1 00:00:03,367 --> 00:00:07,367 [narrator] Deep beneath the Alps, an elite team of engineers is 2 00:00:07,534 --> 00:00:10,501 embarking on an extraordinary mission. 3 00:00:10,667 --> 00:00:13,167 They are attempting to build the longest underground 4 00:00:13,334 --> 00:00:15,367 railway tunnel ever constructed. 5 00:00:16,567 --> 00:00:20,367 To succeed, they must drive giant tunnel drilling machines 6 00:00:20,534 --> 00:00:21,667 through solid mountains. 7 00:00:25,601 --> 00:00:29,701 Overcome unpredictable geology deep beneath the surface... 8 00:00:32,501 --> 00:00:33,501 Attention! 9 00:00:37,300 --> 00:00:38,667 ...and crushing pressure... 10 00:00:42,901 --> 00:00:46,901 ...to build a revolutionary rail line that will transform 11 00:00:47,067 --> 00:00:49,000 how Europe moves people and goods 12 00:00:49,167 --> 00:00:50,801 for generations to come. 13 00:00:51,901 --> 00:00:55,868 This incredible mega tunnel ranks in a league of ambitious 14 00:00:56,033 --> 00:01:00,467 new engineering wonders that are bigger, faster, 15 00:01:00,634 --> 00:01:02,567 taller, and more advanced 16 00:01:02,734 --> 00:01:05,167 than anything ever constructed before. 17 00:01:07,000 --> 00:01:11,701 This is the inside story of the extraordinary challenge of 18 00:01:11,868 --> 00:01:13,567 building these giants. 19 00:01:22,000 --> 00:01:24,000 ♪♪ 20 00:01:28,267 --> 00:01:31,667 France and Italy are two of Europe's economic powerhouses. 21 00:01:33,300 --> 00:01:36,968 Every year, over $100 billion worth of goods, 22 00:01:37,133 --> 00:01:39,667 from food to fuel, moves between them. 23 00:01:41,400 --> 00:01:43,667 But one of Europe's greatest natural barriers 24 00:01:43,834 --> 00:01:45,000 separates these two nations -- 25 00:01:48,267 --> 00:01:49,367 the Alps. 26 00:01:51,100 --> 00:01:53,868 For centuries, travelers and trade have had to 27 00:01:54,033 --> 00:01:55,667 cross the mountains the hard way -- 28 00:01:57,067 --> 00:01:59,601 through deep valleys, narrow passes, 29 00:01:59,767 --> 00:02:01,100 and winding routes. 30 00:02:03,567 --> 00:02:05,901 But now, engineers are attempting 31 00:02:06,067 --> 00:02:07,467 something extraordinary. 32 00:02:12,200 --> 00:02:14,968 A joint French and Italian operation is building 33 00:02:15,133 --> 00:02:20,300 a colossal 165-mile railway line to link Lyon in France 34 00:02:20,467 --> 00:02:21,667 with Turin in Italy. 35 00:02:23,901 --> 00:02:26,901 When complete, it could cut greenhouse gas emissions 36 00:02:27,067 --> 00:02:29,634 by over one million tons, 37 00:02:32,100 --> 00:02:35,000 and slash journey times across the mountains from almost 38 00:02:35,167 --> 00:02:37,534 four hours to under two. 39 00:02:40,000 --> 00:02:41,367 At the heart of the project 40 00:02:41,534 --> 00:02:43,367 lies its most ambitious section. 41 00:02:45,267 --> 00:02:47,267 Instead of going over the Alps, 42 00:02:47,434 --> 00:02:49,400 the engineers are digging straight through them. 43 00:02:56,701 --> 00:02:58,901 This is the Mont Cenis base tunnel, 44 00:03:00,200 --> 00:03:03,367 a vast railway tunnel being carved deep beneath the Alps. 45 00:03:07,567 --> 00:03:09,467 Stretching over 35 miles, 46 00:03:10,968 --> 00:03:13,868 it will be the longest railway tunnel in the world. 47 00:03:15,367 --> 00:03:17,667 And it must be ready by 2033. 48 00:03:19,467 --> 00:03:23,667 It's the responsibility of CEO Maurizio Bufalini to keep 49 00:03:23,834 --> 00:03:28,300 this vast international project on time and on budget. 50 00:03:30,767 --> 00:03:35,667 [Maurizio] The cost of this project is 11 billion euros. 51 00:03:36,701 --> 00:03:40,601 But it's not simply a cost, it's really an investment on 52 00:03:40,767 --> 00:03:41,901 the future of Europe. 53 00:03:42,067 --> 00:03:44,000 ♪♪ 54 00:03:45,868 --> 00:03:48,868 Halfway between Lyon and Turin, the tunnel will link 55 00:03:49,033 --> 00:03:50,567 Saint-Jean-de-Maurienne in France 56 00:03:54,467 --> 00:03:58,000 to Susa in Italy, over 35 miles away. 57 00:04:03,667 --> 00:04:07,167 Engineers are digging two enormous tubes, 58 00:04:07,334 --> 00:04:09,701 each nearly 30 feet in diameter, 59 00:04:09,868 --> 00:04:11,968 side by side, beneath the mountains. 60 00:04:13,801 --> 00:04:17,534 One carries trains toward France, the other toward Italy. 61 00:04:20,000 --> 00:04:22,968 Every 1,100 feet, passages connect the two 62 00:04:23,133 --> 00:04:26,167 tunnels to create vital escape routes in an emergency. 63 00:04:29,968 --> 00:04:33,567 Above the tunnel, engineers are also drilling four vertical 64 00:04:33,734 --> 00:04:36,467 shafts, each hundreds of feet deep, 65 00:04:36,634 --> 00:04:37,767 to help ventilate the tunnel. 66 00:04:41,868 --> 00:04:44,667 When complete, trains will race beneath the Alps 67 00:04:44,834 --> 00:04:48,100 at speeds around 125 miles per hour. 68 00:04:54,567 --> 00:04:57,601 Work on this mega-project begins in 2001. 69 00:04:59,801 --> 00:05:04,167 It takes 14 years to excavate almost 11 miles of preparatory 70 00:05:04,334 --> 00:05:07,901 tunnels to study the rock, the water, 71 00:05:08,067 --> 00:05:10,367 and the immense pressures deep beneath the Alps. 72 00:05:14,167 --> 00:05:16,367 Now, engineers are preparing to 73 00:05:16,534 --> 00:05:20,033 drive the two railway tunnels through the mountains. 74 00:05:22,501 --> 00:05:25,567 Overseeing this vast operation is Constructions Director 75 00:05:25,734 --> 00:05:26,767 Emmanuel Humbert. 76 00:05:44,100 --> 00:05:47,567 In total, the railway project requires workers to excavate 77 00:05:47,734 --> 00:05:51,400 37 million tons of rock across a 100 mile route, 78 00:05:53,567 --> 00:05:56,968 enough to fill around 6,000 Olympic swimming pools. 79 00:05:58,100 --> 00:06:01,067 This is how Emmanuel and his team will do it. 80 00:06:05,467 --> 00:06:10,267 First, engineers dig an 11-mile network of four access points 81 00:06:10,434 --> 00:06:12,300 and two tunnel portals at either end. 82 00:06:14,367 --> 00:06:16,701 They divide the excavation into sections, 83 00:06:16,868 --> 00:06:19,200 numbered from CO1 to CO9. 84 00:06:20,901 --> 00:06:23,367 This allows engineers to work from several different 85 00:06:23,534 --> 00:06:25,267 locations at once. 86 00:06:27,701 --> 00:06:31,167 Underground, they assemble eight giant tunnel boring 87 00:06:31,334 --> 00:06:33,234 machines, or TBMs. 88 00:06:35,667 --> 00:06:37,901 These launch from different points within the Alps. 89 00:06:41,567 --> 00:06:43,868 Attacking the mountain from multiple places 90 00:06:44,033 --> 00:06:46,367 helps the engineers to reduce construction time. 91 00:06:47,901 --> 00:06:50,767 Eventually, these sections will join to create 92 00:06:50,934 --> 00:06:52,267 one continuous route. 93 00:06:52,434 --> 00:06:54,367 ♪♪ 94 00:07:13,100 --> 00:07:15,467 Engineers need a mega machine to dig 95 00:07:15,634 --> 00:07:17,667 all the sections of this record-breaking tunnel. 96 00:07:22,701 --> 00:07:27,267 Viviana is a tunnel boring machine, or TBM. 97 00:07:27,434 --> 00:07:31,868 She's almost 600 feet long and weighs 2,500 tons. 98 00:07:33,100 --> 00:07:36,200 The first challenge engineers face is to get the machine onto 99 00:07:36,367 --> 00:07:38,801 the site and into the tunnel. 100 00:07:41,267 --> 00:07:44,100 A manufacturer in Germany fabricates Viviana. 101 00:07:46,567 --> 00:07:50,467 The engineers must transport the machine more than 300 miles 102 00:07:50,634 --> 00:07:52,267 from the factory to the dig site 103 00:07:52,434 --> 00:07:53,701 in Saint-Jean-de-Maurienne. 104 00:07:57,300 --> 00:07:59,968 She's too big and heavy to transport in one piece, 105 00:08:01,300 --> 00:08:03,767 so workers break her into sections. 106 00:08:05,968 --> 00:08:08,367 A fleet of low loaders transports the parts 107 00:08:08,534 --> 00:08:10,067 to the CO7 tunnel site. 108 00:08:14,601 --> 00:08:17,367 Safety vehicles shepherd the truck for this hazardous 109 00:08:17,534 --> 00:08:19,467 journey along narrow country roads. 110 00:08:24,467 --> 00:08:26,667 And through small Alpine villages 111 00:08:26,834 --> 00:08:28,567 with just inches to spare. 112 00:08:31,000 --> 00:08:33,868 Now, the engineers need to assemble Viviana. 113 00:08:35,267 --> 00:08:38,467 First, they lower each of her mega components through 114 00:08:38,634 --> 00:08:40,501 an access point into the tunnel below. 115 00:08:42,767 --> 00:08:45,868 Each one weighs an average of 66 tons. 116 00:08:52,200 --> 00:08:54,501 Next comes the assembly stage. 117 00:08:56,968 --> 00:08:59,167 At the front of the machine is the cutter head, 118 00:09:00,267 --> 00:09:03,601 a wheel that weighs roughly 330 tons 119 00:09:03,767 --> 00:09:06,968 and carries 61 disc cutters. 120 00:09:09,400 --> 00:09:12,400 This is the part of Viviana that will grind the rock to 121 00:09:12,567 --> 00:09:14,567 excavate the five and a half mile section 122 00:09:14,734 --> 00:09:16,367 of the Mont Cenis base tunnel. 123 00:09:34,667 --> 00:09:38,000 The engineers successfully assemble Viviana's critical 124 00:09:38,167 --> 00:09:39,234 front section. 125 00:09:41,000 --> 00:09:43,601 They turn the machine 90 degrees to access 126 00:09:43,767 --> 00:09:44,667 the rock face. 127 00:09:48,400 --> 00:09:50,467 It takes workers six months to 128 00:09:50,634 --> 00:09:53,167 build the huge rear section of the tunneling machine. 129 00:09:56,968 --> 00:10:00,767 Viviana is now ready to punch her way beneath the Alps. 130 00:10:15,701 --> 00:10:19,601 Engineers in France and Italy are digging the world's longest 131 00:10:19,767 --> 00:10:21,267 railway tunnel beneath the Alps. 132 00:10:23,501 --> 00:10:26,200 Their next challenge is to complete the first section of 133 00:10:26,367 --> 00:10:28,000 the over 35-mile route 134 00:10:29,200 --> 00:10:31,767 from Saint-Martin-la-Porte to La Praz. 135 00:10:33,467 --> 00:10:36,767 The nearly 600-foot-long tunnel boring machine, 136 00:10:36,934 --> 00:10:38,567 Viviana, is vital. 137 00:10:40,200 --> 00:10:43,667 The tool engineers will use to excavate the rock face is 138 00:10:43,834 --> 00:10:48,033 the 34-foot-wide cutter head at the front of the machine. 139 00:10:50,467 --> 00:10:53,767 It consists of 61 cutters made of tungsten. 140 00:10:55,701 --> 00:10:59,767 The head completes up to three rotations a minute to excavate 141 00:10:59,934 --> 00:11:01,868 2,200 tons of rock in a day. 142 00:11:03,901 --> 00:11:07,467 At its fastest, the machine can excavate nearly 50 feet of 143 00:11:07,634 --> 00:11:09,868 mountain every 24 hours. 144 00:11:12,300 --> 00:11:15,667 But as the machine drives deeper beneath the Alps, 145 00:11:15,834 --> 00:11:18,000 the team faces a dangerous challenge. 146 00:11:19,767 --> 00:11:21,667 Every foot it cuts leaves 147 00:11:21,834 --> 00:11:23,901 a stretch of excavated tunnel behind it. 148 00:11:25,367 --> 00:11:28,167 The weight of the mountains can cause the newly opened ground 149 00:11:28,334 --> 00:11:29,267 to close up. 150 00:11:30,667 --> 00:11:32,701 This movement is called convergence. 151 00:11:33,767 --> 00:11:35,801 [Emmanuel speaks] 152 00:11:50,267 --> 00:11:53,868 If the team fails to support the excavation fast enough, 153 00:11:54,033 --> 00:11:55,667 the mountain can distort the tunnel, 154 00:11:56,767 --> 00:11:59,000 drop unstable rock onto the machinery, 155 00:12:00,400 --> 00:12:02,868 or even trap the machine underground. 156 00:12:06,300 --> 00:12:07,901 This is the team's solution to 157 00:12:08,067 --> 00:12:10,234 prevent a catastrophic tunnel collapse. 158 00:12:12,667 --> 00:12:16,367 A mechanical erector arm lifts the precast concrete segments 159 00:12:16,534 --> 00:12:17,434 into place. 160 00:12:18,667 --> 00:12:21,267 Each curved segment weighs 11 tons. 161 00:12:22,367 --> 00:12:25,367 Together, the segments form a complete ring 162 00:12:25,534 --> 00:12:26,834 that supports the tunnel. 163 00:12:29,167 --> 00:12:33,467 Once the ring is complete, hydraulic rams push against it 164 00:12:33,634 --> 00:12:35,100 and drive the machine forward. 165 00:12:36,167 --> 00:12:39,000 The machine then excavates the next section of tunnel. 166 00:12:40,501 --> 00:12:43,667 Behind the shield, engineers inject grout into 167 00:12:43,834 --> 00:12:45,767 the gap between the lining and the rock. 168 00:12:47,067 --> 00:12:50,767 The grout fills the void, stabilizes the ground, 169 00:12:50,934 --> 00:12:51,901 and seals the tunnel. 170 00:13:04,567 --> 00:13:07,100 It's Guillaume Lefrere's responsibility to make sure 171 00:13:07,267 --> 00:13:09,367 the tunnel remains stable for that long. 172 00:13:43,767 --> 00:13:45,767 The machine's robotic arm delivers 173 00:13:45,934 --> 00:13:47,400 the first concrete segment. 174 00:13:50,901 --> 00:13:53,868 It must place it with millimeter accuracy. 175 00:13:56,300 --> 00:13:59,467 Small errors that accumulate over the length of the tunnel 176 00:13:59,634 --> 00:14:01,567 could create a dangerous misalignment. 177 00:14:04,801 --> 00:14:06,801 [Guillaume speaks] 178 00:14:11,467 --> 00:14:14,000 The machine's workers slot the segment into position. 179 00:14:16,000 --> 00:14:18,868 One by one, the arm lifts and places 180 00:14:19,033 --> 00:14:20,000 the remaining segments 181 00:14:21,968 --> 00:14:23,601 to create a complete ring 182 00:14:23,767 --> 00:14:25,267 around the inside of the tunnel. 183 00:14:27,667 --> 00:14:30,701 This rigid collar is strong enough to resist the weight of 184 00:14:30,868 --> 00:14:32,100 the mountain above it. 185 00:14:34,000 --> 00:14:36,767 The next challenge for the engineers is to ensure that 186 00:14:36,934 --> 00:14:39,000 Viviana is heading in the right direction. 187 00:14:41,267 --> 00:14:43,067 It's critical that she follows 188 00:14:43,234 --> 00:14:45,367 a precise route to dig her section. 189 00:14:46,901 --> 00:14:50,567 Any deviation will mean that her tunnel will not line up 190 00:14:50,734 --> 00:14:52,267 with the other tunnel sections. 191 00:14:53,567 --> 00:14:56,300 Correcting the misalignment will put the engineers 192 00:14:56,467 --> 00:14:57,400 behind schedule. 193 00:15:05,834 --> 00:15:09,667 Engineers in France and Italy are digging the world's longest 194 00:15:09,834 --> 00:15:11,367 railway tunnel beneath the Alps. 195 00:15:13,567 --> 00:15:15,601 The nearly 600-foot-long tunnel 196 00:15:15,767 --> 00:15:18,267 boring machine, Viviana, is vital. 197 00:15:19,868 --> 00:15:24,100 To keep Viviana on track, her driver, Christelle Desmons, 198 00:15:24,267 --> 00:15:26,767 relies on a special digital guidance system. 199 00:15:27,834 --> 00:15:29,834 [Christelle speaks] 200 00:15:44,100 --> 00:15:47,067 Engineers above ground use GPS to plot 201 00:15:47,234 --> 00:15:50,033 the tunnel's exact path. 202 00:15:50,200 --> 00:15:54,267 Underground, Christelle tracks Viviana's course relative to 203 00:15:54,434 --> 00:15:55,300 the planned route. 204 00:16:12,601 --> 00:16:13,934 The guidance system warns 205 00:16:14,100 --> 00:16:16,934 Christelle when Viviana drifts offline. 206 00:16:19,367 --> 00:16:22,200 Christelle then adjusts the angle of the machine to 207 00:16:22,367 --> 00:16:25,300 correct the deviation and keep the tunnel on course. 208 00:16:28,167 --> 00:16:30,167 ♪♪ 209 00:16:33,767 --> 00:16:38,367 For now, Viviana is right on track, and she continues 210 00:16:38,534 --> 00:16:41,167 tunneling towards the team digging in La Praz, 211 00:16:41,334 --> 00:16:42,667 five and a half miles away. 212 00:16:47,467 --> 00:16:49,767 To stay on schedule, the machines digging 213 00:16:49,934 --> 00:16:52,934 the 35-mile-long Mont Cenis base tunnel 214 00:16:53,100 --> 00:16:55,367 need a steady supply of concrete segments. 215 00:17:02,200 --> 00:17:04,467 The tunnel's location creates a big problem 216 00:17:04,634 --> 00:17:05,667 for the engineers. 217 00:17:07,300 --> 00:17:10,067 The nine sites above ground are isolated 218 00:17:10,234 --> 00:17:12,267 and sit in narrow alpine valleys. 219 00:17:13,567 --> 00:17:15,367 The CO7 site that supports 220 00:17:15,534 --> 00:17:18,200 the tunneling machine Viviana is no exception. 221 00:17:20,467 --> 00:17:23,367 Trucking in concrete segments will clog up the narrow 222 00:17:23,534 --> 00:17:25,601 mountain roads with traffic for a decade. 223 00:17:27,868 --> 00:17:30,734 The engineers' solution is to make what they need 224 00:17:30,901 --> 00:17:32,033 from the tunnel itself. 225 00:17:37,467 --> 00:17:41,200 Viviana excavates 2,200 tons of material a day. 226 00:18:08,000 --> 00:18:11,467 It's critical that the supply of concrete components keeps 227 00:18:11,634 --> 00:18:13,467 pace with the demand from the tunneling team. 228 00:18:17,100 --> 00:18:18,934 So the engineers build this -- 229 00:18:22,467 --> 00:18:24,400 the Illaz Transformation Plant. 230 00:18:25,868 --> 00:18:29,934 It's a huge concrete factory near the tunnel entrance that 231 00:18:30,100 --> 00:18:31,567 turns the rock that Viviana 232 00:18:31,734 --> 00:18:33,601 excavates into building materials. 233 00:18:39,367 --> 00:18:41,868 Project Director, Sébastien Paulet, 234 00:18:42,033 --> 00:18:43,200 oversees the operation. 235 00:18:59,367 --> 00:19:01,367 Once the rock arrives at the plant, 236 00:19:01,534 --> 00:19:04,267 the recycling process begins with quality control. 237 00:19:08,467 --> 00:19:12,100 The plant feeds material into powerful industrial crushers. 238 00:19:14,100 --> 00:19:17,767 These break the rock down into smaller and smaller pieces. 239 00:19:20,200 --> 00:19:23,868 These pieces then pass over a vibrating screening system 240 00:19:24,033 --> 00:19:26,501 that separate them into different grain sizes 241 00:19:26,667 --> 00:19:27,601 for different purposes. 242 00:19:43,767 --> 00:19:46,667 At every stage, machines monitor the material 243 00:19:46,834 --> 00:19:47,767 for impurities. 244 00:19:53,467 --> 00:19:56,667 An industrial washer then removes dust, clay, 245 00:19:56,834 --> 00:19:59,267 and other unwanted material from the crushed stone. 246 00:20:05,667 --> 00:20:09,367 The final product is then dried and emerges as aggregate. 247 00:20:13,567 --> 00:20:16,734 The material this factory makes is turned into concrete 248 00:20:16,901 --> 00:20:19,734 segments for Viviana to line the walls of the tunnel. 249 00:20:23,601 --> 00:20:26,367 Workers will also use it as backfill for stations 250 00:20:26,534 --> 00:20:29,033 and viaducts along the route between Turin and Lyon. 251 00:20:29,200 --> 00:20:31,100 ♪♪ 252 00:20:36,667 --> 00:20:40,067 The Mont Cenis base tunnel project aims to process over 253 00:20:40,234 --> 00:20:44,734 25 million tons of rock, and to reuse at least half of 254 00:20:44,901 --> 00:20:46,033 the excavated material. 255 00:20:47,501 --> 00:20:50,601 The project underground could slow to a crawl 256 00:20:50,767 --> 00:20:53,767 if Sébastien's plant fails to keep up with demand. 257 00:21:05,067 --> 00:21:08,868 But for now, the entire operation is on track. 258 00:21:09,033 --> 00:21:13,400 Today, the team has produced 880 tons of aggregate. 259 00:21:13,567 --> 00:21:15,501 [Sébastien speaks] 260 00:21:35,968 --> 00:21:39,367 Engineers in Italy and France are building the world's 261 00:21:39,534 --> 00:21:42,601 longest railway tunnel under the Alps. 262 00:21:45,033 --> 00:21:47,834 Punching a hole this long beneath a mountain range 263 00:21:48,000 --> 00:21:50,234 presents them with a big challenge. 264 00:21:52,667 --> 00:21:55,567 The Alps are made from 15 different types of rock, 265 00:21:57,367 --> 00:21:59,601 from hard, gneiss, and metasandstone 266 00:22:02,100 --> 00:22:04,400 to flaky layered rock called schist 267 00:22:06,467 --> 00:22:09,734 and fractured limestone that holds vast amounts of water. 268 00:22:12,100 --> 00:22:14,767 The hole a tunnel boring machine makes through gneiss 269 00:22:14,934 --> 00:22:17,100 holds its shape because of the strength of the rock. 270 00:22:18,767 --> 00:22:20,200 This makes it easy for the crew 271 00:22:20,367 --> 00:22:22,400 to reinforce the tunnel with concrete. 272 00:22:24,834 --> 00:22:27,367 But a tunnel through the wetter, less stable rock 273 00:22:27,534 --> 00:22:30,033 is more likely to contract 274 00:22:30,200 --> 00:22:32,267 as the huge weight of the mountains above 275 00:22:32,434 --> 00:22:34,601 pushes down on it. 276 00:22:37,067 --> 00:22:41,267 This creates a big problem for the engineers, as they discover 277 00:22:41,434 --> 00:22:43,167 close to the Saint-Jean-de-Maurienne 278 00:22:43,334 --> 00:22:44,767 section of the tunnel. 279 00:22:44,934 --> 00:22:48,067 [Maurizio] We have found the ground very full of water. 280 00:22:50,267 --> 00:22:55,100 And when you do the excavation, you excavate ten meters. 281 00:22:55,267 --> 00:22:58,167 In a few days, it was closing of two meters. 282 00:22:58,334 --> 00:23:00,400 It was incredible. 283 00:23:00,567 --> 00:23:03,067 If you have a situation like this with a tunnel boring 284 00:23:03,234 --> 00:23:06,033 machine, the tunnel boring machine has not the time to 285 00:23:06,200 --> 00:23:10,400 create the ring, and so it will be blocked in the mountain 286 00:23:10,567 --> 00:23:11,968 and then will die inside. 287 00:23:13,934 --> 00:23:15,667 A tunneling machine works best 288 00:23:15,834 --> 00:23:17,200 when the geology is predictable. 289 00:23:19,567 --> 00:23:21,834 When it's not, the engineers turn to 290 00:23:22,000 --> 00:23:24,734 explosives to smash big holes in the rock. 291 00:23:26,934 --> 00:23:29,167 This method is called drill and blast. 292 00:23:30,868 --> 00:23:34,367 It gives engineers more control because they can excavate 293 00:23:34,534 --> 00:23:37,567 the tunnel in short sections and inspect the ground 294 00:23:37,734 --> 00:23:38,667 after every blast. 295 00:23:43,467 --> 00:23:46,734 Drilling rigs bore dozens of holes into the rock face in 296 00:23:46,901 --> 00:23:47,901 a precise pattern. 297 00:23:50,033 --> 00:23:52,601 Engineers position each hole to control 298 00:23:52,767 --> 00:23:54,100 how the rock will fracture. 299 00:23:56,200 --> 00:24:00,300 Next, crews load the holes with measured explosive charges. 300 00:24:02,734 --> 00:24:06,100 Electronic detonators link the charges and fire them in 301 00:24:06,267 --> 00:24:07,367 a timed sequence. 302 00:24:09,834 --> 00:24:12,067 The blast then ripples through the rock 303 00:24:12,234 --> 00:24:13,400 in fractions of a second. 304 00:24:15,067 --> 00:24:18,601 The force drives forward, breaks the rock face, 305 00:24:18,767 --> 00:24:20,200 and protects the tunnel walls. 306 00:24:21,868 --> 00:24:24,167 Crews clear the rubble. 307 00:24:24,334 --> 00:24:26,467 Then, they spray shotcrete onto the walls. 308 00:24:28,100 --> 00:24:31,100 This quick-drying concrete firms the tunnel 309 00:24:31,267 --> 00:24:33,767 and stops it from contracting. 310 00:24:33,934 --> 00:24:36,834 By using this method, the team can carve out up to 311 00:24:37,000 --> 00:24:41,200 13 feet of tunnel and 880 tons of rock every day. 312 00:24:44,767 --> 00:24:48,100 Constructions Director Emmanuel Humbert oversees 313 00:24:48,267 --> 00:24:49,701 this delicate process. 314 00:24:52,167 --> 00:24:55,467 Emmanuel's team builds a digital 3D profile of 315 00:24:55,634 --> 00:24:59,300 the rock face using data from surveys and laser scanning. 316 00:25:03,667 --> 00:25:06,868 This shows precisely where the explosive charges need to 317 00:25:07,033 --> 00:25:09,567 go to ensure the rock fractures cleanly. 318 00:25:11,267 --> 00:25:15,467 A huge machine called a jumbo drills the holes in the rock. 319 00:25:17,467 --> 00:25:20,734 At the ends of the jumbo's three hydraulic arms are 320 00:25:20,901 --> 00:25:24,434 powerful drills that punch into the rock simultaneously. 321 00:25:26,868 --> 00:25:30,367 The jumbo uses the digital pattern to drill the holes to 322 00:25:30,534 --> 00:25:33,367 a precise position, angle, and depth. 323 00:25:34,868 --> 00:25:38,067 Each hole must follow the drill pattern precisely. 324 00:25:40,167 --> 00:25:42,300 Just one misaligned hole, 325 00:25:42,467 --> 00:25:45,567 and the explosion could fail to break the rock cleanly. 326 00:25:46,767 --> 00:25:48,834 [Emmanuel speaks] 327 00:26:00,601 --> 00:26:04,267 Next, workers load each hole with an explosive charge. 328 00:26:13,767 --> 00:26:15,968 Blasting the rock is a delicate 329 00:26:16,133 --> 00:26:17,767 and perilous balancing act. 330 00:26:19,167 --> 00:26:22,033 Too little power and the blast will fail to break 331 00:26:22,200 --> 00:26:23,767 the rock cleanly. 332 00:26:23,934 --> 00:26:27,400 Too much and the tunnel itself could be put at risk. 333 00:26:31,467 --> 00:26:33,567 With the charges set, the crew 334 00:26:33,734 --> 00:26:35,200 retreats to a safe distance 335 00:26:39,067 --> 00:26:40,667 and prepares for the detonation. 336 00:26:44,834 --> 00:26:45,868 Attention! 337 00:26:54,400 --> 00:26:58,300 Nelson Gomes Pina and a small team of miners assess 338 00:26:58,467 --> 00:26:59,601 the results of the blast. 339 00:27:01,968 --> 00:27:03,968 [speaks French] 340 00:27:14,868 --> 00:27:17,868 [in English] An excavator shovels the hundreds of tons of blasted 341 00:27:18,033 --> 00:27:19,667 rock into waiting dump trucks. 342 00:27:21,767 --> 00:27:24,667 These take it to the Illaz processing plant, 343 00:27:24,834 --> 00:27:27,567 where the rock is turned into aggregate to make concrete 344 00:27:27,734 --> 00:27:29,133 segments that line the tunnel. 345 00:27:31,567 --> 00:27:35,367 It takes the team two hours to clear the debris and prepare 346 00:27:35,534 --> 00:27:37,100 the face for the next cycle. 347 00:27:48,200 --> 00:27:50,267 ♪♪ 348 00:27:52,467 --> 00:27:56,000 Engineers building the world's longest railway tunnel are 349 00:27:56,167 --> 00:27:58,467 blasting their way through the rock beneath the Alps. 350 00:27:59,834 --> 00:28:01,634 Attention! 351 00:28:04,100 --> 00:28:07,767 They're constructing the over 35-mile long tunnel in separate 352 00:28:07,934 --> 00:28:10,267 sections that will join into one length. 353 00:28:13,467 --> 00:28:15,133 A team clears away the rubble 354 00:28:15,300 --> 00:28:18,267 from a controlled blast in tunnel section CO8. 355 00:28:25,200 --> 00:28:28,567 The next challenge is to make the freshly blasted tunnel safe 356 00:28:28,734 --> 00:28:31,701 for the crews that will install its concrete lining. 357 00:28:34,133 --> 00:28:37,968 The team uses a mechanical breaker to smash any dangerous 358 00:28:38,133 --> 00:28:40,267 overhanging rock left after the blast. 359 00:28:53,033 --> 00:28:55,067 [machinery beeps] 360 00:28:56,167 --> 00:28:58,267 The next task is to line the tunnel 361 00:28:58,434 --> 00:29:00,601 with a material that will stabilize it. 362 00:29:03,067 --> 00:29:05,734 The team uses a substance called shotcrete, 363 00:29:06,868 --> 00:29:10,467 a fast-setting concrete that workers fire from special hoses 364 00:29:10,634 --> 00:29:12,267 at high speeds. 365 00:29:14,734 --> 00:29:18,567 It sticks to the rock and dries quickly to form a hard 366 00:29:18,734 --> 00:29:21,501 protective shell that helps to hold the tunnel shape. 367 00:29:37,200 --> 00:29:39,501 ♪♪ 368 00:29:41,968 --> 00:29:42,968 [music ends] 369 00:29:47,133 --> 00:29:49,667 With the shotcrete dry, the tunnel is ready for 370 00:29:49,834 --> 00:29:52,033 the next stage of construction. 371 00:29:54,467 --> 00:29:58,467 It is the responsibility of Georgiana Noreanu Bocur 372 00:29:58,634 --> 00:30:00,167 to oversee the installation of 373 00:30:00,334 --> 00:30:02,367 the tunnel's permanent concrete lining. 374 00:30:04,367 --> 00:30:06,734 The shotcrete is only designed to ensure 375 00:30:06,901 --> 00:30:10,834 the short-term durability and safety whilst the works of 376 00:30:11,000 --> 00:30:12,534 excavations are carried out. 377 00:30:15,000 --> 00:30:17,367 If we don't install the permanent lining all 378 00:30:17,534 --> 00:30:20,934 around, the tunnel, yeah, might cave in at long-term. 379 00:30:25,767 --> 00:30:29,133 Georgiana's team faces a big problem. 380 00:30:29,300 --> 00:30:33,067 The extreme pressure nearly 1,500 feet beneath the Alps 381 00:30:33,234 --> 00:30:35,300 forces groundwater into the tunnel. 382 00:30:37,767 --> 00:30:41,467 The team must stop this water and make sure the tunnel is dry 383 00:30:41,634 --> 00:30:43,400 before they line the wall with concrete. 384 00:30:48,167 --> 00:30:51,601 Water is a really big problem in the tunnel because when it 385 00:30:51,767 --> 00:30:55,467 gets in contact with the concrete, it may infiltrate 386 00:30:55,634 --> 00:30:58,467 and may create, like, micro cracks, which may develop 387 00:30:58,634 --> 00:31:02,167 in time and actually damage the lifespan of the concrete. 388 00:31:04,267 --> 00:31:05,767 This is why we are installing all of 389 00:31:05,934 --> 00:31:06,868 the waterproofing layers. 390 00:31:11,467 --> 00:31:14,300 The waterproofing consists of three special sheets -- 391 00:31:15,968 --> 00:31:17,767 a membrane that repels water, 392 00:31:19,567 --> 00:31:22,167 a super strong textile that prevents punctures, 393 00:31:23,667 --> 00:31:25,400 and an inner layer that 394 00:31:25,567 --> 00:31:27,667 protects the waterproofing from jagged edges. 395 00:31:34,868 --> 00:31:37,167 Now it's time to line the tunnel with concrete. 396 00:31:46,167 --> 00:31:50,834 First, the team cuts and welds nearly 4,500 tons of steel 397 00:31:51,000 --> 00:31:53,968 rebar to make the bottom curve of the tunnel section. 398 00:31:57,868 --> 00:32:01,968 They then pour 2,825 cubic feet of concrete 399 00:32:02,133 --> 00:32:03,667 at a time into this frame. 400 00:32:07,000 --> 00:32:08,868 The steel strengthens the concrete 401 00:32:09,033 --> 00:32:10,267 and extends its lifespan. 402 00:32:16,667 --> 00:32:19,868 We need to ensure a permanent concrete lining at least 403 00:32:20,033 --> 00:32:21,367 50 centimeters thick. 404 00:32:27,300 --> 00:32:28,834 We have to build the tunnel 405 00:32:29,000 --> 00:32:31,868 basically for a lifespan of 120 years. 406 00:32:32,033 --> 00:32:34,100 So this is to ensure the long-term durability 407 00:32:34,267 --> 00:32:35,567 of the tunnel. 408 00:32:37,601 --> 00:32:40,934 It takes the workers two hours to finish the first stage. 409 00:32:45,667 --> 00:32:48,367 They then raise the height of the next concrete pours 410 00:32:49,868 --> 00:32:52,567 until the whole tunnel is lined. 411 00:32:55,000 --> 00:32:58,033 By the end of the day, Georgiana's team completes 412 00:32:58,200 --> 00:32:59,968 32 feet of tunnel. 413 00:33:02,501 --> 00:33:04,667 [Georgiana] Wonderful teamwork again today! 414 00:33:04,834 --> 00:33:06,067 We've got a big job ahead. 415 00:33:11,767 --> 00:33:14,267 So this is one concrete pour down and still a couple of more 416 00:33:14,434 --> 00:33:15,767 kilometers to go. 417 00:33:17,667 --> 00:33:21,167 But smashing through the rock creates huge clouds of dust 418 00:33:21,334 --> 00:33:24,367 and sometimes releases pockets of toxic gases. 419 00:33:25,367 --> 00:33:27,834 Prolonged exposure to these could damage the health 420 00:33:28,000 --> 00:33:29,367 of the team underground. 421 00:33:31,467 --> 00:33:35,267 The engineers' solution is to dig four ventilation shafts at 422 00:33:35,434 --> 00:33:36,767 the halfway point in the tunnel. 423 00:33:38,167 --> 00:33:40,467 Technical manager Helene Roulet 424 00:33:40,634 --> 00:33:43,100 oversees this part of the construction. 425 00:33:43,267 --> 00:33:45,167 [Helene speaks] 426 00:33:56,167 --> 00:33:59,968 Helene's team must dig two pairs of vertical shafts from 427 00:34:00,200 --> 00:34:02,133 the surface down to the tunnel below. 428 00:34:03,467 --> 00:34:04,767 [Helene speaking] 429 00:34:23,767 --> 00:34:28,834 Digging shafts this deep is a huge engineering challenge. 430 00:34:29,000 --> 00:34:32,300 This is how Helene's team will do it -- 431 00:34:34,767 --> 00:34:38,200 engineers drill a pilot hole from the surface to the tunnel, 432 00:34:38,367 --> 00:34:40,100 about 1,600 feet below. 433 00:34:41,267 --> 00:34:44,100 The hole is just 15 inches wide, 434 00:34:44,267 --> 00:34:46,767 the size of a dinner plate. 435 00:34:46,934 --> 00:34:49,367 If the drill drifts by more than nine inches, 436 00:34:49,534 --> 00:34:50,734 it could miss the tunnel. 437 00:34:53,067 --> 00:34:56,501 At the bottom, crews attach a giant cutting head 438 00:34:56,667 --> 00:34:57,601 called a reamer. 439 00:34:58,601 --> 00:35:01,567 This steel disk spans 17 feet 440 00:35:01,734 --> 00:35:04,067 and carries dozens of hardened cutters. 441 00:35:06,501 --> 00:35:09,300 A winch pulls the reamer up through the mountain. 442 00:35:11,734 --> 00:35:15,300 As it turns, the reamer chews through the rock and opens 443 00:35:15,467 --> 00:35:17,267 a 17-foot ventilation shaft. 444 00:35:17,434 --> 00:35:19,367 ♪♪ 445 00:35:24,667 --> 00:35:27,367 The team positions the drill, 446 00:35:27,534 --> 00:35:29,300 and it begins boring the pilot hole. 447 00:35:35,567 --> 00:35:39,167 Its target is the tunnel about 1,600 feet below. 448 00:35:46,300 --> 00:35:49,467 After six weeks, the drill bit breaks through 449 00:35:49,634 --> 00:35:50,567 the tunnel's roof. 450 00:36:03,968 --> 00:36:07,667 Next, a team inside the tunnel constructs the reamer 451 00:36:07,834 --> 00:36:10,000 from 32 special discs. 452 00:36:12,467 --> 00:36:16,300 The team above ground spins these cutters and pulls them up 453 00:36:16,467 --> 00:36:19,667 to bore out a huge 17 foot diameter shaft. 454 00:36:24,767 --> 00:36:27,868 Helene's team constantly monitors the reamer 455 00:36:28,033 --> 00:36:30,868 to make sure it cuts the rock cleanly and efficiently. 456 00:36:32,367 --> 00:36:35,734 It takes the team two and a half months to excavate 457 00:36:35,901 --> 00:36:38,534 the over 1,600 feet to the surface. 458 00:36:41,000 --> 00:36:43,367 The engineers' next challenge 459 00:36:43,534 --> 00:36:45,367 is to secure the walls of the shaft. 460 00:36:46,667 --> 00:36:50,367 Loose rock could fall and injure the workers below, 461 00:36:50,534 --> 00:36:52,167 so they must find a solution. 462 00:37:00,267 --> 00:37:04,267 Engineers in France and Italy are digging the world's longest 463 00:37:04,434 --> 00:37:06,534 railway tunnel beneath the Alps. 464 00:37:08,968 --> 00:37:13,300 Their next challenge is to secure the walls to the shaft. 465 00:37:15,734 --> 00:37:18,601 Loose rock could fall and injure the workers below. 466 00:37:20,734 --> 00:37:23,868 Their solution is to spray shotcrete onto the surface of 467 00:37:24,033 --> 00:37:26,133 the shaft to firm it up. 468 00:37:28,601 --> 00:37:31,467 Dangling a human on a rope with a shotcrete hose is 469 00:37:31,634 --> 00:37:33,801 unsafe and impractical, 470 00:37:36,234 --> 00:37:39,100 so Helene's team uses this special robot. 471 00:37:41,133 --> 00:37:44,601 Today, the engineers are firing it up for the first time. 472 00:38:08,567 --> 00:38:11,100 Workers connect the shotcrete pipe to the robot 473 00:38:13,400 --> 00:38:14,667 and lower it into the hole. 474 00:38:21,100 --> 00:38:24,367 The robot's pilot deploys its four legs to brace it 475 00:38:24,534 --> 00:38:25,767 against the wall of the shaft. 476 00:38:29,567 --> 00:38:31,467 [worker] OK. Down. 477 00:38:32,601 --> 00:38:34,400 [machinery honks] 478 00:38:37,934 --> 00:38:39,167 The robot gets to work. 479 00:38:45,834 --> 00:38:48,968 The robot's nozzle sprays an even coat of shotcrete onto 480 00:38:49,133 --> 00:38:50,334 the rock as it descends. 481 00:38:57,968 --> 00:39:02,334 When the robot completes 490 feet of shaft, workers install 482 00:39:02,501 --> 00:39:06,901 super strong metal ribs to reinforce the shotcreted walls. 483 00:39:09,334 --> 00:39:12,767 The ribs form a shell that strengthens the unstable 484 00:39:12,934 --> 00:39:13,934 sections of the shaft. 485 00:39:16,234 --> 00:39:18,667 It allows crews to stabilize the wall 486 00:39:18,834 --> 00:39:20,767 before they install the permanent lining. 487 00:39:22,767 --> 00:39:26,734 It takes Helene's team and the robot six months to 488 00:39:26,901 --> 00:39:29,667 shotcrete and reinforce the first shaft. 489 00:39:44,167 --> 00:39:47,400 Once all four shafts are complete, they will supply 490 00:39:47,567 --> 00:39:50,467 fresh air for the crews working deep beneath the Alps. 491 00:39:55,934 --> 00:39:58,467 And when the tunnel is finished, they will become 492 00:39:58,634 --> 00:40:01,267 vital access points to rescue passengers 493 00:40:01,434 --> 00:40:02,567 in the event of an emergency. 494 00:40:21,868 --> 00:40:24,968 The Mont Cenis base tunnel is one of the most ambitious 495 00:40:25,133 --> 00:40:27,367 engineering projects ever attempted. 496 00:40:29,834 --> 00:40:32,601 Foot by foot, the teams building it are 497 00:40:32,767 --> 00:40:34,767 getting closer to completing the longest 498 00:40:34,934 --> 00:40:36,767 railway tunnel in the world. 499 00:40:38,767 --> 00:40:41,968 You can see the tunnel and the permanent works growing 500 00:40:42,133 --> 00:40:43,467 under your eyes. 501 00:40:45,934 --> 00:40:49,567 To see the results of your own work every day, it's amazing. 502 00:40:51,133 --> 00:40:54,767 From the 2030s, high speed trains will use it to race 503 00:40:54,934 --> 00:40:57,367 between Lyon and Turin in a fraction 504 00:40:57,534 --> 00:40:58,667 of the time it takes today. 505 00:41:02,567 --> 00:41:06,667 But this is not only for people today. 506 00:41:06,834 --> 00:41:12,167 This is really an opportunity, a big opportunity for our sons 507 00:41:12,334 --> 00:41:14,667 and daughters in the future. 508 00:41:14,834 --> 00:41:18,567 These huge peaks divided Italy and France for centuries. 509 00:41:19,601 --> 00:41:24,067 Now, engineers are punching a new path under them that 510 00:41:24,234 --> 00:41:26,367 brings Europe closer together.