]
* [[Underground city]]
* [[Underground living]]
* [[Utility tunnel]]
{{div col end}}

== References ==
{{Reflist}}

== External links ==
{{Commons category}}
{{Wiktionary}}
* [https://www.cdc.gov/niosh/topics/trenching/ Trenching and Excavation] (a [[NIOSH]] Safety and Health Topic, [[Centers for Disease Control and Prevention]])
* [https://www.cdc.gov/niosh/docs/2006-133D/ Trench Safety Awareness] (a [[NIOSH]] Publication, [[Centers for Disease Control and Prevention]])

{{Geotechnical engineering|state=collapsed}}
{{Authority control}}

[[Category:Cuts (earthmoving)|*]]
[[Category:Earth structures]]