Tunnel

February 18, 2010 by · Leave a Comment 

tufail-tunnel

A tunnel is an underground passageway. The definition of what constitutes a tunnel is not universally agreed upon. However, in general tunnels are at least twice as long as they are wide. In addition, they should be completely enclosed on all sides, save for the openings at each end. Some civic planners define a tunnel as 0.1 miles (0.16 km) in length or longer, while anything shorter than this should be called an underpass or a chute. For example, the underpass beneath Yahata Station in Kitakyushu, Japan is only 0.08 miles (0.13 km) long and therefore should not be considered a tunnel.

A tunnel may be for pedestrians or cyclists, for general road traffic, for motor vehicles only, for rail traffic, or for a canal. Some are aqueducts, constructed purely for carrying water — for consumption, for hydroelectric purposes or as sewers — while others carry other services such as telecommunications cables. There are even tunnels designed as wildlife crossings for European badgers and other endangered species. Some secret tunnels have also been made as a method of entrance or escape from an area, such as the Cu Chi Tunnels or the tunnels connecting the Gaza Strip to Egypt. Some tunnels are not for transport at all but are fortifications, for example Mittelwerk and Cheyenne Mountain.

In the United Kingdom a pedestrian tunnel or other underpass beneath a road is called a subway. This term was used in the past in the United States, but now refers to underground rapid transit systems.

The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. Rail stations with much traffic usually provide pedestrian tunnels from one platform to another, though others use bridges.

It is essential that any tunnel project starts with a comprehensive investigation of ground conditions. The results of the investigation will allow proper choice of machinery and methods for excavation and ground support, and will reduce the risk of encountering unforeseen ground conditions. In the early stages, the horizontal and vertical alignment will be optimized to make use of the best ground and water conditions.

In some cases, conventional desk and site studies will not produce sufficient information to assess, for example, the blocky nature of rocks, the exact location of fault zones, or stand-up times of softer ground. This may be a particular concern in large diameter tunnels. To overcome these problems, a pilot tunnel, or drift, may be driven ahead of the main drive. This smaller diameter tunnel will be easier to support when unexpected conditions occur, and will be incorporated in the final tunnel. Alternatively, horizontal boreholes may sometimes be used ahead of the advancing tunnel face.

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Chaos on Cairo Streets

May 7, 2009 by · Leave a Comment 

By Sumayyah Meehan MMNS Middle East Correspondent

cairo Cars on bustling Cairo streets compete with pedestrians, donkey carts, buses and motorcycles as they make their way down the ever congested and polluted roadways. And that’s in addition to sharing the street with countless other vehicles. As a result of the chaos, Egypt is ranked as 2nd in the world for traffic fatalities. According to a World Health Organization report, there were an estimated 7,000 road fatalities in Egypt last year alone. The reasons for the deaths can be chalked up to several factors such as poor driving skills by motorists, a failing infrastructure with poor roadways and a general indifference by a population who is one of the poorest in the world.

Most drivers in Egypt do not even have to pass a driver’s education course before they are licensed to hit the road. This is evident the moment you pull onto any street in Cairo. Driver’s weave in and out of traffic and get off at exits without even turning on their blinkers. Since bus stops are few and far between, buses often stop in the middle of the roadway to dispense their passengers, who just might get hit by a speeding motorist the minute they get off the bus. The speed limit is too often ignored and even traffic stoplights serve as mere road ornaments as driver after driver blow through the red lights.

Taking a look inside a typical vehicle driven by an Egyptian citizen reveals a whole new world of hazards and violations. For one thing, most seatbelts are either missing or tucked down into the seat without even a thought to their purpose being taken into consideration. The occupants of the car are jostled about unrestrained, which includes children who often use the car as an excuse to jump around and play. A children’s carseat in an Egyptian car is an unfortunate rarity. There are also countless distractions that cause the driver to keep his eyes off of the road, which includes hot beverages like tea, cell phones and the all too common cigarette balanced between fingers.

There are an estimated 4.4 million cars on Egyptian streets and the number is growing. The Egyptian government is fighting an uphill battle in combating the roadway mayhem. However, parliament has recently taken measures to punish those who break traffic safety laws and hopefully send a message to others that reckless driving is no longer acceptable. Last year a new traffic safety code was adopted in Egypt. Simple traffic transgressions, such as not yielding to pedestrians or driving in the opposite direction on a one-way street, are now punishable by jail time and a hefty fine.

The government has shrewdly turned to technology to maintain some level of road safety. Egyptian roads are now monitored by cameras, which are remotely manned by a control center that operates around the clock. A system of radars has also been established at congested intersections to catch traffic violators in the act. Policemen have also been equipped with portable digital devices to quickly issue citations. And the government plans to study traffic accident patterns to prevent future calamities.

The Ministry of Interior has also launched a media campaign to educate the public about the importance of road safety. This month the ministry plans to launch a monthly documentary about specific traffic accidents that resulted in one or more fatalities. The documentary will show viewers, up close and personal, the reason for the accident and how it could have been prevented. The ministry also plans to go a step further by interviewing family members of the deceased to see how traumatic their loss has been. The Egyptian government hopes that the programming will wake its’ populous out of their slumber to take road safety seriously.

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