A convoy is a group of vehicles , typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support and can help maintain cohesion within a unit. It may also be used in a non-military sense, for example when driving through remote areas.
103-580: The Eisenhower Tunnel , officially the Eisenhower–Edwin C. Johnson Memorial Tunnel , is a dual-bore, four-lane vehicular tunnel in the western United States , approximately 60 miles (97 km) west of Denver , Colorado. The tunnel carries Interstate 70 (I-70) under the Continental Divide in the Rocky Mountains . With a maximum elevation of 11,158 feet (3,401 m) above sea level , it
206-497: A mining background, expressed a common superstition that a woman brought bad luck to a mine. One worker insisted, "It's a jinx. I've seen too many die after a woman was in the tunnel." Bonnema sued the department for the right to work inside the tunnel. She countered she was in better shape and more agile than most of the men who were working on the tunnel. Emboldened by the passage of an equal rights law in Colorado, she finally entered
309-660: A rapid transit network are usually in the tunnel. Some tunnels are used as sewers or aqueducts to supply water for consumption or for hydroelectric stations. Utility tunnels are used for routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment. Secret tunnels are built for military purposes, or by civilians for smuggling of weapons , contraband , or people . Special tunnels, such as wildlife crossings , are built to allow wildlife to cross human-made barriers safely. Tunnels can be connected together in tunnel networks . A tunnel
412-422: A convoy, its "footprint" (the area within which it could be spotted) was far smaller than if the individual ships had traveled independently. In other words, a submarine had less chance of finding a single convoy than if it were scattered as single ships. Moreover, once an attack had been made, the submarine would need to regain an attack position on the convoy. If, however, an attack were thwarted by escorts, even if
515-694: A handful of ships before the rest managed to escape, and a small escort of warships could easily thwart it. As a result of the convoy system's effectiveness, wartime insurance premiums were consistently lower for ships that sailed in convoys. Many naval battles in the Age of Sail were fought around convoys, including: By the end of the Napoleonic Wars , the Royal Navy had in place a sophisticated convoy system to protect merchant ships. Losses of ships travelling out of convoy, however, were so high that no merchant ship
618-459: A highway, convoys are also useful to conserve fuel by drafting . The film Convoy , inspired by a 1975 song of the same name , explores the camaraderie between truck drivers , where the culture of the CB radio encourages truck drivers to travel in convoys. Truck convoys are sometimes organized for fundraising , charity , or promotional purposes. They can also be used as a form of protest , such as
721-449: A large factor in the decision making process. Civil engineers usually use project management techniques for developing a major structure. Understanding the amount of time the project requires, and the amount of labor and materials needed is a crucial part of project planning. The project duration must be identified using a work breakdown structure and critical path method . Also, the land needed for excavation and construction staging, and
824-461: A pipe jack, with the span of some box jacks in excess of 20 metres (66 ft). A cutting head is normally used at the front of the box being jacked, and spoil removal is normally by excavator from within the box. Recent developments of the Jacked Arch and Jacked deck have enabled longer and larger structures to be installed to close accuracy. There are also several approaches to underwater tunnels,
927-702: A position as an engineering technician with the Colorado Department of Transportation she was given an assignment on the Straight Creek Tunnels project. Her supervisor misread her resume and thought that he was hiring "James." When the supervisor discovered that the department had hired a woman, she was tasked with doing support work from the office. There was opposition to a woman entering the construction site. One supervisor stated that if she entered, "Those workers would flat walk out of that there tunnel and they'd never come back." The workers, most of whom had
1030-499: A result, the Japanese merchant fleet was largely destroyed by the end of the war. Japanese submarines, unlike their U.S. and German equivalents, focused on U.S. battle fleets rather than merchant convoys, and while they did manage some early successes, sinking two U.S. carriers, they failed to significantly inhibit the invasion convoys carrying troops and equipment in support of the U.S. island-hopping campaign. Several notable battles in
1133-421: A specialized method called clay-kicking for digging tunnels in clay-based soils. The clay-kicker lies on a plank at a 45-degree angle away from the working face and rather than a mattock with his hands, inserts with his feet a tool with a cup-like rounded end, then turns the tool with his hands to extract a section of soil, which is then placed on the waste extract. Clay-kicking is a specialized method developed in
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#17328444830591236-506: A tiny proportion of the ocean in sight, without intelligence or radar, warships and even aircraft would be fortunate in coming across a submarine. The Royal Navy and later the United States Navy each took time to learn this lesson. Conversely, a U-boat's radius of vision was even smaller and had to be supplemented by regular long-range reconnaissance flights. For both major allied navies, it had been difficult to grasp that, however large
1339-434: A tube can be sunk into a body of water, which is called an immersed tunnel. Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support system strong enough to carry the load of what is to be built above the tunnel. There are two basic forms of cut-and-cover tunnelling: Shallow tunnels are often of the cut-and-cover type (if under water, of
1442-710: A tunnel than a sufficiently strong bridge). Some water crossings are a mixture of bridges and tunnels, such as the Denmark to Sweden link and the Chesapeake Bay Bridge-Tunnel in Virginia . There are particular hazards with tunnels, especially from vehicle fires when combustion gases can asphyxiate users, as happened at the Gotthard Road Tunnel in Switzerland in 2001. One of the worst railway disasters ever,
1545-432: A tunnel. Bridges usually require a larger footprint on each shore than tunnels. In areas with expensive real estate, such as Manhattan and urban Hong Kong , this is a strong factor in favor of a tunnel. Boston's Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, reclaim land, redecorate, and reunite the city with the waterfront. The 1934 Queensway Tunnel under
1648-509: Is 1.693 miles (2.72 km) long, while the Edwin C. Johnson Memorial Bore (eastbound tunnel) is 1.697 miles (2.73 km) long. The tunnels are sloped with a 1.64% grade , with an elevation of 11,013 feet (3,357 m) at the east portal and 11,158 feet (3,401 m) at the west portal. At its dedication, the Eisenhower Tunnel was the highest vehicular tunnel in the world. While it remains
1751-418: Is allowed in this tunnel tube, and motorcyclists are directed to the other tube. Each level was built with a three-lane roadway, but only two lanes per level are used – the third serves as a hard shoulder within the tunnel. The A86 Duplex is Europe's longest double-deck tunnel. Convoy Naval convoys have been in use for centuries, with examples of merchant ships traveling under naval protection dating to
1854-461: Is closed—such as for construction or storms—the hazmat prohibition is temporarily lifted and the tunnel is closed to regular traffic once per hour to allow hazmats to be escorted through the tunnel in a convoy . The idea for a tunnel under Loveland Pass existed since at least the 1950s. William A.H. Loveland had an idea of a tunnel under the divide in 1867, but instead got the wagon road now known as Loveland Pass built. Serious discussion began when
1957-500: Is intended to carry both the Istanbul metro and a two-level highway, over a length of 6.5 km (4.0 miles). The French A86 Duplex Tunnel [ fr ] in west Paris consists of two bored tunnel tubes, the eastern one of which has two levels for light motorized vehicles, over a length of 10 km (6.2 miles). Although each level offers a physical height of 2.54 m (8.3 ft), only traffic up to 2 m (6.6 ft) tall
2060-648: Is one of the highest vehicular tunnels in the world. The tunnel is the longest mountain tunnel and highest point on the Interstate Highway System . Opened in 1973, the westbound bore is named after Dwight D. Eisenhower , the U.S. President for whom the Interstate system is also named. The eastbound bore was completed in 1979 and is named for Edwin C. Johnson , a Colorado governor and U.S. Senator who lobbied for an Interstate Highway to be built across Colorado. The Eisenhower Memorial Bore (westbound tunnel)
2163-487: Is relatively long and narrow; the length is often much greater than twice the diameter , although similar shorter excavations can be constructed, such as cross passages between tunnels. The definition of what constitutes a tunnel can vary widely from source to source. For example, in the United Kingdom, a road tunnel is defined as "a subsurface highway structure enclosed for a length of 150 metres (490 ft) or more." In
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#17328444830592266-401: Is sometimes necessary during the excavation of a tunnel. They are usually circular and go straight down until they reach the level at which the tunnel is going to be built. A shaft normally has concrete walls and is usually built to be permanent. Once the access shafts are complete, TBMs are lowered to the bottom and excavation can start. Shafts are the main entrance in and out of the tunnel until
2369-515: Is that the open building pit is muted after tunnel construction; no roof is placed. Some tunnels are double-deck, for example, the two major segments of the San Francisco–Oakland Bay Bridge (completed in 1936) are linked by a 160-metre (540 ft) double-deck tunnel section through Yerba Buena Island , the largest-diameter bored tunnel in the world. At construction this was a combination bidirectional rail and truck pathway on
2472-673: Is the Siloam Tunnel , built in Jerusalem by the kings of Judah around the 8th century BC. Another tunnel excavated from both ends, maybe the second known, is the Tunnel of Eupalinos , which is a tunnel aqueduct 1,036 m (3,400 ft) long running through Mount Kastro in Samos , Greece. It was built in the 6th century BC to serve as an aqueduct . In Ethiopia , the Siqurto foot tunnel , hand-hewn in
2575-425: Is used during winter in case weather is too bad for vehicles to pass on their own. Convoy driving is initiated when the strong wind quickly fills the road with snow behind snowplows, particularly on mountain passes. Only a limited number of vehicles are allowed for each convoy and convoy leader is obliged to decline vehicles not fit for the drive. Storm convoys are prone to multiple-vehicle collision . Convoy driving
2678-468: Is used for forced air ventilation while the space below the roadway is used for drainage. As of March 2023, more than 434 million vehicles had passed through the tunnel. This figure includes a significant number of visitors to Colorado's ski resorts . Due to additional height restrictions from variable-message signs and lighting systems, the original posted clearance of the tunnels was 13 ft 6 in (4.11 m). The trucking industry lobbied
2781-556: The Balvano train disaster , was caused by a train stalling in the Armi tunnel in Italy in 1944, killing 426 passengers. Designers try to reduce these risks by installing emergency ventilation systems or isolated emergency escape tunnels parallel to the main passage. Government funds are often required for the creation of tunnels. When a tunnel is being planned or constructed, economics and politics play
2884-744: The Battle of the Atlantic was a long struggle as the Germans developed anti-convoy tactics and the British developed counter-tactics to thwart the Germans. The capability of a heavily armed warship against a convoy was dramatically illustrated by the fate of Convoy HX 84 . On November 5, 1940, the German heavy cruiser Admiral Scheer encountered the convoy. Maiden , Trewellard , and Kenbame Head were quickly destroyed, and Beaverford and Fresno City falling afterwards. Only
2987-532: The Blue River ), along with all seepage entering the tunnel, is discharged into Clear Creek for delivery to the Coors Brewing Company . Typically, the tunnel delivers over 300 acre-feet (370,000 m) of water per year. Tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for
3090-475: The Canada convoy protest in 2022. The Highway Code of several European countries (Norway, Italy, Greece, Netherlands, Germany, Austria, Switzerland, possibly more) includes special rights for marked convoys. They have to be treated like a single vehicle. If the first vehicle has passed an intersection, all others may do so without interruption. If other road users overtake the convoy, they are not allowed to split into
3193-563: The Chernobyl disaster in Belarus and Ukraine . The convoys are made possible partly by the relatively small geographic distances between the stable and affluent countries of Western Europe, and the areas of need in Eastern Europe and, in a few cases, North Africa and even Iraq . They are often justified because although less directly cost-effective than mass freight transport, they emphasise
Eisenhower Tunnel - Misplaced Pages Continue
3296-494: The Cold War with its high number of military exercises, the military was the main user of convoy rights. Today, catastrophes like large-scale flooding might bring a high number of flagged convoys to the roads. Large-scale evacuations for the disarming of World War II bombs are another common reason for non-governmental organization (NGO) unit movements under convoy rights. In Norway, "convoy driving" ( Norwegian : kolonnekjøring )
3399-485: The Iran–Iraq War . In the present day, convoys are used as a tactic by navies to deter pirates off the coast of Somalia from capturing unarmed civilian freighters who would otherwise pose easy targets if they sailed alone. The word "convoy" is also associated with groups of road vehicles being driven, mostly by volunteers, to deliver humanitarian aid , supplies, and—a stated objective in some cases—"solidarity". In
3502-464: The Port Authority of New York and New Jersey was not aware of this bill and had not asked for a grant for such a project. Increased taxes to finance a large project may cause opposition. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the groundwater conditions, the length and diameter of
3605-797: The Queens-Midtown Tunnel between Manhattan and the borough of Queens on Long Island ; the Detroit-Windsor Tunnel between Michigan and Ontario ; and the Elizabeth River tunnels between Norfolk and Portsmouth, Virginia ; the 1934 River Mersey road Queensway Tunnel ; the Western Scheldt Tunnel , Zeeland, Netherlands; and the North Shore Connector tunnel in Pittsburgh, Pennsylvania . The Sydney Harbour Tunnel
3708-466: The River Mersey at Liverpool was chosen over a massively high bridge partly for defense reasons; it was feared that aircraft could destroy a bridge in times of war, not merely impairing road traffic but blocking the river to navigation. Maintenance costs of a massive bridge to allow the world's largest ships to navigate under were considered higher than for a tunnel. Similar conclusions were reached for
3811-457: The Spanish treasure fleets , that sailed from the 1520s until 1790. When merchant ships sailed independently, a privateer could cruise a shipping lane and capture ships as they passed. Ships sailing in convoy presented a much smaller target: a convoy was as hard to find as a single ship. Even if the privateer found a convoy and the wind was favourable for an attack, it could still hope to capture only
3914-665: The United Kingdom of digging tunnels in strong clay-based soil structures. This method of cut and cover construction required relatively little disturbance of property during the renewal of the United Kingdom's then ancient sewerage systems. It was also used during the First World War by Royal Engineer tunnelling companies placing mines beneath German lines, because it was almost silent and so not susceptible to listening methods of detection. Tunnel boring machines (TBMs) and associated back-up systems are used to highly automate
4017-591: The canton of Glarus . The borehole has a diameter of 8.03 metres (26.3 ft). The four TBMs used for excavating the 57-kilometre (35 mi) Gotthard Base Tunnel , in Switzerland , had a diameter of about 9 metres (30 ft). A larger TBM was built to bore the Green Heart Tunnel (Dutch: Tunnel Groene Hart) as part of the HSL-Zuid in the Netherlands, with a diameter of 14.87 metres (48.8 ft). This in turn
4120-486: The water table . This pressurizes the ground ahead of the TBM cutter head to balance the water pressure. The operators work in normal air pressure behind the pressurized compartment, but may occasionally have to enter that compartment to renew or repair the cutters. This requires special precautions, such as local ground treatment or halting the TBM at a position free from water. Despite these difficulties, TBMs are now preferred over
4223-480: The 12th century. The use of organized naval convoys dates from when ships began to be separated into specialist classes and national navies were established. By the French Revolutionary Wars of the late 18th century, effective naval convoy tactics had been developed to ward off pirates and privateers . Some convoys contained several hundred merchant ships. The most enduring system of convoys were
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4326-689: The 16th century as a metaphor for a narrow, confined space like the inside of a cask. Some of the earliest tunnels used by humans were paleoburrows excavated by prehistoric mammals. Much of the early technology of tunneling evolved from mining and military engineering . The etymology of the terms "mining" (for mineral extraction or for siege attacks ), " military engineering ", and " civil engineering " reveals these deep historic connections. Predecessors of modern tunnels were adits that transported water for irrigation , drinking, or sewerage . The first qanats are known from before 2000 BC. The earliest tunnel known to have been excavated from both ends
4429-638: The 1960s. The main idea of this method is to use the geological stress of the surrounding rock mass to stabilize the tunnel, by allowing a measured relaxation and stress reassignment into the surrounding rock to prevent full loads becoming imposed on the supports. Based on geotechnical measurements, an optimal cross section is computed. The excavation is protected by a layer of sprayed concrete, commonly referred to as shotcrete . Other support measures can include steel arches, rock bolts, and mesh. Technological developments in sprayed concrete technology have resulted in steel and polypropylene fibers being added to
4532-687: The 1971 Kingsway Tunnel under the Mersey. In Hampton Roads, Virginia , tunnels were chosen over bridges for strategic considerations; in the event of damage, bridges might prevent US Navy vessels from leaving Naval Station Norfolk . Water-crossing tunnels built instead of bridges include the Seikan Tunnel in Japan; the Holland Tunnel and Lincoln Tunnel between New Jersey and Manhattan in New York City ;
4635-414: The 1990s these convoys became common traveling from Western Europe to countries of the former Yugoslavia , in particular Bosnia and Kosovo , to deal with the aftermath of the wars there. They also travel to countries where standards of care in institutions such as orphanages are considered low by Western European standards, such as Romania ; and where other disasters have led to problems, such as around
4738-407: The Colorado Department of Transportation (CDOT) to increase the vertical clearance. In 2007, the tunnel was retrofitted with lower-profile lighting and signs, increasing its clearance by 5 in (13 cm) to 13 ft 11 in (4.24 m). A height detector near each tunnel entrance sounds a siren and turns traffic signals red, stopping all traffic, if an overheight vehicle attempts to enter
4841-589: The Johnson bore was $ 102.8 million (equivalent to $ 432 million in 2024). Not included in the figures is about $ 50 million in non-boring expenses during the construction of both tunnels. Upon opening, it became the highest-elevation tunnel in the world, taking the title from the Salang Tunnel in Afghanistan. The tunnel's construction highlighted issues relevant to the feminist movement. When Janet Bonnema applied for
4944-691: The Middle Ages, crosses a mountain ridge. In the Gaza Strip , the network of tunnels was used by Jewish strategists as rock-cut shelters, in first links to Judean resistance against Roman rule in the Bar Kokhba revolt during the 2nd century AD. A major tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques. An informed choice can then be made of machinery and methods for excavation and ground support, which will reduce
5047-586: The North Atlantic on February 8, 1941. When the Germans detected the slow but well-protected battleship HMS Ramillies escorting the convoy, they fled the scene rather than risk damage from her 15 in (38 cm) guns. The enormous number of vessels involved and the frequency of engagements meant that statistical techniques could be applied to evaluate tactics: an early use of operational research in war. Prior to overt participation in World War II,
5150-643: The South Pacific involved Allied bombers interdicting Japanese troopship convoys which were often defended by Japanese fighters, notable Guadalcanal (13 November 1942), Rabaul (5 January 1943), and the Battle of the Bismarck Sea (2–4 March 1943). At the Battle off Samar , the effectiveness of the U.S. Navy's escorts was demonstrated when they managed to defend their troop convoy from a much larger and more powerful Japanese battle-fleet. The Japanese force comprised four battleships and numerous heavy cruisers, while
5253-559: The U-boats presented themselves as targets to the escorts with increasing possibility of destruction. In this way, the Ubootwaffe suffered severe losses, for little gain, when pressing pack attacks on well-defended convoys. The largest convoy effort since World War II was Operation Earnest Will , the U.S. Navy's 1987–88 escort of reflagged Kuwaiti tankers in the Persian Gulf during
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#17328444830595356-574: The U.S. force consisted of escort carriers, destroyers, and destroyer escorts. Large numbers of American aircraft (albeit without much anti-ship ordnance other than torpedoes) and aggressive tactics of the destroyers (with their radar-directed gunfire) allowed the U.S. to sink three Japanese heavy cruisers at the cost of one escort carrier and three destroyers. The German anti-convoy tactics included: The Allied responses included: They were also aided by Many naval battles of World War II were fought around convoys, including: The convoy prefix indicates
5459-729: The US was actively engaged in convoys with the British in the North Atlantic Ocean, primarily supporting British activities in Iceland. After Germany declared war on the US, the US Navy decided not to organize convoys on the American eastern seaboard. US Fleet Admiral Ernest King ignored advice on this subject from the British, as he had formed a poor opinion of the Royal Navy early in his career. The result
5562-581: The United States, the NFPA definition of a tunnel is "An underground structure with a design length greater than 23 m (75 ft) and a diameter greater than 1,800 millimetres (5.9 ft)." The word "tunnel" comes from the Middle English tonnelle , meaning "a net", derived from Old French tonnel , a diminutive of tonne ("cask"). The modern meaning, referring to an underground passageway, evolved in
5665-414: The best efforts of engineers, three workers were killed boring the first tube and four in boring the second. Further complicating construction, the boring machines could not work as fast as expected at such high elevations and so the productivity was significantly less than planned. The frustration prompted one engineer to comment, "We were going by the book, but the damned mountain couldn't read." Though
5768-400: The blocky nature of rocks, the exact location of fault zones, or the stand-up times of softer ground. This may be a particular concern in large-diameter tunnels. To give more information, a pilot tunnel (or "drift tunnel") may be driven ahead of the main excavation. This smaller tunnel is less likely to collapse catastrophically should unexpected conditions be met, and it can be incorporated into
5871-498: The concrete mix to improve lining strength. This creates a natural load-bearing ring, which minimizes the rock's deformation . By special monitoring the NATM method is flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work. The measured rock properties lead to appropriate tools for tunnel strengthening . In pipe jacking , hydraulic jacks are used to push specially made pipes through
5974-553: The east portal. A Martin 4-0-4 charter aircraft, one of two carrying the college football team of Wichita State University , crashed just north of the highway ( 39°41′37″N 105°52′57″W / 39.6935°N 105.8825°W / 39.6935; -105.8825 ). Of the 40 passengers and crew on board, only nine survived. The team was on its way to a game with Utah State University in Logan and had recently refueled at Denver's Stapleton International Airport . The plane carrying
6077-512: The eastbound Edwin C. Johnson tunnel on August 18, 1975, and finished on December 21, 1979. The initial engineering cost estimate for the Eisenhower bore was $ 42 million, but the actual cost was $ 108 million (equivalent to $ 741 million in 2024). Approximately 90% of the funds were paid by the federal government, with the state of Colorado paying the rest. At the time, it set a record for the most expensive federally aided project. The excavation cost for
6180-409: The entire tunnelling process, reducing tunnelling costs. In certain predominantly urban applications, tunnel boring is viewed as a quick and cost-effective alternative to laying surface rails and roads. Expensive compulsory purchase of buildings and land, with potentially lengthy planning inquiries, is eliminated. Disadvantages of TBMs arise from their usually large size – the difficulty of transporting
6283-508: The escorting warships to the sometimes hazardous conditions of the North Atlantic, with only rare occurrences of visible achievement (i.e. fending off a submarine assault). The British adopted a convoy system, initially voluntary and later compulsory for almost all merchant ships, the moment that World War II was declared. Each convoy consisted of between 30 and 70 mostly unarmed merchant ships. Canadian, and later American, supplies were vital for Britain to continue its war effort. The course of
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#17328444830596386-441: The final tunnel or used as a backup or emergency escape passage. Alternatively, horizontal boreholes may sometimes be drilled ahead of the advancing tunnel face. Other key geotechnical factors: For water crossings, a tunnel is generally more costly to construct than a bridge. However, both navigational and traffic considerations may limit the use of high bridges or drawbridges intersecting with shipping channels, necessitating
6489-405: The ground behind a TBM or shield. This method is commonly used to create tunnels under existing structures, such as roads or railways. Tunnels constructed by pipe jacking are normally small diameter bores with a maximum size of around 3.2 metres (10 ft). Box jacking is similar to pipe jacking, but instead of jacking tubes, a box-shaped tunnel is used. Jacked boxes can be a much larger span than
6592-598: The highest vehicular tunnel in the US, and longest mountain tunnel and highest point on the Interstate Highway System, higher tunnels have since been constructed elsewhere, such as the Fenghuoshan Tunnel , a rail tunnel in China. The tunnel bores measure 48 ft × 40 ft (15 m × 12 m). The traveled portion is a rectangular shape just over 16 ft (4.9 m) tall. The space above this
6695-636: The immersed-tube type), while deep tunnels are excavated, often using a tunnelling shield . For intermediate levels, both methods are possible. Large cut-and-cover boxes are often used for underground metro stations, such as Canary Wharf tube station in London. This construction form generally has two levels, which allows economical arrangements for ticket hall, station platforms, passenger access and emergency egress, ventilation and smoke control, staff rooms, and equipment rooms. The interior of Canary Wharf station has been likened to an underground cathedral, owing to
6798-435: The inevitable smoke and steam. A major disadvantage of cut-and-cover is the widespread disruption generated at the surface level during construction. This, and the availability of electric traction, brought about London Underground's switch to bored tunnels at a deeper level towards the end of the 19th century. Prior to the replacement of manual excavation by the use of boring machines, Victorian tunnel excavators developed
6901-468: The large TBM to the site of tunnel construction, or (alternatively) the high cost of assembling the TBM on-site, often within the confines of the tunnel being constructed. There are a variety of TBM designs that can operate in a variety of conditions, from hard rock to soft water-bearing ground. Some TBMs, the bentonite slurry and earth-pressure balance types, have pressurized compartments at the front end, allowing them to be used in difficult conditions below
7004-607: The lower deck with automobiles above, now converted to one-way road vehicle traffic on each deck. In Turkey, the Eurasia Tunnel under the Bosphorus , opened in 2016, has at its core a 5.4 km (3.4 miles) two-deck road tunnel with two lanes on each deck. Additionally, in 2015 the Turkish government announced that it will build three -level tunnel, also under the Bosporus. The tunnel
7107-417: The main reason that the British Admiralty did not adopt convoy tactics at the start of the first Battle of the Atlantic in World War I . But the German capital ships had been bottled up in the North Sea, and the main threat to shipping came from U-boats . From a tactical point of view, World War I–era submarines were similar to privateers in the age of sail. These submarines were only a little faster than
7210-421: The merchant ships they were attacking, and capable of sinking only a small number of vessels in a convoy because of their limited supply of torpedoes and shells. The Admiralty took a long time to respond to this change in the tactical position, and in April 1917 convoys were trialled, before being officially introduced in the Atlantic in September 1917. Other arguments against convoys were raised. The primary issue
7313-413: The older method of tunnelling in compressed air, with an airlock/decompression chamber some way back from the TBM, which required operators to work in high pressure and go through decompression procedures at the end of their shifts, much like deep-sea divers . In February 2010, Aker Wirth delivered a TBM to Switzerland, for the expansion of the Linth–Limmern Power Stations located south of Linthal in
7416-540: The operation of empty and loaded trains at the same time. The temporary way is replaced by the permanent way at completion, thus explaining the term " Perway ". The vehicles or traffic using a tunnel can outgrow it, requiring replacement or enlargement: An open building pit consists of a horizontal and a vertical boundary that keeps groundwater and soil out of the pit. There are several potential alternatives and combinations for (horizontal and vertical) building pit boundaries. The most important difference with cut-and-cover
7519-417: The prime targets of speed traps . Most truckers had difficult schedules to keep and as a result had to maintain a speed above the posted speed limit to reach their destinations on time. Convoys were started so that multiple trucks could run together at a high speed with the rationale being that if they passed a speed trap the police would only be able to pull over one of the trucks in the convoy. When driving on
7622-510: The project is completed. If a tunnel is going to be long, multiple shafts at various locations may be bored so that entrance to the tunnel is closer to the unexcavated area. Once construction is complete, construction access shafts are often used as ventilation shafts , and may also be used as emergency exits. The New Austrian Tunnelling method (NATM)—also referred to as the Sequential Excavation Method (SEM) —was developed in
7725-409: The project was supposed to take three years, the tunnel was not opened to traffic until a March 8, 1973, dedication ceremony by Governor John Love . Initially, the northern Eisenhower bore was used for two-way traffic, with one lane for each direction. The amount of traffic through the tunnel exceeded predictions, and efforts soon began to expedite construction on the southern bore. Construction began on
7828-426: The project went well over time and budget. One of the biggest setbacks was the discovery of fault lines in the path of the tunnel that were not discovered during the pilot bores. The first construction contractor went bankrupt excavating rock in this fault zone. These faults began to slip during construction and emergency measures had to be taken to protect the tunnels and workers from cave-ins and collapses. Despite
7931-485: The proper machinery must be selected. Large infrastructure projects require millions or even billions of dollars, involving long-term financing, usually through issuance of bonds . The costs and benefits for an infrastructure such as a tunnel must be identified. Political disputes can occur, as in 2005 when the US House of Representatives approved a $ 100 million federal grant to build a tunnel under New York Harbor. However,
8034-502: The queue. Clear and uniform marking has been required in court decisions for these rights to apply. Operating such convoy usually needs special permission, but there are exemptions for emergency and catastrophe intervention. Common practice is, to operate with the same style of marking as NATO convoys: STANAG 2154 marking plus country-specific augmentation listed in Annex B to the STANAG. During
8137-482: The risk of encountering unforeseen ground conditions. In planning the route, the horizontal and vertical alignments can be selected to make use of the best ground and water conditions. It is common practice to locate a tunnel deeper than otherwise would be required, in order to excavate through solid rock or other material that is easier to support during construction. Conventional desk and preliminary site studies may yield insufficient information to assess such factors as
8240-403: The route of the convoy. For example, 'PQ' would be Iceland to Northern Russia and 'QP' the return route. The success of convoys as an anti-submarine tactic during the world wars can be ascribed to several reasons related to U-boat capabilities, the size of the ocean and convoy escorts. In practice, Type VII and Type IX U-boats were limited in their capabilities. Submerged speed and endurance
8343-552: The sacrifices of the armed merchant cruiser HMS Jervis Bay and the freighter Beaverford to stall the Scheer , in addition to failing light, allowed the rest of the convoy to escape. The deterrence value of a battleship in protecting a convoy was also dramatically illustrated when the German light battleships (referred by some as battlecruisers) Scharnhorst and Gneisenau , mounting 11 in (28 cm) guns, came upon an eastbound British convoy ( HX 106 , with 41 ships) in
8446-528: The sheer size of the excavation. This contrasts with many traditional stations on London Underground , where bored tunnels were used for stations and passenger access. Nevertheless, the original parts of the London Underground network, the Metropolitan and District Railways, were constructed using cut-and-cover. These lines pre-dated electric traction and the proximity to the surface was useful to ventilate
8549-469: The state of Colorado lobbied for the Interstate Highway System to route a transcontinental highway across Colorado. After a round of negotiations with Utah officials, it was decided the best option was to follow the US Route 6 corridor. Engineers recommended tunneling under the pass, rather than attempt to build a route across conforming to Interstate Highway standards . The Eisenhower–Johnson Memorial Tunnel
8652-664: The submarine had escaped damage, it would have to remain submerged for its own safety and might only recover its position after many hours' hard work. U-boats patrolling areas with constant and predictable flows of sea traffic, such as the United States Atlantic coast in early 1942, could dismiss a missed opportunity in the certain knowledge that another would soon present itself. The destruction of submarines required their discovery, an improbable occurrence on aggressive patrols, by chance alone. Convoys, however, presented irresistible targets and could not be ignored. For this reason,
8755-405: The support of large numbers of small groups, and are quite distinct from multinational organisations such as United Nations humanitarian efforts. Truckers' convoys consisting of semi-trailer trucks and/or petrol tankers are more similar to a caravan than a military convoy. Truckers' convoys were created as a byproduct of the U.S.' national 55 mph speed limit and 18-wheelers becoming
8858-608: The team's starters departed Denver and traveled a poorly planned scenic route. The other plane, carrying reserve players, followed the original route and landed safely in Logan. While the Eisenhower Tunnel was primarily intended as a transportation tunnel, it also serves as a water tunnel for water diversion from the western side of the Continental Divide to the eastern side. Water from the Straight Creek watershed (a tributary of
8961-400: The tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and the shape of the tunnel and appropriate risk management. There are three basic types of tunnel construction in common use. Cut-and-cover tunnels are constructed in a shallow trench and then covered over. Bored tunnels are constructed in situ, without removing the ground above. Finally,
9064-459: The tunnel has largely supplanted the older route of U.S. Highway 6 over Loveland Pass , hazardous material carriers (hazmats), bicycles, and pedestrians are prohibited from the tunnel and must use the pass, which is longer, steeper, and 834 ft (254 m) higher at 11,992 ft (3,655 m). And while the tunnel's route is less formidable than the pass, its approaches are steep nonetheless and have runaway truck ramps . If Loveland Pass
9167-407: The tunnel) or due to snow and ice atop the trailer. During this time, the trucking industry estimated the number of alarms would drop by as much as 80% if the clearance could be raised even a few inches. The 2007 retrofit also added a weigh-in-motion system that calculates a safe speed for trucks on the 7% grades and curves on the departures from the tunnels and displays it to each driver. While
9270-406: The tunnel, with an entourage of reporters, on November 9, 1972. Some workers walked off the job, and at least one of them yelled, "Get those women out of here." She remained determined and re-entered the tunnel a few days later. The next time, she dressed in coveralls and was even assigned tasks on the roof of the tunnel overlooking the men below. Surprised that nobody had apparently noticed that she
9373-401: The tunnel. The entrance will remain closed until the vehicle is removed from the freeway, which can cause severe delays. CDOT noted that prior to the retrofit, about 20,000 vehicles per year tripped the alarm. The trucking industry argued that many of these trucks were under the height requirement but tripped the alarm due to their air suspensions (which can be lowered during their journey through
9476-422: The two portals common at each end, though there may be access and ventilation openings at various points along the length. A pipeline differs significantly from a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods. A tunnel may be for foot or vehicular road traffic , for rail traffic, or for a canal . The central portions of
9579-428: The two most common being bored tunnels or immersed tubes , examples are Bjørvika Tunnel and Marmaray . Submerged floating tunnels are a novel approach under consideration; however, no such tunnels have been constructed to date. During construction of a tunnel it is often convenient to install a temporary railway, particularly to remove excavated spoil , often narrow gauge so that it can be double track to allow
9682-467: Was a woman, she stated, "I had a good disguise." Bonnema continued to dress in coveralls during her subsequent work in the tunnel so as not to attract attention. In November 2023, CDOT opened an updated operations center and new garage bays at the tunnels. On Friday, October 2, 1970, during the tunnel's construction, workers constructing the tunnel were among the first on scene of a plane crash that had occurred less than two miles (3.2 km) northeast of
9785-563: Was allowed to sail unescorted. In the early 20th century, the dreadnought changed the balance of power in convoy battles. Steaming faster than merchant ships and firing at long ranges, a single battleship could destroy many ships in a convoy before the others could scatter over the horizon. To protect a convoy against a capital ship required providing it with an escort of another capital ship, at very high opportunity cost (i.e. potentially tying down multiple capital ships to defend different convoys against one opponent ship). Battleships were
9888-566: Was constructed to provide a second harbour crossing and to alleviate traffic congestion on the Sydney Harbour Bridge , without spoiling the iconic view. Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties with tides, weather, and shipping during construction (as in the 51.5-kilometre or 32.0-mile Channel Tunnel ), aesthetic reasons (preserving the above-ground view, landscape, and scenery), and also for weight capacity reasons (it may be more feasible to build
9991-537: Was known as the Straight Creek Tunnel during construction, named for the waterway that runs along the western approach to the tunnel. Before the tunnel was dedicated, it was renamed to honor Dwight D. Eisenhower and Edwin C. Johnson. The original Pioneer bore to access the two larger bores was "holed through" in late 1964, after fourteen months. Construction on the first bore of the tunnel was started on March 15, 1968. Construction efforts suffered many setbacks and
10094-432: Was limited and not suited for overhauling many ships. Even a surfaced U-boat could take several hours to gain an attack position. Torpedo capacity was also restricted to around fourteen (Type VII) or 24 (Type IX), thus limiting the number of attacks that could be made, particularly when multiple firings were necessary for a single target. There was a real problem for the U-boats and their adversaries in finding each other; with
10197-570: Was small compared with the loss of productivity due to ships being sunk. Ports could deal more easily with convoys because they tended to arrive on schedule and so loading and unloading could be planned. In his book On the Psychology of Military Incompetence , Norman Dixon suggested that the hostility towards convoys in the naval establishment were in part caused by a (sub-conscious) perception of convoys as effeminating, due to warships having to care for civilian merchant ships. Convoy duty also exposes
10300-701: Was superseded by the Madrid M30 ringroad , Spain, and the Chong Ming tunnels in Shanghai , China. All of these machines were built at least partly by Herrenknecht . As of August 2013 , the world's largest TBM was " Big Bertha ", a 17.5-metre (57.5 ft) diameter machine built by Hitachi Zosen Corporation , which dug the Alaskan Way Viaduct replacement tunnel in Seattle, Washington (US). A temporary access shaft
10403-635: Was the loss of productivity, as merchant shipping in convoy has to travel at the speed of the slowest vessel in the convoy and spent a considerable amount of time in ports waiting for the next convoy to depart. Further, large convoys were thought to overload port resources. Actual analysis of shipping losses in World War I disproved all these arguments, at least so far as they applied to transatlantic and other long-distance traffic. Ships sailing in convoys were far less likely to be sunk, even when not provided with an escort. The loss of productivity due to convoy delays
10506-479: Was too late. In the early part of the conflict, American submarines in the Pacific were ineffective as they suffered from timid tactics, faulty torpedoes, and poor deployment, while there were only small numbers of British and Dutch boats. U.S. Admiral Charles A. Lockwood 's efforts, coupled with strenuous complaints from his captains, rectified these problems and U.S. submarines became much more successful by war's end. As
10609-594: Was what the U-boat crews called their Second Happy Time , which did not end until convoys were introduced. In the Pacific Theater of World War II, Japanese merchant ships rarely traveled in convoys. Japanese destroyers were generally deficient in antisubmarine weaponry compared to their Allied counterparts, and the Japanese navy did not develop an inexpensive convoy escort like the Allies' destroyer escort / frigate until it
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