Editing Slurry wall

{{Short description|Civil engineering technique}}
{{More citations needed|date=September 2009}}
[[File:World Trade Center Slurry Wall, Eric Ascalon, 9-4-02.jpg|thumb|Exposed slurry wall of the [[World Trade Center (1973–2001)|World Trade Center]] at [[World Trade Center site|Ground Zero]]]]
A '''slurry wall''' is a [[civil engineering]] technique used to build [[reinforced concrete]] walls in areas of soft earth close to open water, or with a high [[groundwater]] table.<ref name=GwSlurryWall1994>
{{cite news| url = http://www.cee.vt.edu/ewr/environmental/teach/gwprimer/slurry/slurry.html| title = Slurry Walls| publisher = [[Virginia Tech]]| year = 1994| access-date = 2012-01-05| author = Gutberle|url-status = dead| archive-url = https://web.archive.org/web/20070824031544/http://www.cee.vt.edu/ewr/environmental/teach/gwprimer/slurry/slurry.html| archive-date = 2007-08-24}}</ref> This technique is typically used to build diaphragm (water-blocking) walls surrounding [[tunnel]]s and open cuts, and to lay [[foundation (engineering)|foundations]]. Slurry walls are used at [[Superfund]] sites to contain the waste or contamination and reduce potential future migration of waste constituents, often with other waste treatment methods. Slurry walls are a "well-established" technology but the decision to use slurry walls for a certain project requires geophysical and other engineering studies to develop a plan appropriate for the needs of that specific location. Slurry walls may need to be used in conjunction with other methods to meet project objectives.<ref>{{cite web |url=https://nepis.epa.gov/Exe/ZyNET.exe/10002DPY.TXT?ZyActionD=ZyDocument&Client=EPA&Index=1991+Thru+1994&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5Czyfiles%5CIndex%20Data%5C91thru94%5CTxt%5C00000003%5C10002DPY.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1&SeekPage=x&ZyPURL# |website=United States EPA |title=Engineering Bulletin: Slurry Walls}}</ref>

==Construction==
[[File:Ausführung-Schlitzwand.png|thumb|Sequence of constructing a slurry wall]]
While a trench is being excavated to create a form for a wall, it is simultaneously filled with [[slurry]] (usually a mixture of [[bentonite]] and water).  The dense but liquid slurry prevents the trench from collapsing by providing outward pressure, which balances the inward hydraulic forces and also retards water flow into the trench. The density of the slurry mix must be carefully monitored and adjusted to produce the correct outward pressure to prevent the trench walls from collapsing.

Slurry walls are typically constructed by starting with a set of concrete guide walls, typically {{convert|1|m}} deep and {{convert|0.5|m}} thick. The guide walls are constructed near the ground surface to outline the desired slurry trench, and to guide the excavation machinery. Excavation is done using a special clamshell-shaped [[excavator|digger]] or a [[hydromill trench cutter]], suspended from a crane. The excavator digs down to design depth (or bedrock) for the first wall segment.  The excavator is then lifted and moved along the trench guide walls to continue the trench with successive cuts as needed.  The trench is at all times kept filled with slurry to prevent its collapse, but the fluid filling allows the excavation machinery and excavation spoil to be moved without hindrance.

Once a particular depth of trench is reached, a [[rebar|reinforcing cage]] is lowered into the slurry-filled pit and the pit is filled with [[concrete]] from the bottom up using [[tremie]] pipes. The heavier concrete displaces the bentonite slurry, which is pumped out, filtered, and stored in tanks for use in the next wall segment, or it is recycled.

Slurry walls are successively extended to enclose an area, blocking water and softened earth from flowing into it.  Once the concrete has hardened, excavation within the now concrete-wall-enclosed area can proceed. To prevent the concrete wall from collapsing into the newly excavated area, temporary supports such as [[Tieback (geotechnical)|tieback]]s or internal crossbeams are installed. When completed, the structure built within the walled-off area usually supports the wall, so that tiebacks or other temporary bracing may be optionally removed.

==History==
The slurry wall technique was first introduced in the 1950s during the excavations of the [[Milan Metro Line 1|Red Line]] of the [[Milan Metro]] in Italy by the company ICOS (Impresa Costruzioni Opere Specializzate). This new technology became an important component of the top-down tunnelling method also known as ''Metodo Milano'' ("Milan method").<ref>{{Cite web|title = Primo by Ex Libris -|url = http://www.primo.polimi.it/primo_library/libweb/action/dlDisplay.do?vid=base&afterPDS=true&docId=|access-date = 2015-08-25}}</ref>

Slurry wall construction was used in 1967–1968 to construct the [[the Bathtub|"bathtub"]] that surrounded the foundations of most of the [[World Trade Center site]] in New York City.<ref>{{cite news |title= Looking to a Wall That Limited the World Trade Center’s Devastation|author=  David W. Dunlap|url= https://www.nytimes.com/2013/09/12/nyregion/looking-to-a-wall-that-limited-the-world-trade-centers-devastation.html|newspaper= [[New York Times]]|date=  September 11, 2013 |access-date=  September 11, 2013 | quote = A portion of the slurry wall was deliberately left exposed in the Foundation Hall of the National September 11 Memorial Museum, set to open next year. }}</ref> In the 1980s, the [[Red Line Northwest Extension]] project in Boston was one of the first projects in the US to use the modern form of the technology, with hydromill trench cutters and the "Milan method". Slurry walls were also used extensively in Boston's 1990s [[Big Dig]] tunnel project.

==Design==
The design of a slurry wall (diaphragm wall) includes the design of wall thickness and reinforcements. Thickness of a slurry wall in preliminary design is generally set to about 4-8% of the excavation depth. Slurry wall design is undertaken based on [[bending moment]]  and [[Shearing (physics)|shear]] envelope obtained from the [[stress analysis]]. In the design of such underground walls, width of the unit is considered as one meter, and the wall is analyzed under [[plane strain]] condition. Since the length-to-width ratio of excavations is generally large, plane strain conditions can be assumed.<ref name="Bahrami">{{cite journal |last1=Bahrami |first1=M. |last2=Khodakarami |first2=M.I.  |last3=Haddad |first3=A.|title=Seismic behavior and design of strutted diaphragm walls in sand|journal=Computers and Geotechnics |date=April 2019 |volume=108 |pages=75–87 | doi= 10.1016/j.compgeo.2018.12.019}}</ref>

In a single-phase diaphragm wall, also known as a "cut-off wall", a binder (usually cement) is added to the supporting fluid so that the supporting fluid hardens without exchange.<ref>{{Citation |title=(Ab)Dicht(ungs)(schlitz)wand f |date=2013 |url=http://dx.doi.org/10.1007/978-3-642-33335-4_10282 |work=Wörterbuch GeoTechnik/Dictionary Geotechnical Engineering |pages=7–7 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |access-date=2022-03-28}}</ref> One application for this type of construction is a [[landfill]] seal that is to be retrofitted later.

==Gallery==
{{gallery|mode=packed
|File:Slurry Wall Hydromill In Tel Aviv.jpg|[[Hydromill trench cutter]]
|File:SlurrywallEquipment.jpg|Clamshell-type slurry wall excavator
|File:Muros guia muros pantalla aparcamiento.JPG|A set of slurry wall guide walls before excavation
}}

==See also==
* [[Retaining wall]]
* [[Building of the World Trade Center]]
* [[Grout curtain]]

==References==
<references/>

==External links==
{{Commons category}}
*[https://www.youtube.com/watch?v=0rl1DNduT2w Video Overview of Slurry Wall Construction]

{{Geotechnical engineering|state=collapsed}}

{{Authority control}}

[[Category:Geotechnical shoring structures]]
[[Category:Types of wall]]