"Today on "Impossible engineering"..." "The Gotthard base tunnel... the longest tunnel in the world." "A staggering 35 miles through the heart of the Swiss Alps..." "Firing!" "...it took revolutionary engineering." "...to make the impossible, possible. captions paid for by Discovery communications" "The Alps, the tallest mountain range in Europe." "At its heart is the Gotthard pass, a crucial route linking the north and south." "Traffic has increased tenfold in recent decades." "The mountain passes are at a standstill." "The solution?" "Bore a tunnel directly through the mountain range." "The Gotthard base tunnel will be 35 miles long and a mile and a half underground." "Constructing a tunnel this long is dangerous business." "Before any digging can begin, engineers need to be sure that the earth deep beneath the Swiss Alps is safe for boring." "Geophysicist dirk krueger's job is to reduce risk as much as possible." "Rock conditions under the Alps can change from foot to foot." "The location of the proposed tunnel is too deep to sample from above-ground." "There's no way to predict what dangers lie ahead for the digging team." "Drilling blindly into the earth could be deadly." "Dirk needs a solution before the team can dig." "It's a challenge that would have been impossible without an invention from the 19th century." "Japan is the most seismically active country on earth." "Around 1,500 quakes occur each year." "For centuries, no one knew where or why they struck." "That was until 1880, when British engineer John Milne experienced an earthquake while surveying in Japan and began recording what he felt." "What I've created here is a simple demonstration of a seismograph." "I've got a pen attached to a pendulum." "When I shake the table and pull the paper through, you will start to see the pen record the number of shakes on the paper, and that represents the frequency and the amplitude, or the number of times per second of the shakes" "and the size of those shakes." "So let g'sive it a try." "My assistant Kirk here is going to come and shake the table and as I pull the paper through you can start to see the trace on the paper and then if Kirk gives it a really big shake." "You can see the increase in amplitude, and then as it calms down, it gets less again." "And we can see here where the really big shake was compared to the rest of the time." "It's really simple, but quite effective demonstration of how a seismograph works." "John Milne devised the first continuously running seismographs, helping detect the epicenter of quakes in Japan." "His design is still used all over the world." "Engineers at the Gotthard base tunnel are using Milne's seismographs in an innovative way to help them paint a picture of what's in store." "They are testing their new system today at the V.S.H. Hagerbach tunnel research facility." "Explosive charges are placed within the rock face." "Each detonation sends out shock waves which are measured by the engineering team." "Changes in the rock show up as a shift in the wave pattern providing a clue to what dangers lie ahead for the drilling team." "Construction begins on history's most ambitious subterranean project in 1996." "The route consists of two tunnels." "Teams drill from opposite sides of the mountain with the ultimate goal of joining up in the middle, deep underneath the Swiss Alps." "But to pull off the seemingly impossible, the team is going to have to break out the big guns." "These machines are really very amazing." "You have to imagine it's 400-meter long, the whole machine." "In the mountains of Switzerland, engineers are undertaking one of history's most audacious construction projects a 35-mile tunnel driven straight through the Alps." "It is the longest and deepest ever built." "Renzo Simoni is on the team charged with achieving the impossible." "So how do you dig 35 miles through a mountain range?" "It's a challenge that would've been impossible without an invention from the 19th century." "London, England." "Every day, four million people descend into a complex network of tunnels, more than 20 of which crisscross beneath the river thames." "But it wasn't always this way." "By the early 19th century, Londoners had given up all hope of having a tunnel beneath the river." "Several previous attempts to tunnel under the thames had failed and the problem was the soft and malleable London clay and sand." "Hard rock miners had come from Cornwall, but the techniques they used on hard rock had failed, leading to collapse and flooding." "Eventually it was decided that the project was impossie, bl and it was written off." "Engineer Marc Brunel had a radical idea." "Brunel observed the perfect tunnel-like structures left by shipworms as they burrow through timber." "As it digs, this marine mollusk shoves pulpwood into its mouth and digests it, and its bivalved head and hard shell help support the creature as it moves through the wood." "The pulp is then excreted as a hard brittle residue that lines the rear space, creating a tunnel-like structure." "The key is to not actually suck all the sand out of the tube." "The mollusk then uses its back legs to grip itself to the side of the tunnel and push itself forward into the space that it has created repeating the process until it finds light at the end of the tunnel." "And this is exactly the process that Brunel sought to emulate." "Brunel's idea started an underground revolution, some of which can still be found." "Now this place is really incredible, really amazing." "Through a tiny door up at the street, down a rickety old scaffolding, and we find ourselves here in this cathedral-keli space." "Brunel dug the first-ever tunnel under the river thames using his engineering equivalent of a shipworm." "A mobile steel framework called a tunneling shield acts like the worm's hard head, supporting the earth and preventing collapse." "Working in individual compartments, miners excavate just four inches before the whole tunneling shield is pushed forward using screw jacks." "A second group of men working behind them line the tunnel with bricks to prevent its collapse." "Finished in 1843," "Brunel's thames tunnel was hailed as the eighth wonder of the world with almost 50,000 visitors on opening day." "Today it forms part of the London rail network, and it all began in this hidden chamber." "Most people would have no idea that it's here." "But of course, it's importance to engineering and to tunnel engineering in particular, really can't be overstated." "The Gotthard base tunnel is 140 times longer than Brunel's thames tunnel." "To dig 35 miles through the Alps," "Renzo and his team are using a supersized version of Brunel's 19th-century excavator." "At over 1,300 feet long, tunnel boring machines, or T.B.M.S, are almost the same length as the thames tunnel." "They weigh 300 tons, making them the biggest vehicles on earth." "They are so huge they need to be shipped in sections and assembled on site." "As the T.B.M. Head turns, it exerts 35 tons of force, chipping away the rock." "Excavated rock passes through the machine and onto a conveyor." "The T.B.M pushes into the void using hydraulic legs." "These mechanical mollusks munch through 130 feet of rock a day." "In the wake of the T.B.M., the walls are sprayed with shotcrete, a form of liquid concrete." "But how will two teams digging on opposite sides of the Swiss Alps meet in the middle?" "Calculating a straight route is difficult enough above ground." "There are trees, hills, and buildings in the way." "Using landmarks to navigate or relying on towers to get direct sightlines helps." "When plotting a course underground, even the slightest miscalculation could yield disastrous results." "In Switzerland, engineers are undertaking one of history's most audacious construction projects." "To reduce gridlock and pollution, they're attempting to build the longest and deepest tunnel in the world." "The Gotthard base tunnel will slice a 35-mile route straight through the Swiss Alps." "But with two teams digging on opposite sides of the mountain range, engineers face the challenge of meeting in the middle." "Getting the T.B.M.'S meeting in the middle is a very, very big challenge because we have so long distances." "The solution comes from one of the greatest innovations of the 20th century." "In 1960, Theodore Maiman built the world's first laser." "He bought his materials out of catalogs." "Maiman placed a small ruby inside a photographer's flash bulb." "His invention changed the world, allowing highly-accurate measurements to be taken over great distances." "Less than a decade after Maiman's prototype, lasers were bounced off reflectors on the surface of the moon, so the Apollo 11 crew could accurately calculate their distance from earth." "At the Gotthard base tunnel in Switzerland, lasers guide huge tunnel boring machines." "G.P.S. maps the entire route." "But witho nsatellite signal below ground, each T.B.M. relies on a geodetic guidance system to stay on course." "A laser theodolite is attached to the tunnel wall." "It fires a beam at a target on the front of the T.B.M." "As the T.B.M.S chew through the mountain side, they hit unstable earth deep under the Swiss Alps as the T.B.M.S chew through the mountain side, bringing the whole operation to a grinding halt." "Squeezing occurs when the pressure of the mountain pushes against weaker rock." "In extreme cases, it results in the tunnel closing up again after it's been bored." "If the team uses a tunnel boring machine in a squeezing rock zone, the consequences could be disastrous." "So the dig team must go back to basics, using techniques championed in the days long before tunnel boring machines." "Engineer Luke Bisby is in Cornwall on the southwest tip of britain." "He is exploring an area once dependent on tunneling." "So it is hard to believe that 200 years ago underneath the sea was the largest concentration of submarine tin and copper mines anywhere in the world." "This region was the world's largest producer of copper and tin in the 19th century." "There are an estimated 30 to 40 miles of mine shafts beneath the waves." "More than 2,000 mines like this one would have dotted the county." "Cornish miners were considered the best in the business." "Their expertise was sought after for tunneling projects all over the world." "By today's standards, their methods were incredibly inefficient and dangerous." "So this is black powder." "This is the world's first chemical explosive." "It's better known as gunpowder." "Early miners bored hos leby hand, then laid the explosives." "I'm going to light the fuses and then we should have more than a minute to head down the tunnel." "Oh!" "All right, okay, so let's see what's happened here." "Keeping in mind that it would have taken a couple of hours to drill each of these holes by hand, to then put the black powder in and only move that amount of rock despite a pretty big bang," "is a bit disappointing frankly." "The miners would come back inking that the charge hadn't gone off." "The charge would then detonate quite late, and the miners could be maimed or even killed, and in many cases, they were." "The invention of a new, more powerful explosive proved even more dangerous." "So what I have here is a jar of nitroglycerine, and it was first synthesized in 1847." "And you can see just how volatile it is." "If I take a small drop and place it on the steel plate and then I hit it with a hammer." "So where black powder needs a heated charge in order to coax an explosion, nitroglycerine just needs a small tap, and of course down a mine, that could spell disaster." "Swedish explosives expert Alfred Nobel's brother died in a nitroglycerine accident in the 1800s." "After the incident, he was determined to create a safer alternative." "He realized that if he took nitroglycerine and mixed it with kieselguhr which is a naturally occurring clay-like material, he would end up with dynamite." "And you can see that it's quite loose but quite malleable and it could be rolled to eventually form dynamite sticks." "To make his dynamite, Nobel had to figure out a way to safely handle vast amounts of nitroglycerine." "He found his solution in Scotland." "Nobel really favored this area because of its remoteness, and the Sandy soil allowed him to shape the landscape around his factory to protect production workers from potential explosions." "It also allowed him to build mounds, such as thesare ound us." "And on top of these, he could place his nitroglycerine production huts." "In each nitroglycerine hut, one man was in charge of monitoring the temperature and another mixed, sitting on a one-legged stool to ensure he kept his focus." "But sensitivity to temperature and friction meant that nitroglycerine couldn't be safely pumped, and so it was set to trickle down from the huts to the factory, letting gravity do the work." "Once it reached the factory, it was mixed with clay before being rolled into stickofs dynamite." "Nobel had created a product that was now so stable that it could be dropped on the ground or even thrown into fires without exploding." "The new dynamite, along with the invention of pneumatic powered rock drills, gave birth to a quicker anmod re efficient form of tunneling called "drill and blast"..." "All right, that's it." "Let's get out of here." "...Ushering in a new age of mining." "3, 2, 1, firing." "Wow, so that was quite something." "Lot of power in that one." "So we can really see here the power of the dynamite as compared to the black powder." "The dynamite has tenak that entire mass of rock and thrown it sideways." "You can see what a game changer this would have been for the miners working down here." "Whenever engineers at the Gotthard base tunnel encounter rock too soft for the massive tunnel boring machines, they revert to the drill and blast method but with a 21st-century twist." "Known as jumbos, these 60-ton drilling rigs make drilling and blasting easier than ever before." "Each 10-foot arm has a powerful electrohydraulic drill to bore holes for the explosives." "As one arm drills, thope erator lines up another." "Modern emulsion explosives are only active when mixed together at the rock face, much safer than drilling and blasting using traditional dynamite." "Each detonation takes eight hours to prep making drilling and blasting much slower than the T.B.M.S." "But without it, finishing the tunnel would be impossible." "But as the team drills further into the Alps, it's becoming difficult to hold back the enormous pressure of the mountain above." "They need a solution fast." "The Gotthard base tunnel is an epic engineering project." "Massive 1,300-foot tunnel boring machines are grinding away 130 feet of rock each day with the goal of completing a 35-mile long tunnel directly through the Swiss Alps... the longest tunnel in the world." "The team is nearing the finish line, but the immense pressure of the mountains above is slowly closing the tunnel back in on itself, not long after a stretch has been bored." "The steel arches used to hold back the mountain are failing." "The success of the whole project is in jeopardy." "Engineers need an answer fast." "In 1932, engineers Heinrich Toussaint and Egmont Heintzmann revolutionized the German coal mining industry when they invented the t.H. Yielding steel arch support." "Capable of withstanding huge pressure without collapsing, they made it possible to excavate deeper than ever before." "Unlike a conventional rigid steel arch, the jointed concentric rings of their design change shape to accommodate the pressure of the rock, rather than totally resist it." "The solution is to bore a tunnel with a wider circumference than is needed." "The yielding rings allow just enough movement to prevent the supports from collapsing, resisting the pressure of the squeezing rock enough to keep it from closing the tunnel completely." "On October 15, 2010, after 14 years of digging, boring, and blasting, e thdream becomes a reality." "A T.B.M. Crashes through the final few feet of rock." "The two halves of the tunnel join for the first time." "Bravo!" "Thanks to a cutting-edge laser-guidance system, the T.B.M.S complete their monumental job with incredible accuracy, excavating more than 70 miles of rock." "With the digging done, the engineering team turns to their biggest challenge yet, making sure the 35-mile-long tunnel is safe for the thousands of people that will pass through." "The Gotthard base tunnel in Switzerland is a true feat of underground engineering." "With passengers and freight traveling at high speeds through 35 miles of confined space under a mile and a half of solid rock, an accident would be catastrophic." "For Renzo and his team, memories of onofe Europe's worst traffic accidents in another alpine tunnel are on their minds." "In 1999, a truck caught fire in the middle of the 6-mile-long mont blanc tunnel linking France and Italy." "The tunnel quickly filled with smoke, as the Blaze engulfed over 30 vehicles." "The inferno raged for over two days." "39 people lost their lives, most due to smoke inhalation." "To ensure the Gotthard base tunnel is the safest ever built, its engineers are taking inspiration from the innovations of the past." "In the U.K., a groundbreaking engineering project below Liverpool's river Mersey changed tunnel safety forever." "So this is the Queensway tunnel." "And when it opened, it was the biggest and longest underwater road tunnel in the world." "Opened in 1934, it took 1,700 men over 8 years to construct." "But it is not the digging of this tunnel that makes it revolutionary." "About 30,000 cars travel through this tunnel every day, and even with modern exhaust systems, that's a lot of fumes." "And the engineering innovation in this tunnel is what solved that." "By the early-20th century, tunnel engineers had to contend with toxic fumes from the cars using them." "To keep poisonous fumes at bay, the builders of the Mersey tunnel turned to physiologist, John Scott Haldane." "And this is what they came up with." "It is the world's largest ventilation system, and incredibly, this system is still in use today." "In each of the six huge ventilation towers, fresh air drawn in at roof level is pumped underneath the roadway before being blown into the tunnel through ducts along its sides." "At the same time, exhaust fans draw toxic fumes out through holes in the roof." "The George's dock ventilation tower is home to six massive fans circulating air through the Mersey tunnel system." "Incredibly these are the original fans that were first installed down here almost 100 years ago." "Each fan can move 83,000 cubic feet of air a minute safely pumping exhaust fumes from the top of the 200-foot high tower above." "Now this is a place that very few people get a chance to see." "I'm standing right at the bottom of one of the ventilation shafts." "The huge height of the tower ensures the air supply isn't contaminated by vehicle exhaust fumes from the street." "It's said that the air down here is even cleaner than the air for the people walking around in the streets of Liverpool." "Once the largest tunnel ever drilled, the road only uses the top half of the original tunnel." "Most people when they drive through the tunnel, they think they're at the bottom, but they're not." "Actually below them is this two-story high space called Central Avenue." "The lower level was designed to house a tram line, but it was never built." "Now it serves as the main air supply duct where air from the tower is blown into the road deck above." "It's pretty amazing to think that there's this space like this down beneath the road deck and I have to say, it's pretty cool to be down here." "With its revolutionary ventilation system, the Queensway tunnel provided the blueprint for all tunnel designs that followed." "The designers of the 35-mile-long Gotthard base tunnel are taking the systems pioneered at the Mersey tunnel to new heights of sophistication." "Electric trains will run through the tunnels, so they won't have to contend with exhaust gases." "But the ever present risk of fire in the tunnel requires a cutting-edge solution." "In the event of a fire, trains will either be diverted out of the affected tunnel at two crossover points or directed to one of two emergency stations." "As a train that's on fire approaches, the station's ventilation system will activate remotely via the tunnel control center." "Powerful 2-1/2 megawatt extractors above the track will suck toxic smoke fumes out of the tunnel, releasing it at the surface through an exhaust shaft 2,600 feet above." "Inlet fans will replenish the tunnel with clean air." "Each of the tunnel's six jet fans will raise the air pressure in the unaffected tunnel, keeping it free of smoke during evacuation." "This system is safer than the rest of the railway network in Switzerland." "If you are here as a passenger using the tunnel, you're safer tn haoutside." "Once complete, the Gotthard base tunnel will not only redefine the map of Europe, it will rewrite the rules of tunnel construction." "It stands as a testament to the people, past and present, who helped design and build it." "By drawing on the innovations of the past..." "Oh!" "...Adapting, improving, and making groundbreaking innovations of their own, the engineers and designers of this incredible tunnel have succeeded in making the impossible possible." "Generations of engineers wouldn't have been able to do this." "I'm very lucky to have spent 20 years of my professional life together with this project." "It's like a part of me."