An inverted arch or invert is a

civil engineering Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, canals, dams, airports, sewage ...

structure in the form of an inverted

arch An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it. Arches may be synonymous with vaul ...

, inverted in comparison to the usual

arch bridge An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct ...

. Like the

flying arch A flying arch is a form of arch bridge that does not carry any vertical load, but is provided solely to supply outward horizontal forces, to resist an inwards compression. They are used across cutting (transportation), cuttings, to avoid them colla ...

, the inverted arch is not used to support a load, as for a bridge, but rather to resist sideways, inwards loads. The conventional arch supports a vertical load downwards on the centre of the arch and translates this into forces both downwards and outwards at the base of the arch. In most cases, this sideways force is a nuisance and must be resisted by either strong foundations or a further 'bowstring' girder, in the form of a

tied-arch bridge A tied-arch bridge is an arch bridge in which the outward horizontal forces of the arch(es) caused by tension at the arch ends to a foundation are countered by equal tension of its own gravity plus any element of the total deck structure such grea ...

. Inverted arches are used where sideways forces must be restrained, and where space is most easily available ''beneath'' a construction. They have often been applied to

railway cutting Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in Track (rail transport), tracks. In contrast to road transport, where the ...

s, but are perhaps most distinctively used as the base of docks, particularly

dry dock A dry dock (sometimes drydock or dry-dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, ...

s and locks that must be supported even when they are empty of water that could otherwise resist the sidethrust of their walls. Some

canal tunnel {{Refimprove, date=September 2009 A canal tunnel is a tunnel for a canal. The building of a canal tunnel is crucial to help a waterway that is normally used for shipping cross a difficult section of terrain. They are also constructed to reduce th ...

s were built oval in section, such as the

Newbold-on-Avon Newbold-on-Avon (usually shortened to just Newbold) is a suburb of Rugby in Warwickshire, England, located around 1½ miles north-west of the town centre, it is adjacent to the River Avon from which the suffix is derived. Newbold was historicall ...

tunnel, where the lower section forms an invert for strength. A further use of inverted arches is to support lengthways forces from another arch, such as a bridge or viaduct. This is often done on poor ground, to reduce the ground loading otherwise and thus the need for extensive foundations. In the simplest case, the arches simply spread the downwards loads of viaduct piers into a wider ground area, exactly as for an inverted arch bridge. Such arches were used beneath the

Hownes Gill Viaduct The Hownsgill Viaduct (in some sources called Hownes Gill Viaduct and locally called the Gill bridge) is a former railway bridge located west of Consett in County Durham, England. It is currently used as a footpath and cycleway. Background From ...

, on the advice of Robert Stephenson. Inverted arches have also been added to existing bridges, to reinforce them after their banks start to slide inwards. Such a repair was applied to

The Iron Bridge The Iron Bridge is a cast iron arch bridge that crosses the River Severn in Shropshire, England. Opened in 1781, it was the first major bridge in the world to be made of cast iron. Its success inspired the widespread use of cast iron as a str ...

in the 1970s. Inverted arches are often used in conjunction with

retaining wall Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides. Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to ...

s. The arch provides a foundation for the walls and can resist the sideways forces upon them. The retaining wall also provides the vertical load needed by the arch.

References

Arches and vaults {{Architecturalelement-stub

See also

References