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Getting excited about engineering



My father gets very excited about engineering.


To mark the occasion of my very first hangover, after too much Strongbow on a Welsh campsite aged 13, my father decided to take us to Dinorwig, a hydroelectric power station. A better place to spend a hungover day I can barely imagine. “THE POWER OF WALES!” boomed the enthusiastic voice-over, as we were led through a dark cave full of clunking machinery. My head pounded. I like to think I was the kind of accommodating daughter who did a good job of feigning interest in my father's hydro-electric whims, despite aforesaid throbbing brain, but the annals of family history would suggest the opposite. It seems that his dreams of spawning a budding little engineer daughter were going to be dashed after all.


Nowadays, when my father comes to visit me in Germany, he is forced to nurse his Weissbier hangovers with long classical music concerts, an activity which excites him about as much as hydroelectric power stations excite me ( ahh the sweet taste of revenge! ) But as he often points out, the seats are very comfortable and as long as the music isn’t too loud, its a great place for a nap.


So I thought I’d take a foray into his world. I set him the challenge of choosing his favourite engineering projects, and explaining why they interest him. Some background: my father David is a civil engineer and has worked for 40 years in the construction industry, mainly in England but also for a short period in Kenya and Somalia.



So Dad, what drew you to a career in civil engineering? What do you find most fascinating about engineering?


I find civil engineering the most exciting type of engineering. One of the great things about civil engineering is that the projects are big, they’re in distant places, and they last for three years or less. This means you move around a lot, you get a lot of variation. One minute it's a bridge, next minute it's a water treatment works, or a school, a house, a shop - all sorts of different things. Because you’re doing jobs that only last a maximum of three years, you end up with many different friends. Each time you have a new team, so it's much more varied. I think that building is a good way of having a varied life.


What have your criteria been, as you’ve been choosing your favourite engineering projects?


Magnitude, and decision making. The lengths people went to in the past to create these fantastic structures. Nowadays everything has to be economically justifiable, but looking at these 6 examples, that definitely wasn't the case back in the day!



And here they are, the top 6 feats of civil engineering, as chosen by David De Butts...



Stonehenge


British cultural icon and UNESCO World Heritage Site, Stonehenge is a prehistoric monument in Wiltshire, consisting of a ring of standing stones.




Stonehenge was built about 5 thousand years ago, between 3000 and 2000 BC, when the population of the UK was probably about a million. The construction of Stonehenge would have been extremely labour-intensive, at a time when a lot of manpower was needed harvesting crops. It shows the power of religion to get people to perform remarkable deeds - things that seem totally inexplicable to us nowadays.


Stonehenge is made of two types of stone; Sarsen stones ( about 25 tons each ) which came from 20 miles away, and Blue stones ( about 3 tons each ) which were brought all the way from Wales, approximately 140 miles away. At that time, there were obviously no hard roads and no wheels, so the stones would have had to be moved using logs as rollers, or wooden sleds dragged over the ground. The ground would have been soft which would have made this even harder. The blue stones must have been cut out of the mountain with very basic tools ( probably just bits of rock ). They had to be taken either across the Severn estuary in a boat or dragged by a longer route over land. Once the stones had been transported to the site, they had to be shaped, which was done using other small stones as hand tools.


It's been recently discovered that the smaller blue stones had already been erected in another stone circle in Wales for the preceding 400 years, before being moved to Stonehenge. The people had been displaced by invaders and had to migrate, taking the stones with them. It is incredible to consider the fact that they chose to take a set of 50 stone monuments with them, weighing 3 tons each!




The Pyramids of Giza


Similar to Stonehenge, the sheer size of the job of making these pyramids is mind boggling! Built in approximately 2500 BC, the pyramids were made from stone that had been quarried upstream, approximately 500 miles away.


The biggest pyramid has a base of 230m by 230m and is 147m high. With an overall volume of 2.6m³, it is 20 times the volume of Durham cathedral ie. Durham cathedral would fit into it 20 times! It is made from 2.3 million stones, each weighing about 2.5 tonnes. It took approximately 20 years to build, with a labour force of between 20 to 100 thousand men ( there seems to be some debate about the size of the labour force). Each stone had to be cut out of the mountain side, and then transported by boat 500 miles down the Nile, and then 5 miles overland to Giza on rollers. Once on site, the stones were put into position by rolling them up a temporary embankment built against the side of the pyramid.


If we were to build the pyramids today, it would cost £25 billion, by my calculations. It is utterly amazing that a single man - the Pharaoh - could think the creation of his tomb was worth this much national effort! If we are to presume that the population of Egypt was 3 million at the time, the Pharaoh was diverting about 2% of the population (6% of working age manpower) to this task.




Durham Cathedral


This is more of a personal choice - I studied at Durham university and could see the cathedral from my bedroom window.


It was built in about 1100AD, and again, I have chosen it for the amazing effort put into its creation. It is situated on top of a hill, which lies in a bend in the river, in an area with quite a limited population. It is different to the above two items ( Stonehenge and the Pyramids of Giza ) in that it was built quite high up, and therefore the stones all had to be raised into position somehow - before the days of cranes, reliable ropes, proper scaffolding and proper stone-working tools. Cathedrals involve very intricate stone work, which would have been very skilful, costly and time consuming. If we were to build Durham cathedral today, it would cost at least £250m.


Durham cathedral took 40 years to build. By my calculations, the volume of the stone used to build the cathedral was about 40,000m3, weighing about 90,000 tonnes, and there must be another 10,000m3 of foundations. The material had to be cut out of the mountain and transported to site ( but at least, unlike during the building of Stonehenge and the Pyramids of Giza, by 1100 AD they would have had wheels and carts, and tools were a bit more sophisticated ). The main achievement was in lifting all of this stone up to this precarious height, using unreliable rope and very dodgy timber derricks on timber scaffolding. It is not clear how big the labour force was, nor how many deaths there were during the building of the cathedral. Durham is very cold in winter and stone is slippery when wet, so it's safe to assume there were more than a handful.


As an aside: Durham cathedral is just one of the 40 cathedrals and 1500 castles built in a period of 400 years ( from 1000 to 1400AD ) at a time when the population of the UK was an average of about 3 million. On top of this, about 5000 other smaller churches were built during this time. By my calculations, this would have cost £67 billion in today's money, paid for presumably by the Kings, the Lords, and the Church. Even if the labour force weren't paid, they still needed to be housed and fed. The sheer cost of all this is remarkable!




Pont du Gard


The Pont du Gard aqueduct was built in approximately 20 BC and spans a valley of about 275 min width, at a height 49 m from the bottom of the valley. It is just one part of a 50km water way, transporting water from Uzes to Nimes. The Romans went to all the effort of building this aqueduct, just to provide a water supply to the city of Nimes, which was then home to a mere 60,000 people. An astonishing effort!


It is a very impressive structure made of stone, and somehow did not leak, due to the Roman version of concrete. It contains 50,000 tonnes of stone, and took 1000 men 5 years to build - '5000 man years' - which at today's prices would cost £125m! Would anyone nowadays spend that much money to supply such a small town with water? The mind boggles as to why they didn't rebuild the town elsewhere, in a place with better access to water.




Empire state building


Though this is no longer the highest skyscraper - a mere 102 storeys compared to Dubai's Burj Khalifa tower that boasts 163 storeys - it is certainly the most famous. To me, the most amazing feature of the Empire State Building is how quickly it was built. Design started in 1929, construction started 8 months later, and it was completed and opened for business in May 1931 - 410 days from the start of laying foundations to the completion date. This means they constructed 3 storeys per week. They had much slower cranes at their disposal as we do nowadays, and crane time is the critical issue in building a tower like this. Just for comparison's sake, I worked on the construction of the NatWest Tower in London, and that took 8 years from start to finish - embarrassing really!


We're all familiar with the photos of construction workers eating their packed lunches whilst sitting on precariously high beams during the construction of the Empire State Building, but astoundingly there were only 5 deaths during construction. The building of the World Trade Centre, in the late 60's, involved 60 deaths.





The Mulberry Harbours


The Mulberry Harbours demonstrate the fantastic decision making of Churchill’s war cabinet. These temporary harbours were built at an enormous expense, to be used to deliver

supplies during the invasion of Normandy. Churchill came up with the idea of a floating harbour in May 1942.



The idea was to build a harbour the size of Dover, float it over to France and sink it into the sea bed, such that it would be a suitable pier to unload provisions directly off the ships, in the run up to the invasion. The prototypes were tested in Scotland in January 1943, construction began in August of the same year, and the harbours were ready to be taken across the channel by June 1944.


There were two harbours, each approximately the size of Dover, named Mulberry A ( for the Americans ) and B ( for the British and Canadians ). Each harbour consisted of outer steel breakwaters, inner concrete breakwaters, scuttled old ships (code-named 'Gooseberries' ), and steel jetties (code-named 'Whales' ), spanning over pontoons (code-named 'Beetles' ). The total length of these floating roadways was 16km. Each jetty went out about 2.5 km into the sea.


The materials used to build just the Phoenixes comprised approximately 600,000 tons ( = 250,000m3) of concrete and 31,000 tons of steel. The labour force peaked at 45,000 men over the 6 month period it took to build them. All the above was built secretly in the Clyde and Thames estuary and then tugged over to France starting on 4 June ( at 4 Knots = 5mph). This would have been about £200m in today’s money - all for something that would be used for only about 6 months!


One of the two Harbours, the American Mulberry A, was destroyed during a storm. Mulberry B survived and was used for the next 6 months, and was involved in the unloading of approximately 2 million troops, 500,000 vehicles and 4 million tons of materials. The Mulberry harbours must rank as the most expensive piece of short term ‘consumable’ construction ever. I think the remains are still there and are probably a bit of an eyesore.


For me, it is incredible that such a massive building project could have been conceived and carried out so quickly. It takes a huge amount of personal courage, self confidence and imagination to instruct such a massively expensive and labour-consuming project; all this to provide a harbour to be used for really quite a short period.



So there you have it, the 6 feats of engineering. And, much to my dismay, the Dinorwig hydro-electric power station didn't even make the cut!



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