FootbridgeA footbridge (also a pedestrian bridge, pedestrian overpass, or pedestrian overcrossing) is a bridge designed solely for pedestrians. While the primary meaning for a bridge is a structure which links "two points at a height above the ground", a footbridge can also be a lower structure, such as a boardwalk, that enables pedestrians to cross wet, fragile, or marshy land. Bridges range from stepping stones–possibly the earliest man-made structure to "bridge" water–to elaborate steel structures.
Double-track railwayA double-track railway usually involves running one track in each direction, compared to a single-track railway where trains in both directions share the same track. In the earliest days of railways in the United Kingdom, most lines were built as double-track because of the difficulty of co-ordinating operations before the invention of the telegraph. The lines also tended to be busy enough to be beyond the capacity of a single track. In the early days the Board of Trade did not consider any single-track railway line to be complete.
Holland TunnelThe Holland Tunnel is a vehicular tunnel under the Hudson River that connects Hudson Square and Lower Manhattan in New York City in the east to Jersey City, New Jersey in the west. The tunnel is operated by the Port Authority of New York and New Jersey and carries Interstate 78. The New Jersey side of the tunnel is the eastern terminus of NJ Route 139. The Holland Tunnel is one of three vehicular crossings between Manhattan and New Jersey; the two others are the Lincoln Tunnel and George Washington Bridge.
Paris MétroThe Paris Métro (Métro de Paris metʁo də paʁi; short for Métropolitain metʁɔpɔlitɛ̃) and operated by the Régie autonome des transports parisiens (RATP) is a rapid transit system in the Paris metropolitan area, France. A symbol of the city, it is known for its density within the capital's territorial limits, uniform architecture and unique entrances influenced by Art Nouveau. The system is long, mostly underground. It has 308 stations of which 64 have transfers between lines.
Simplon TunnelThe Simplon Tunnel (Simplontunnel, Traforo del Sempione or Galleria del Sempione) is a railway tunnel on the Simplon railway that connects Brig, Switzerland and Domodossola, Italy, through the Alps, providing a shortcut under the Simplon Pass route. It is straight except for short curves at either end. It consists of two single-track tunnels built nearly 15 years apart. The first to be opened is long; the second is long, making it the longest railway tunnel in the world for most of the twentieth century, from 1906 until 1982, when the Daishimizu Tunnel opened.
Structure gaugeA structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of platforms, tunnels and bridges, and the width of the doors that allow access to a warehouse from a rail siding. Specifications may include the minimum distance from rail vehicles to railway platforms, buildings, electrical equipment boxes, signal equipment, third rails or supports for overhead lines.
Tunnel warfareTunnel warfare involves war being conducted in tunnels and other underground cavities. It often includes the construction of underground facilities (mining or undermining) in order to attack or defend, and the use of existing natural caves and artificial underground facilities for military purposes. Tunnels can be used to undermine fortifications and slip into enemy territory for a surprise attack, while it can strengthen a defense by creating the possibility of ambush, counterattack and the ability to transfer troops from one portion of the battleground to another unseen and protected.
MegaprojectA megaproject is an extremely large-scale investment project. According to the Oxford Handbook of Megaproject Management, "Megaprojects are large-scale, complex ventures that typically cost 1billionormore,takemanyyearstodevelopandbuild,involvemultiplepublicandprivatestakeholders,aretransformational,andimpactmillionsofpeople".However,1 billion is not a constraint in defining megaprojects; in some contexts a relative approach is needed, such as in developing countries, where a much smaller project (such as one with a $100 million budget) could constitute a megaproject. ShotcreteShotcrete, gunite ('gVnait), or sprayed concrete is concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface. This construction technique was invented by Carl Akeley and first used in 1907. The concrete is typically reinforced by conventional steel rods, steel mesh, or fibers. The concrete or mortar is formulated to be sticky and resist flowing when at rest to allow use on walls and ceilings, but exhibit sufficient shear thinning to be easily pumpable through hoses.
Cut and fillIn earthmoving, cut and fill is the process of constructing a railway, road or canal whereby the amount of material from cuts roughly matches the amount of fill needed to make nearby embankments to minimize the amount of construction labor. Cut sections of roadway or rail are areas where the roadway has a lower elevation than the surrounding terrain. Fill sections are elevated sections of a roadway or trackbed. Cut and fill takes material from cut excavations and uses this to make fill sections.
