Tugendag waren er alleen twee slijts op de college rama, maar we hebben het al gezegd dat de hele recordering nog steeds op de machine is, zodat ze het op de college rama gaan doen. De recovering rate is 99 procent, dus dat is waarschijnlijk oké. De vorige week hadden we over de zandkuttingen, hoor jij het? Ja, ik hoor het. Oké. Dus we hebben gevoeligd dat je een zandkutting hebt voordat je een zand krijgt, dan krijg je de dilatatie en de perusite is increasing, omdat de perusite in de water in de schierzone gevolgd is, en water wordt alleen gevolgd als je een verschillende pressie hebt. Sinds de buitenste pressie, waarom we het generaal heen, de hydrostatische pressie, zal het niet veranderen. Het enige wat dat kan veranderen is de pressie tussen de partijen, dus de deurpressie. En dat is wat er gebeurt. De deurpressie heeft een limitatie en deze limitatie is als de onderpressie in de deurpressie de watervapere pressie reacht, omdat op dat moment water begint te koeken, en de pressie kan niet meer veranderen. Sinds de, voor normaal temperaties, laten we zeggen 10 graden, deze watervapere pressie is gewoon 0.01 bar, die is 1 procent van een bar, we consideren het 0. Dus in normaal calculaties, we consideren dat de limitatie de absolute 0 pressie is. Niet 0.01, maar absolute 0, omdat de verschil is gewoon 1 procent. In general met soilkutting, of met alles wat het moet doen met soilmechanen, je moet consideren dat de curatie van de soilmechanische parameters niet te hoog is. Dus als je over een angle van internaal friktie gaat, misschien in een laboratie, je kunt het in één graden determineren, maar als je kijkt naar samples van real-life, in c2-samples zoals we zeen, ja, misschien is het 2 of 3 graden.  Nou, als je een error met een factor 2 hebt, de krachten zijn twee keer te hoog of twee keer te hoog.  Dat betekent dat als we de 1% van de waterfaperpressie neglecten, dat is een curatie van 1% en het is echt neglectabel als je met de curatie in de soilmechanische parameters hebt. Dus dat is waarom we zeggen, oké, we neglecten, het maakt alle equaties een beetje meer simpel. Oké, wat hebben we? We wilden de poor pressures calculeren en dit betekent dat in dit gebied je een bepaalde flow van twee plekken, van de bovenste en de bovenste water moet bepaalden in dat gebied, want dat is waar je de perusite increasing hebt. Dit betekent dan weer hoe de water kan bepaalden van vier directies, maar in de realiteit op één punt van de schereplijn de water kan alleen van twee directies komen, niet van vier directies. Later zal ik je laten zien een method waar eigenlijk ik de watervloven van vier directies laat zijn. De method werkt goed, maar is scientifically incorrect. Maar dat gebeurt meer in de signaal dat je een calculatie method hebt die goede resultaten geeft, maar het betekent niet, het is altijd scientifically 100 procent. Maar ik zal je later laten zien. We hebben een mesh nodig, dit was de koortsmes, dit was de fine mesh, de finer de mesh, de meer accurate de calculatie, maar ook de langere calculatie tijd voor de computer. En nu is dat niet echt een probleem, maar ik denk dat je elke keer een uur achter je laptop voordat een calculatie is bepaald en als er een mogelijkheid is om het in vijf minuten te doen, zou je de vijf minuten prefereren, omdat je in één dag meer calculatie doet. In die dagen was het een bedoel van geld en dus als we de mesh koortsmes hadden, was het te makkelijker. Maar nogmaals, je calculaties moeten accurate genoemd zijn. Dit was de resultaten, de potentiële lijnen, waar de grootste onderpressing in dit gebied is, dichtbij de etch van de blad en op de scherplijn. Dit geeft dezelfde foto, maar dan in kleur. En ik heb deze foto gekregen die de flowlijnen geeft. Dus hier zie je dat in dit hele gebied er hardly is niets te verblijven, maar in dit gebied is dit zoals een flowlijn. De division tussen twee kleuren is een flowlijn. Hier heb je flowlijnen en equipotentiële lijnen, samen. Nu hebben we een aantal issues in de equations die we gebruiken. We hebben de hoge forces, de horizontale, de verticale forces, we kunnen ze calculeren, maar er was nog een aantal in die equations. En die een aantal was de scherplijn, de aantal van de scherplijn. Dus, in feite, geïquivalent aan de derivaties die ik heb al gezien, van actieve en passieve scherplijn waar de beta ook de aantal was, en we hadden de beta analitisch opgelaten. In dit geval hebben we ook de beta te vinden, maar de equations zijn zo complicat dat je het niet analytisch kunt doen. Een reden is dat de equations complicat zijn.  Dus, eigenlijk, is het mogelijk om analytisch te zorgen in welke beta de kleinste force zal resultaten. Dus, wat doen we? In ieder geval doen we een aantal calculaties en dragen de forces als een functie van dit scherengel. Dus hier zie je de scherengel van 15 graden tot 45 graden. Dit is gewoon voor het examen. Hier zie je alpha is 60 graden, dus dat is een 60 graden blade. En dan calculate ik de horizontale force, die is de lage lijn en de totale force, om te zien of het een grote verschil zou maken. Maar als je de principale energie gebruikt, moet je alleen de horizontale force nodig zijn, omdat energie, je kan het van de kracht dragen. Nou, kracht is de kracht x velociteit, maar de kracht moet in de richting van de velociteit zijn. Als het perpendicular is, kan het niet aan de kracht contributeren. Sinds we over een horizontale scherengel, dat betekent dat we de horizontale force nodig zijn om de kracht te krijgen. En dan kun je het van tijd dragen en je hebt energie. Een multiplie van tijd en dan heb je energie. Dus eigenlijk moeten we de onderste lijn van de twee die de horizontale force is en kijken waar is die force op de minima, omdat waar die force op de minima is, dat is waarschijnlijk wat natuur zal doen. Het is nooit een garantie, maar vaak is natuur laag en natuur wil niet meer energie spenden dan nodig zijn. Dus based op dat principale, het is een beetje een filosofische principale, we vinden de beta. Dan kun je het voor de 60-degree blade zien. In fact, de punt waar je de minima voor beide forces hebt, totale force en horizontale force, is bijna bij dezelfde beta en ja, het zou zijn als je er op 20 graden kijkt. Dan kun je naar de 45-degree. Je kunt de verschil zien tussen horizontale en verticale force is een beetje groter, niet veel, maar je kunt ook zien dat de punt waar je de minima vindt gevolgd is. Nou, wat zou het zijn, iets zoals 27, 28 graden. En dan kun je naar de 30-degree blade zien. Je kunt zien dat de verschil tussen de minima is een beetje groter. Nu, ja, waar is deze minima gewoon bijna 30 graden. Dus een simpel rule van de temp based on this is that for a 60-degree blade the shear angle is between 15 and 20 degrees, then if you go to the 45, it's between 25 and 30 degrees, and usually for a 30-degree blade it's around 30 degrees. So if the blade angle decreases, the shear angle increases. And I also made a drawing of the lines for the 15-degree blade, which is a very unpractical blade, but we did tests with such blades and you can see that you are above 35 degrees. So the tendency of an increasing shear angle with a decreasing blade angle is valid. Why is a 15-degree blade not practical? Well, if you have a blade like this, 15 degrees is very flat, and the blade has a point, it means an edge, it means the edge will become very sharp. And if you would use such a blade in reality and you just hit one piece of gravel, the blade is broken because you can't make it strong enough. That's why in general in dredging, if you look at a cutterhead, I would say the blade angles they use are between 50 and 60 degrees. So they are not too small. It has a number of reasons, so one of the reasons is that a very small blade angle makes it very vulnerable. And in dredging, you can say I'm dredging sand or clay, there will always be some gravel somewhere. You will always hit those stones. So it has to be strong enough. But the second reason is that in a cutterhead you are rotating, that means at the bottom of your blade you get wear. And if you have a very flat blade, that also means the wear surface at the bottom will also become very big. In the case you have a lot of wear, your forces increase dramatically and it won't work. If I have a much steeper blade, then also the wear flat is much smaller, so the effect of wear is much smaller. The influence of wear. So how do you determine the influence of wear? In fact this is about the influence of wear on the pore pressures. If theoretically you have a blade with a very sharp edge, that means the water in the back of the blade reaches the edge of the blade. That also means that theoretically the pressure at the point, at the edge of the blade is zero, is hydrostatic. But hydrostatic we call it zero in this respect. You cannot have under pressure at a point where you also have hydrostatic pressure. So that reduces the pressures from the calculations dramatically. We know that in reality you always have some wear, but also that during the cutting process the scent is compacted a little bit. Behind the blade it will move up a little bit and the result is that the water behind the blade can never reach the edge of the blade. To test that we made blades with a wear flat, a horizontal piece behind the edge of the blade and determine the pore pressures. Well, this is the pressure in the shear plane, the average pressure. This is the average pressure on the blade and the W is the length of the wear flat and HI was the thickness of the layer cut. And what do you see that if you increase the size of the wear flat you get, let's say asymptotically to a certain stable situation. And that's what we choose for the size of this wear flat because you like it if it's reproducible and you could say, maybe this under pressure is a little bit too high. Well, the minimum is here so it's not really too high. But it's better if you overestimate the forces a little bit than when you underestimate because if they design a project based on forces that are too low you may damage your equipment. So based on that philosophy we said it's better to be a little bit too high than too low. Then you get the situation of permeability for those calculations. We have the sand before it passes the shear plane which is still the city sand with a low permeability. Then when the sand is sheering the particles roll over each other the porosity is increasing so also the permeability is increasing. But how to deal with that in such a finite element program. Well, the program we had at that time it's still at the university could deal with that you can make two areas with different permeabilities en we looked at the influence of the ratio between those permeabilities on the cutting force. Well, the ratio here you can see the K i is the permeability of the sand in city so before sheering and the K max is the permeability after sheering and you can see that if this ratio is increasing the force is decreasing. Why is that? Well, the K i is fixed because that's the permeability you have from the sand. If the permeability K max is decreasing is getting smaller this axis goes to the right but if that permeability is getting smaller the force is also getting smaller but if you take the reverse of this curve here you see it's a nice straight line and based on that straight line we found that almost exactly you can just take the K i plus the K max and divide it by two and use that permeability in your equations and just take the average of the two permeabilities. Last week I think we stopped with those equations we already looked at this so you had the C1 which was the result of the finite element calculation plus all the signs and cosines that are in the equation including the beta where the cutting forces are at the minimum Rho times G I told you normally I use 10 for that combination but if you put it in a computer program just do it as accurate as possible Vc was the cutting velocity so in meters per second H i the thickness of the layer you are cutting and it was squared because on one hand the pore pressures will be proportional to the layer the thickness of the layer could if it's two times as thick the pore pressures will be doubled but since force is the integral of the pore pressures you get a second time this layer thickness and that's why it's squared B was the width of the blade E was the dilatation so the increase of the volume of the sand with a value similarly I choose something like 0.1, 0.2 in that range but if you know the exact numbers of the porosities you can calculate it but if I don't I have to make an estimate Nkm is that average permeability so it's just the average of the permeability before shearing and after shearing for the Fv you get the same reasoning the only difference is you have a C2 now if you don't know anything about the sand you should make a what I call an educated guess and that would be that C1 is 0.5 and C2 is 0 and that means you don't have a vertical force then in the cavitating equations the water starts cooking in the pores you have a D1 the educated guess for D1 is 5 so 10 times C1 but it's 5 but because the equation is completely different you cannot compare C1 and D1 again the density of water times the G which we estimate 10 between brackets Z plus 10 Z is the water depth and the 10 is because of atmospheric pressure because rho times G times 10 is exactly 100 kPa which is 1 bar so the 10 is just the atmospheric pressure and then for each 10 meters of water depth you can add a 10 again the HI, the layer thickness why is it not squared here well the pressure is a constant once you are cavitating the pressure is a constant and the pressure doesn't depend on the layer thickness anymore so the only reason I have an H is because I have to integrate that pressure over the layer thickness and that's when I get one H in this equation and then you see the B, the width of the blade which makes sense the blade has a width which is 2 times probably the force will be 2 times it's not 100% because you have some side effects but in the 2 day, 2D situation if you make those 2 equations equal you get an equation like this and if this equation is 1 you are at the transition between the noncavitating and the cavitating process if it's 1, it's just making the 2 equations equal we talked about cavitation cavitation, if it occurs it will start in the shear plane and in that shear plane this is the area where you saw on previous pictures that we had the biggest under pressures where you have the biggest under pressures cavitation will start but cavitation means the increase of porosity has been filled with vapor bubbles not with water so during the process it will not just disappear you need water to fill up that volume so the sand is moving like this over the blade on this side water is flowing to that cavitation area filling up the pores with water and it takes a while actually before the cavitation has disappeared the cavitation can also occur here before the shear plane just because that area is catching water from the surroundings it could already start a little bit sooner if you measure here I show you the points where we had pressure transducers in the blade so we call it differential pressure transducers we can measure the pore pressure in the sand not the pressure of the sand of the particles just the pore pressure and as long as you have this cavitation spot in front of your blade measure a high under pressure and then where the cavitation spot has disappeared the under pressure will drop so you get something like this anyway that's what we would expect this shows again where did we put the pressure transducers because we already expected that near the edge of the blade there will be high gradients of the pressure while if you go to the back of the blade the change of the pressure is much less so we like to put the transducers as close as we could to the edge but you can see in this area because there you have the edge of the blade you cannot really put those transducers just no space why does it look the way it looks well in fact the actual pressure transducer was put behind the blade when the sand is moving on the blade you get a lot of wear so in fact what I'm telling you is a little bit how to do such an experiment so if I would put this pressure transducer in the blade after one test no more transducer because the sand would wear it off and it would be so damaged you can't use it again ok so what to do so we decided we make holes but if you just make a hole in the blade the hole will be filled up with sand and then what you like to keep it clean so we decided we make small pills like aspirins to put in front but those pills have to be on one hand they have to be very hard because they have to resist the wear of the sand on the other hand they have to be completely permeable because you want to measure all the changes in the pressure in the water en if those pills are not permeable then the pressure transducer will not measure anything now the problem is if you make those pills so we found the right material to make those pills you make aspirins in fact they are full of air and if you just put them in and then put water on top the air is still in those small pills because why would it go out that means air is very compressible so air in such a small pill would behave like what we call a low pass filter and filter out all the high frequency changes in the pressure you wouldn't measure a thing only over longer periods of if there are pressure difference you could measure something so what we did we made a lot of those pills we borrowed a vacuum tank in one of the other departments put them in a glass of water and put absolute vacuum in that vacuum tank so almost zero bar absolute pressure in the vacuum tank and then you can see all the air go out and we left it there for a week and then after a week you could assume all the air was out of those pills but you have to keep them underwater you cannot take them out and put them in the test facility because there will be air in again so we had to take the glass of water with those pills step with a wetsuit step in the laboratory in the tank with water pictures of that and put the glass underwater taking care those pills would never be in contact with air otherwise it won't work well that was a lot of work but it worked now first if you look at the under pressures based on those finite element calculations here you see the blade with the locations of the transducers and A B is the shear plane so A was the edge of the blade and B was where the shear plane reaches the surface well it's logic that at the point where the shear plane reaches the surface the pressure is zero then it's increasing and near the edge of the blade you could have a maximum although it doesn't have to be a full maximum as you can see here and in fact at the blade we used that wear surface to take wear and other effects into account then on the blade you can see that in fact just behind the edge of the blade you find the maximum but it completely depends on the blade angle and the layer thickness and so on and then over the blade you see a drop to zero because at the end of the blade it's in contact with water with hydrostatic pressure so the pressure is zero so this is what we calculated and then you like to know does it really happen but before I show you some data from the laboratory the method which is not scientifically correct but which works very well in fact some students did whole master degree assignments with this method to solve certain problems and they actually solved it well this method we call the parallel resistor method I don't think in soil mechanics you will ever get it but it works very well you can say if I have a point on the shear plane then the water could flow from four directions theoretically so here this is direction one direction two, direction three direction four of each direction I can determine the length for example I can say this is a circle segment so if I know the location on the shear plane I can calculate the length of that circle segment here you have a circle segment plus a straight line here you also have two circle segments plus here a piece of straight line so it's a little bit engineering intuition how to implement the method but this is the way I did it now the resistance of one line so the water flow over one line is the length of that line divided by the permeability so if you take the length of a flow line divided by the permeability it gives you a resistance from electronics or electrical engineering so if you have parallel resistors there is a rule how to determine the total resistance of a number of parallel resistors in fact the one divided by the total resistance equals one divided by the first resistance plus one divided by the second resistance et cetera et cetera so this is the way how to determine the total resistance and in fact for each line you know the S divided by K because you know in which area you are before shearing or after shearing so you know the K value and you have to make an estimate for the length I use circle segments but if you say I want to make it more fancy the difference is not very much if you choose a little bit different approach the values will almost be the same then if I know this resistance the under pressure at that point on the shear plane you can calculate with this equation so in fact the density of water G cutting velocity E and the sign of beta so basically this is a constant and then what I do I divide the shear plane in let's say 100 steps, 100 small parts and on each part I determine this under pressure that way I get a nice curve of the under pressure over the whole shear plane I can integrate it and that gives me the average under pressure on the shear plane another advantage of this is that for each point I can check whether I exceed the water vapor pressure and if I do I can limit the outcome to the water vapor pressure so the transition between no cavitation and cavitation can be determined very smoothly using this method I just want to show you the method why did some students use it well we had students who wanted to investigate if you have the drag head of a hopper dredge and you have those teeth IHC not so long ago a couple of years ago they put water jets inside the teeth in order to compensate for the under pressure in the sand they said if we can blow water into the sand before it starts dilatating we don't have those under pressures and they call it actually the dragon head and the student wanted to calculate how does it work well with this method you are more flexible in determining under pressures because everywhere you have the over pressure of the water jet you don't have under pressure so you can define that they actually graduated and what they calculated matched reality in fact I tuned this method on the finite element program the finite element method and the difference is just a few percent so and this I can put in any computer program and I do not have to wait until the finite element program has finished it's like 20 lines of code in a computer program and you can use it for everything and then if the accuracy is a few percent that's good enough this picture you already saw when I discussed soil mechanics I think what is it well in order to predict cutting forces very often what you have is SPT values and things like that not although here in Holland we have good laboratories here you have somewhere here you have the old soil mechanics laboratory and you have the deltares and so on and they can do sophisticated tests but that's not everywhere in the world so one reason is it's not always available so for example you have a project on Borneo do you think somewhere in Borneo they have a very sophisticated soil mechanics laboratory probably not still you have to do a project there and you like to know something about the soil so you can do SPT you can do CPT but usually it's tests that you can do locally if you want to know more about the material you have to send it by plane to a good laboratory and wait for the results well what does this picture show you here you have SPT value here you have relative density relative density was if it's zero it means you have the highest porosity of your sand if it's 100 percent you have the lowest porosity of your sand so you can see if the porosity is of the sand is decreasing the relative density is increasing and then the SPT value is also increasing it just gives you a feeling how does it change from very loose to very dense material then if we know the SPT value you also have the angle of internal friction as a function of the SPT value this gives you that function so you can also see here loose up to very dense so in fact that's the relative density again and so if I would have 40 SPT which we consider a hard sand okay 40 that would mean I'm here I would have an angle of internal friction of 38 39 degrees this method is not very accurate in fact the red lines give the upper and lower limit which is plus and minus 3 degrees but if you don't know anything you have a method to determine some values of the sand well if this way I estimate my angle of internal friction and I take two-thirds of that value I have my angle of external friction so I can make some estimates well last thing before the break then we get to specific energy what is specific energy specific energy and it counts for all types of soil not just for sand all types of soil if you divide the cutting power by the production q is the volume flow of material so that's the production cubic meters per second if I divide those two I get energy per cubic meter well the power is force times velocity that's general for power the production is the layer thickness times the width of the blade times the cutting velocity and then you can see the cutting velocity is in both so apparently I can divide the VC out of the equation if I do that for the cavitating cutting process and I do that because in dredging with cutter heads normally the velocities are so high that it's always cavitating so that's what we are interested in you get this simple equation for the specific energy I already told you the d if you don't know anything take a value of 5 okay so if I take a 5 rho times g is 10 and suppose the water depth is also 10 you get 5 times 10 times 20 is 1000 kpa which means my specific energy for such ascent would be 1000 kpa here you see the equation again now you can also reverse this and say okay so if I know the installed power of my cutter head I just reverse the equation and I can determine the production so the production is the installed power divided by the specific energy so suppose I have a cutter head with 1 megawatt installed power 1 megawatt is 1000 kilowatt if I divide 1000 kilowatt by 1000 kpa I get 1 dat would mean such a cutter head has a production of 1 cubic meter per second this is based on just energy considerations so I'm not looking at the cutter dredge and check if the cutter dredge is capable of having such a swing speed that it can do 1 cubic meter per second I didn't look at that all I look at is the power of the cutter head enough to cut 1 cubic meter per second well in this case in this specific example it is because specific energy is 1000 installed power is 1000 if you divide it you get 1 cubic meter per second well this is the way to determine your production there are other limitations which I will discuss later but at the exam you could get questions if I have such and such a sand determine the specific energy I have a cutter head with so much installed power what would be the production but I can also reverse it and say if this is the production what should be the installed power or whatever you can do it in many directions based on the previous slides where I had a relation between the SPT value en de angle of internal friction I derived those equations those 3 equations for 30, 45 en 60 degree blades where if you know the phi the angle of internal friction you can determine the d1 and if you do that for something like 35, 40 degrees for the 60 degree blade you should get close to the 5 but in fact the d1 could range from let's say 2 to 10 that's roughly the range ok we have a break well we saw the specific energy so here you see the equations again and here I made a graph with horizontally the SPT value vertically the specific energy of the sand and a set of water depth so we start at 0 meter water depth and we end at 30 with steps of 5 meter and you can see where you are well normally hard sand would be in the range of 40 to 50 SPT and if you look at that 40 to 50 SPT you move up well the first line would be 0 meter water depth and you would arrive at something like 600 kPa specific energy but in the example I gave before the break we said if we have 10 meters we would arrive at about 1000 well look at the 10 meters which is the straight line here 40 to 50 straight line we are close to the 1000 kPa so that works but if the water depth is bigger for every 10 meters of water depth you can multiply the specific energy with a factor so 0 is 1 10 meters is 2 20 meters is 3 et cetera et cetera so every time you have to add up the number 1 so if 0 meters water depth would be 500 kPa then 10 meters is 1000 20 meters is 1500 30 meters is 2000 and that means if I go from 10 meters to 30 meters the specific energy doubles and that means the production goes to 50% so with the same cutter dredge the amount of sand I can dredge but this is the maximum it doesn't always mean I'm dredging the maximum but if I would dredge the maximum then at 30 meters the maximum is 50% of the 10 meters this chart gives you the productions per 100 kW installed power on the cutter head and you can see how it is decreasing with increasing SPT value but here both axes are logarithmic by the way yesterday I already put all those slides on blackboards so you can check it and I'm almost ready with the lecture notes so I will also put them but I still have to write some text the lecture note you will get is not yet 100% finished because it's too much if I would finish it in one year I would work full time on just writing lecture notes but there is enough for all the lectures to understand and to see all the equations that you need experiments well, we used to have a laboratory and I just saw Mr. Nief from China his father is the dredging professor in Changzhou in China and he just told me they are building a new laboratory, some of the biggest dredging laboratory in the world, somewhere in China but at the location of his father in Changzhou, close to Shanghai they also have a laboratory like this we used to have one but because of Delft University policy another group needed that space so we lost that laboratory we still have a laboratory but not as big anymore we used to have a laboratory with a big concrete tank that tank was 2,5 meters in width about 36 meters long and on top of the tank there was a carriage, a vehicle that could drive over the tank and under that vehicle you could mount blades or cutter heads or whatever you want it was driven by a winch an infinite winch and we had a cabin with all the measurement equipment to get all the data from all the measurements this is a cross section of that tank so here you see the concrete tank here you see a side tank why did we have a side tank because if you do cutting tests you get a lot of turbidity of the sand moving up and that would mean with an underwater camera you cannot see anything because of all the turbidity so for example when we do tests with a cutter head the sand goes into the suction mount which is this pipe is transported through a pump dumped in the side tank and that way we could keep the water clean at the bottom, this is the sand we had a drainage system so we could pump in or out water why did we do that well if you pump water in and in fact we needed the fire department connections to have enough flow we could make all the sand fluid and then if you do that so you pump water up all the garbage that is in the water will float to the top like clay particles or real garbage and you could scrape it away one time and that way keep the sand clean because if you get too many clay particles and fines in the sand it influences the permeability and you don't want that you want to have a very controllable permeability so that's when we pump water in when we pump water out we create a huge under pressure at the bottom of the tank en dat way you can compact the sand much better later I will show you how we really compact the sand well this was the carriage so you see the big tank and the side tank here we have a so called dustpan so after a test we can suck out the sand and pump it back to the main tank this is a cutter hat that we used 40 centimeter in diameter this one was for cutting rock and here this is that same cutter hat this is a cutter hat with smooth blades and we use this one for cutting clay I already told you if you have clay with a high adhesion it will stick between anything it can stick so if I would cut clay with this cutter hat within 5 minutes it's completely filled with clay and blocked and I can't dredge anymore but if I would use this one it's okay here you see the carriage with a blade at the bottom in fact I just did this in coral drawer because the real blade had too much rust on it so I just painted it this is the real blade and you see the sand here this is how we mounted the blade under the carriage so what you can see is a center blade and two side blades and each blade is mounted in force transducers and moment transducers torque transducers and why is it well the theory is two dimensional so if you want to check your theory you need to have 2D tests so on the center blade we measured the 2D process and on the side blades you also have the side effects which are 3D so we could distinguish between the center blade and the side blade for later research we put a window here with a camera behind it so we could actually see we were moving over the blade now when you do a cutting test the distance between those blades has to be very small because you don't want sand to go in between but on the other hand they shouldn't touch each other because you get a force influence if they actually touch each other but what happened at some tests when building the laboratory some people were welding in the neighborhood of the tank and after finishing the welding they just throw those small pieces of welding material into the sand and when we did tests so that's like I would say 3mm, 4mm thick bars from the welding device actually they went through this gap the gap was only 0.1mm but the forces were so high that the pressure pressed them in between and behind the blade we had those pressure transducers with pipes and so on and those welding things they went straight through it and everything was broken so the forces and the stresses can become so high that something you don't expect will still happen this is the whole mounting system I just show it for your information so the center blade and the two side blades here you see what we call dynamometers to measure forces and torques so we could actually measure everything those are the blades so you can see how they were constructed this is the actual blade but this is the holder and it has this shape because you don't want the holder to influence the cutting process it shouldn't touch the sand here you can see a blade with a wear flat so we welded a triangle of steel at the tip of the blade to simulate wear of the blade and we also did tests with that this is 45 degrees, 60 degrees, 30 degrees and we also had a 15 degree blade but then you can already imagine it's too flat it becomes too flat the tank had windows and we actually mounted cameras on the outside connected to the vehicle so if the whole thing is moving the camera is also moving and then in front of the blade you can record what is going on but only if the water is clean but we also used underwater cameras in fact we mounted a camera in the back of the blade so because the first thing you do when you do research you want to observe the physics don't just start with equations or whatever first observe the physics do some orientation tests see what is actually going on so you get a feeling this is what is happening and describe it in words not in equations, describe it in words because if you are not capable of describing in words what is going on you can never explain to other people what you are doing so the first step is just in words explain the physics in words here you see that window again and this is when we prepare the sand because you can tell there are sand in the tank we just do a test but you want the tests to be reproducible every time the sand should be the same so this is an eagleizer here to make the sand flat have a flat bed and here you see two concrete vibration needles en we use those to compact the sand because you don't want blue sand blue sand doesn't give a problem we like very dense sand how to make the sand dense well, the car, the vehicle will move with very low speed over the sand those vibration needles vibrate the sand that way they compact it and at the same time we found that if we put the drainage system on and suck out the water creating under pressure in the sand we get a better reproducibility of the sand so then each time the sand is almost the same 100% is not possible but almost what did we get out of such a test this is just a sheet as an example, the raw data we have six signals horizontal force, vertical force and then four pore pressure transducers where P1 is at the end of the blade and P4 is at the tip of the blade and you can see that both the forces and the pressures are not nice constant signals in time but they go up and down we had already told you that the failing process of sand is the shear type where you have a build up of pressure when the pressure is high enough a shear plane shoots to the surface that releases the pressure on the blade it moves forward, builds up the pressure again you get a shear plane again etc so this up and down, what you can see here every peak is a shear plane shooting to the surface and based on that if you count the number of peaks in such a signal you know the number of shear planes that you had and you divide it by the time and you can find the distance, the thickness of each shear plane so that's the reason why it's not a nice constant force but it goes up and down what is that? oh, ja, now it works ok, this is a picture of measurements of those poor pressure transducers in fact over a whole test we determined the average of all those signals and the average we put in graphs well what you see here, this is the blade and you see the location of the pressure transducers this is two series with a wear flat and without a wear flat the blue line is the result of the finite element programming so the numerical solution you can see the red with the wear is a little bit above the theory the green is a little bit below the theory but in general it matches pretty well and if I would change the size of the wear flat in the finite element calculations I could reduce or increase this peak that you have near the edge that one was for a very long blade you can imagine, well if I show it again if you have a very long blade most of the under pressures will occur near the tip of the blade but then it reduces rapidly but if I have a very small blade and small is in relation with the layer thickness then I get a shape like this and again you see the measurements with wear and without wear so with wear is always a little bit higher because the water cannot flow there so the under pressures will be a bit higher but the difference is not so much that I really need two separate finite element calculations for it here I have measurements the previous two graphs were dimensionless so I divided by many things to make it dimensionless here you have measurements in absolute pressures but in meters water column not in Pascal, but meters water column well the maximum you have is 10 meters water column because the amount of water above the center is so little we can neglect it that means if I get an under pressure of 10 meters water column I have full cavitation well what we got you can see what happens this is the cutting velocity and you can see the lowest one the blue line here well I'm far from having cavitation but if I go to the highest speeds up here then near the edge of the blade I have 9 meters under pressure or something which is already close to cavitation one thing you have to keep in mind when you do such experiments and that's again air if you would just have like less than 1% air in the water and air is compressible also expandable then I made calculations for that that with just a little bit air in the water I would never reach the 10 meter water column under pressure I would be stuck at about 9 meters just because of less than 1% air in the water and if you see how the water is pumped into such a tank with a lot of turbidity you can imagine er altijd be some air dissolved in the water and in fact if you have very tiny air bubbles in the sand it's almost impossible to get it out because you cannot put the whole tank in a vacuum tank it's too big so once you have some air in the sand it will be there and then with thermodynamics you can calculate how the air will expand if you get those under pressure so that's the reason why here we don't actually reach the 10 meters it's just because there was some air in the water this is the same but for a sand with a lower permeability because the lower the permeability the higher the under pressures and here you can see for small velocities we don't have cavitation but for the highest velocities you can see that shape that I showed you theoretically so everywhere you have that cavitation area close to the blade you will have an under pressure which is close to the cavitation under pressure then some forces horizontal forces this is from three sets of measurements and the blue line is the theoretical line and you can see that the measured points are a little bit higher than the theory but not that much if in reality you can make an estimate within 10% every company will be happy so the difference that you see here is not much and in fact you could say why not adapt the theory so it matches exactly you could do that in a set of tests and then it's below and then you have to adapt it again so the theory with the constants that I have in the theory are already based on many experiments and in fact I always feel theory doesn't have to match 100% with experiments as long as you get close enough this is the vertical force if you look at the horizontal force you can see a scale to 5 if you look at the vertical force you see a scale up to 1.5 and that's because the vertical forces are always much smaller than the horizontal forces a positive force means it pulls the blade into the soil a negative force means it's pushing it out and in this case everything is positive here you can see some tests in a sand at different layer thicknesses with speeds up to almost 1.5 meter per second and red is 25 millimeters green 50 millimeters and blue is 100 millimeters and especially with the blue line well here you can see it better it follows the curve this part is no cavitation and the horizontal part here is with cavitation so the fact that in the beginning it's increasing almost proportional to the velocity but above a certain point it's almost independent of the velocity you can see here so it matches pretty well horizontal force this is the specific energy and you can see that the specific energy in this case is bigger for a thinner layer snowplow effect we already talked about the snowplow effect that in general blades are not perpendicular to the cutting velocity but they are under an angle if you have a 3D curved cutter head and you divide the cutter head in small parts such a segment will never be perpendicular to the absolute velocity so it has a certain deviation angle with the velocity well here we have tests with zero degrees deviation so the blade is perpendicular to the velocity horizontal force, vertical force and specific energy and this would be the side force because of the snowplow effect but it's zero if it's perpendicular but in this case you have a 45 degree blade so it deviated 45 degrees so it's a snowplow under 45 degrees and suddenly you can see that you also get a large side force and the curves is what we calculated and the points is what we measured so we actually did this kind of research and you see that it gets close enough horizontal force and side force get close enough for the vertical force you could say there is some deviation but then on the other hand the forces, the vertical forces in general are so small compared to the other one here you have ten well most of the forces are like 1.5 and in the negative direction almost nothing that means if I have a force where the vertical force is almost zero then the factor is horizontal if something happens and this factor is moving a little bit downwards it has a very large influence on the vertical component but hardly anything on the horizontal component and that's what's happening here so the two horizontal forces this one is straight forward and this one is to the side they have quite a magnitude the vertical force is always small compared to those two we also like to determine the friction based on tests you can do it in a laboratory but you can also from your cutting test you can also try to derive it in fact what do you measure a horizontal force and a vertical force then if you use poor pressure measurements or finite element calculations you can determine a normal force a friction force and the two poor pressure forces oh it looks like the battery is empty so factorial you can make such a graph and that way determine what would be the delta value that we actually had during the test so we also did that and that's how we found that using two-thirds of the internal friction angle is a good way ja heb jij nog een nee verkeerde batterij gebruiken we die gewoon ok, so that was the normal cutting process and in some cases I already explained in the beginning in the cutting equations we divide by the sign of the sum of four angles and if the sum of those four angles gets close to 180 degrees it means you will divide by almost zero and then the cutting forces would become infinite well, nature will not do that so nature will find another way to deal with that problem so nature will create a wedge and this wedge can be static and it can be dynamic if we call it static it means the sand inside the wedge is not moving anymore it doesn't have velocity if it's dynamic it means it's still moving but maybe not with a constant speed or anything maybe you have a velocity gradient somewhere but it could still move so if we say ok, this is what's going to happen if the sum of those four angles gets too close to 180 degrees then how to determine the shape of that wedge because you can see the wedge has an angle theta, we call it the wedge angle if I know this wedge angle I could calculate everything because I can put it in a finite element program to determine my under pressures I can solve the equilibrium of forces moments, all those things but I have to know this theta well, first of all and you already saw those pictures but not for sand first of all we have to look at all the forces that we have and in this picture I only put the forces that we have in sand in the picture you saw last week I think I also, I really put all the forces so also adhesion, cohesion and so on here you only see the forces that you have in saturated sand so what do we have on the shear plane normal force and shear force and the pore pressure force and on the blade also normal force, shear force and pore pressure force all the other forces we are going to neglect they are either not there of they are so small that they do not influence the process then on the wedge it looks more complicated but in fact it's not really you have the same set of forces on each plane a normal force, shear force and pore pressure force and the thing is how to get them how to determine them but in this case having two equations for vertical and horizontal equilibrium is not enough we also need the equilibrium of moments and this is the forces on the blade you already saw such pictures before and here you have the forces that determine the moments so you have the normal forces and the pore pressure forces you have to know both in order to determine the equilibrium of moments we take the equilibrium of moments around the edge, the tip of the blade but you could do it in any point if there is an equilibrium of moments it should exist around each point the thing is, if I use the tip of the edge many forces go through the tip of the edge so I do not have to take them into account for the equilibrium of moments like the shear force on this plane goes through the tip of the blade so it doesn't result in a moment and then the equations become more simple so the choice of where around which point do you take the moments just depends on what makes the equations as simple as possible we have the same problem with the pore pressure the water flows to the shear plane but actually so this plane is sheering you have dilatation here here you do not have dilatation since the sand can only have dilatation once and if it is a static wedge in front of the blade that sand can only have dilatation once it expands it will not expand more so in the wedge in the wedge and on this plane I do not have dilatation only in the shear plane same picture as before for determining where does the flow come from with the boundary conditions of the finite element program again a coarse mesh although this one already looks pretty fine and here you have a fine mesh and this is the result and what you see from those calculations you get the highest under pressures in the shear plane but in the wedge not much is happening what I found is for the pore pressure calculations you can almost say I just assume the wedge is also made of steel and then the results of pore pressure calculations do not really differ much from what we did with the finite element program so in our calculations the water could flow through the wedge although we didn't have dilatation there but the water could flow through but it didn't really influence the pore pressures in the shear plane a lot so you could almost use the same values well here you see the flow lines and you can see the yellow which is high flow but in the wedge you can see there is not much flow based on the colors and this graph shows how the pore pressures develop along the different lines so from A to B or B to AB is where the shear plane reaches the surface so there your pressures are zero because you have hydrostatic pressure then you see the curve going to A A is the tip of the wedge not of the blade but of the wedge then from A to D you have the bottom of the wedge so you go from the tip of the edge to the bottom to the tip of the blade you can see how that develops then DC is the blade itself and CA is the top of the blade to the tip of the wedge in that direction and you can see how it develops the top one is for a case where you have a blade and such a wedge with a shape like this so a 90 degree blade with quite a wedge this one is the case where you have like such a blade and then a small wedge in front of it and that's why the bottom of the wedge is very small and this distance is the bottom of the wedge and then you can see what that looks like en in fact such a calculation should almost give exactly the same result as the case where you don't have any wedge so that's a way to check if the calculations are correct one more slide I think no we will stop here and then tomorrow continue with a good laser pointer


Tony has had two careers, the first one with Roy Schertz, where he worked in a number of different countries and secondly he worked from 1990 to 97 at the independent in London where he was successively East Europe editor and Europe editor and I suppose most of us know him for his career with the financial times which he has been in since 1997. Today, according to my brief here, he's going to argue that Theresa May's government will no longer be able to avoid necessary choices between hard and soft Brexit and that these decisions may expose the internal contradictions of the political and electoral coalition that rejected EU membership in June 2016. He will analyse the possible impact this will have on British politics in 2017. It's a fascinating perspective and we look forward to hearing it. Thank you very much Tom, ladies and gentlemen. The people of Britain and the EU 27 should I suppose be grateful to Theresa May for setting out her Brexit vision last Tuesday. Without the Prime Minister's guidance, we might have spent this event in much fruitless speculation about the objectives of the Conservative government in taking Britain out of the EU, forging a new relationship with the 27 and redefining Britain's place in the global economy. That said, May's speech by no means answered all questions and the reactions of some Brexiters raised questions of their own. The leader of the right wing populist anti-immigrant UKIP party graded her speech 7 out of 10. That reminded me of what Dora Gateskill said to her husband, the late Labour party leader Hugh Gateskill, when he gave a speech at the Brighton Party Conference of 1962, declaring that a federal year would mean the end of 1,000 years of English history. Amid the stormy applause, Mrs Gateskill murmured to her husband, darling, all the wrong people are cheering. Today I propose to devote some attention to the uncertainties that hang over the process of British withdrawal and the nature of the future EU-British relationship. I won't linger on the possible reasons why in a gloss on May's speech Boris Johnson, the foreign secretary and master of the gratuitous insult, compared the French president with a second World War camp guard administering punishments to prisoners. Instead I want to focus my remarks more on what seemed to me to be profound contradictions in the government's longer term strategy for post Brexit Britain. Contradictions which have their origins in the political and electoral coalition that won last June's referendum and which are likely to become increasingly visible and awkward for the Conservative Party as events unfold this year and next. Let's remind ourselves of the key points in May's speech. Britain is to give up membership of the EU single market, but in some sectors such as financial services and vehicles will seek privileged access to it. Britain will also pull out of the EU customs union in the sense of not sharing the common external tariff or the common commercial policy, but it will seek some sort of customs agreement with the EU to keep cross-border trade as frictionless as possible. Britain will go down this road, she said, because it wants to recover the right to control migration. It wants to escape from the jurisdiction of the European Court of Justice and it wants the freedom to strike trade deals wherever it chooses. However, Britain wants a comprehensive free trade accord with the EU. Britain intends to maintain a close relationship with the EU in matters of defence, intelligence cooperation, counter-terrorism and crime fighting in general. Britain also forces close ties in areas such as science, research and education. In fact, Britain is willing to make an appropriate, though not vast, contribution to the EU budget to secure such ends. Above all, she painted a picture of a global Britain shaking off the shackles of a Europe too small and stifling for British ambitions. Yet, Britain wishes the EU well and wants it to succeed, she said. However, and here I'm reminded as a former Moscow correspondent of what Andrew Gromyko once told the Soviet Central Committee about Mikhail Gorbachev, comrades, he has a nice smile but teeth of iron. She added that if anyone in the EU was thinking of punishing Britain for Brexit, it would be, and I quote, an act of calamitous self-harm for the countries of Europe and not the act of a friend. Should this happen, the government might even change the basis of Britain's economic model by which most commentators have understood an attempt to undercut mainland Europe by such means as slashing corporate taxes and offering unmatchable incentives for foreign investment. Some brief remarks on that last threat. Britain's tax base is already stretched close to the limit. The health service, social care, pensions and other areas funded by public expenditure need more money, not less, to appease a restive citizenry. May had nothing to say about how bargain basement corporate taxes would generate the revenue to address these urgences. Be that as it may, to what extent are the May government's goals achievable. The timetable for the withdrawal on negotiations is very tight, not least because of the European electoral calendar this year, the sheer complexity of the issues at stake and the need to allow time for ratification of a deal between late 2018 and March 2019. It is not hard to imagine an acrimonious atmosphere emerging at the talks early on because of all sorts of disputes, starting with Britain's so-called bill for leaving, which at least one EU policymaker estimated at 55 billion to 60 billion euros. Naturally, the only Brits who appreciate that the EU may have a case on this point are quote, citizens of nowhere, as may provocatively label them in her speech at last October's Conservative Party conference. Another complication is whether discussions of the future EU-British relationship will at some point run alongside the Brexit negotiations. For what it's worth, my own view is that it will be difficult in practice to separate the two at some point. Yet the idea aired in May's speech that it should be possible within two years to lay down the framework of an EU-British free trade deal, including access to the single market for specified British business sectors, strikes me as ambitious to put it mildly. I'm not saying that eventually something along these lines won't be the outcome, but on the EU side, the multiple divergent interests of governments, parliaments, business lobbies, unions and constituencies of all kinds will need to be reconciled. It will be an arduous process, scarcely smoothed by the possibility that the European political landscape will look substantially different in late 2018 from how it looks today. What can be predicted with some confidence is that the EU will not tamely grant Britain privileged market access for sectors such as car manufacturers. As Donald Tusk put it last week, there will be no place for pick and choose tactics in our negotiations. Both politically and technically, selective single market access may in certain areas just not be possible. Let's consider the letter which the British government wrote to Nissan last year promising that Brexit would not harm the company's interests as a British based car maker and exporter. We don't know the letter's precise content, but its message was that the government would ensure that Nissan could continue to operate within the single market, the customs union or equivalent rules. After May's speech, this letter looks like a hostage to fortune. To the extent that she prioritises the car sector or others such as aerospace or pharmaceuticals, the EU's negotiators will at a minimum push for British concessions on other fronts. To the extent that she yields on the car sector, for example, to protect the city of London's interests, she will risk affronting Nissan and the Japanese government, which after the June referendum spoke with unusual firmness about why it wanted to Britain to retain broad, trouble free access to the European market. Her vision of partly privileged market access will generate some pushback from British industry too. According to industry and trade people I have spoken to, you cannot simply ring fence the auto sector from other manufacturing sectors and include the former in the EU market and customs union, but not the latter. Supply chains and the overlap between different sectors are too complex to permit that. As a result, it is easy to imagine that pressure would build up from other British manufacturers and exporters to the EU to be inside any special arrangements set up for the car sector. The larger point here is that many British businesses fear being supplanted by European competitors in global supply chains because the Chinese, US and other manufacturers who form part of these chains will see it as a priority to stay inside the EU customs union and its VAT regime. What about May's plan for a quote global Britain? It sounds attractive and even sincere if you can say that of a political slogan, but it conceals what I referred to at the start as profound contradictions in the pro-Brexit political and electoral coalition. Global Britain, as I said, proceeds from two assumptions that EU membership has restricted Britain's worldwide opportunities and that the EU is, economically speaking, if not all washed up, then certainly ragged and damp. In a report that came out last week from the Eurosceptical Bruges group, which has long exercised influence over anti-EU elements in the Conservative Party, the author stated that Britain, quote, should not be hemmed into little declining Europe. To this one can respond that anyone who considers German business to be little in declining must be living on Mars. Then again, is it really true that EU membership has confined any member state, including Britain, to some mouldering, walled-off European crypt of the world economy? May admitted to mention that Britain actually sells less than comparably sized EU economies to China to take just one big non-European market. If Britain, if France and Germany can outsell Britain in China, then EU membership is a flimsy explanation for Britain's less prominent place in Chinese trade. Forgive my carping, I fully recognise that for some Brexiters the notion of economic self-liberation from Europe was and is a captivating vision. This vision encompasses bonfires of business regulation, zero tariffs, the removal of non-tariff barriers, nimble and competitive new age industries springing up in Britain, lean and hungry exporters piling into non-European markets, everyone's safe in the knowledge that for the British government protection is a dirty word and red tape is for fools, lawyers and wimps. But is this what all leave voters had in mind when they backed Brexit in June? I think not, as the Prime Minister noted. The vote was in some degree a vote for migration controls. But you cannot build global Britain without a labour market open to the best, the brightest and sometimes the less well-paid recruits wherever they may come from. On this point, all sorts of British businesses from engineering companies to the creative industries are adamant. Moreover, the linkage between global Britain and an array of rapidly negotiated prosperity boosting international trade deals starts to look more complicated than may made it sound when you consider the case of India. India will not give her the trade deal she wants without reciprocity in the form of a liberal British migration and visa regime for Indian skilled workers and students. In short, the political imperative of imposing migration controls dictated by one half of the pro-Brexit coalition will clash with the economic imperative of establishing less restrictive migration rules needed to fulfil the goals of the Brexit coalition's other half. The leave vote was also inspired in part by insecurity, not joblessness but stagnant or falling living standards, poorly paid work, a shrinking welfare state and the feeling that the gap is widening every year between the advances of technology and the receding possibilities of social and economic self-improvement. Yet, unlike in 1979, when Margaret Thatcher was swept to power thanks to a widespread sense that Britain's economic malaise needed drastic treatment, the angry voters of June 2016 were not calling for a radical pro-business revolution. They do not want Britain to be Singapore on the channel. They want simpler things, better wages, affordable housing, no more hollowing out of the health service. To an extent may took account of this in her global Britain speech by saying she would not only uphold workers' rights as set out in EU legislation but enhance them. We shall have to see what her words amount to in practice, if anything, but we already see the outlines of disagreement between her wing of the Conservative Party fishing for votes among disaffected labour and recently converted UKIP voters and the other wing which dreams of a Thatcher type dash for free market glory. Perhaps the two wings can be reconciled if the British economy performs strongly over the next two years and more. The early signs are not promising. This year the economic headlines will be dominated by rising inflation, wages that fail to keep pace and a glaring failure on the part of British companies to exploit Stirling's plunge since June by boosting exports. This in turn will pile pressure on the already high current account deficit and the budget deficit, making tax increases more likely, not less, and exposing the economy's so-called resilience over the past seven months as built on sand. To give you an idea of what is in the pipeline, it was reported on the very day of May's speech that consumer price inflation went up to 1.6% year on year in December and input prices for companies soared by no less than 15.8%. In these figures lies a profound truth about the British economy which explains why Brexit will be hard going and why a switch to a different economic model is pure fantasy. During its 40 years in the EU and as a result of globalisation Britain has become deeply integrated into European and world supply chains and its domestic manufacturing base has shrunk decade by decade. More and more companies source their supplies from abroad, not from domestic businesses. With a depreciating currency this heavy reliance on imports stokes inflation. One way to change this would be to rebuild Britain's manufacturing base. The Prime Minister is saying some things about this today I believe in Britain. But the fact of the matter is that the skilled domestic workforce, engineers, computer technicians and so on doesn't exist in sufficient quantities. That points to keeping the door open to European and non-European employees but as we know such a policy would contradict the pledge to cut back immigration. As the year progresses, frictions will develop in the Conservative Party as the realisation dawns that the economic strategies available to a Britain outside the EU's single market are also the strategies most at odds with the political promise of Brexit. Brexit, it's a big topic and I apologise for not covering it's every angle. Let me conclude with some observations on the UK's internal constitutional settlement and the all important relationship with Ireland. In her speech May was almost brutal in ruling out special Brexit arrangements for Scotland. This does not necessarily accelerate the timetable for a second Scottish referendum on independence. Right now the economic and fiscal outlook in Scotland is not at all favourable for holding another referendum. Moreover at the moment there is no automatic correlation between Scots who voted to stay in the EU a 62% majority and Scots who today support independence well short of 50%. Yet the inescapable fact that the Brexit vote, the Brexit negotiating process and post Brexit British economic policies were and will be dictated largely by the English and English Conservatives at that means that the constitutional issue will remain very much alive. To bury it would require in my view some far reaching political realignment in Scotland including the revival of Labour or some similar pro unionist party of the left and that seems at present to be a very remote prospect. As for UK-Irish relations clearly the priority must be to preserve the common travel area between the North and the Republic to avoid customs trade and investment barriers and most crucial of all to uphold the peace process and promote harmonious community relations in Northern Ireland. I trust that didn't sound like a pious wish list and I hope you won't label me short-sighted or polyannerish if I say that May and her ministers have so far spoken on Irish matters with a caution even the maturity that are often shockingly absent from their remarks on the EU. Just think of Boris Johnson. I expect this sense of responsibility to prevail no matter how fraught the Brexit negotiations become. That said constitutional instability in the UK cannot fail to have profound implications for the Republic. As I indicated it would be naive to assume all will be calm on that front in coming years. Ladies and gentlemen against the sweep of 20th and early 21st century history Brexit looks less like an abrupt about turn for Britain than the culmination of a trend of increasing detachment and disenchantment that was set in motion almost from the very moment the country joined the old EEC in Ireland's company in 1973. Still Britain is undoubtedly setting out now on a new uncharted course and it will just have to make the best of it. Or as Samuel Beckett put it, ever tried, ever failed, no matter, try again, fail again, fail better. Thank you.


Hello everybody and welcome to another hobby cheating video and today we're gonna do something fun we're gonna paint most of a figure and We're gonna do that with the new lady of vines which games workshop was nice enough to send me early So thank you very much. I really really love this figure I think it's really gorgeous and I wanted to use this as a chance to talk about resolving things like wood and Flowers and surfaces like this That might be a little samey like most of her is sort of the same material, but we're gonna make them interesting Not probably what the video title is gonna be Let's get into it. Let's strict techno man sir that is fancy V Let us get to the technique and learn it in CV style as I mentioned The lady of vines is a really compelling figure, but the challenge with figures like this She's mostly made of wood now They gave her some shoulder pads and maybe a couple other little elements that are meant to I guess be different be meant to be metal Which is kind of strange that this tree person has bunch of metal built into them But I'm not asking questions ever and you probably shouldn't either and so today We're gonna walk through and I'm gonna basically share with you my tips and tricks for how we make figures like this a little more Visually interesting while still painting them fast and efficiently. This should be really fun Let's turn our lady of vines into a lady of cherry blossoms Let's do this The paints are gonna roll up at the top and we're gonna cover basically all of this model So I'm really gonna be talking about more what I'm thinking and why I'm doing what I'm doing My initial instinct here is just to get some base brown color down. She has made of wood seems reasonable enough Wildwoods quite dark. So it gives me a nice dark base to work from I'm not using straight wildwood Nor am I pre thinning it instead I go into the bottle apply it and then I go into a bunch of contrast medium and Smooth it out. I find this works a lot better and gives you more even sort of coverage across the model Walls still collecting it in the recesses The journey here over the rest of the highlighting on the wood is gonna be all about bringing out and creating texture So wood is naturally quite rough When we often paint, I think smoothness becomes sort of this Thing we're trying to achieve as though it's some magical property that will make the paint job exceptional One of the reasons I love painting Sylvaneth is because they free you from the shackles of such non-sensory And instead most of the time when I'm painting you're gonna see I'm painting in thin staccato lines and dots and things like that intentionally not trying to properly blend it or something like that But my goal here is to create texture namely wood texture Now I am focusing in this texture on the areas where the highlights would normally be on the model. So her Right knee here is extremely far forward. It's a natural place where a highlight would fall So we're going to as we build up through these browns and whites and such We're going to really focus the texture in those areas And I actually have two purposes here one to reflect the light but two also to show sort of the I don't know new growth of wood. It seemed more visually interesting if the edges of her armor were sort of constantly regenerating and growing Kind of like a mouse's teeth, I guess and so as I build this up I'm not worried too much if I create too much contrast or too much texture You can knock it back quite easily later And so the advantage to this is you can really just go nuts and have fun I think Sylvaneth is truly one of the most fun armies to paint because of the freedom to use lots of different colors lots of different textures and In the end be able to integrate all sorts of things like contrast and washes and just have a good time So as I push higher and higher here, you'll notice I don't always cover the exact same space But I'm always trying to bring out that texture again continuing these little staccato lines and dots Now I take this quite bright in the highlight areas But you'll notice that it's only those most highlighted spaces that get these final touches So the center of the face that I want to draw attention to maybe the base the neck the very top of her chest The very stuck-out knee the top knuckles The edges of the branches above her shoulders that are sprouting these grappy grappy vines I want to make sure that those areas have a lot of differentiation But I still want to also be able to bring them back in and this contrast paint that I'm using here It's really all about creating more additional color and tonal variation By taking this thinly using it more like a filter Over some of the lines. I already have you get a different effect than if I just tried to build up through the brown The brown skeleton horde Contrast is going to act like a great filter that sort of integrates all these different Lines and color variations that I layered together into a more harmonious single Figure while also creating more visual interest It also lets me hide some of the maybe shoddier lines or things like that where my brush wasn't quite in as much control as I would like While also then creating new and great tones. So it's good all around Notice that a lot of what I'm doing here is trying to resolve and create lots of changes between light and dark Now that's a sort of understated thing I could probably do a whole video on it And maybe I will in the future But one of the great tricks to painting miniatures is to just alternate between very light and very dark repeatedly and close together Look at paint jobs. You really enjoy and really look at them. Don't just look at them Maybe see them you'll notice that they tend to alternate light and dark quite often in very bright sharp changes That's often what makes a model look clean compelling and keeps your eye moving around it So that's why we're doing it here, especially with things like the wood to integrate these elements in So being relatively happy with the wood now It's time to move on to the other colors and we're gonna begin here with the vines Now I wanted something that was a bit unusual So I chose this oxide green light in the end. I'm not sure if it was the right choice. You could use any green I think maybe I should have gone with a more deep foresty green But it seemed an interesting choice and I wanted to play with it Some part of painting models has to be fun and experimentation and trying things even if it doesn't work out perfect We still always learn and that's valuable in and of itself But I like to the tone of this. There's a little bit of yellow in it and it seemed interesting I also took a little bit of this as a glaze and worked it around what I saw as those fresh growing wood tree especially like new Bark or something or new fresh heartwood when it's growing will often have a slight tinge of green to it I think of it in my head like a banana though. I know that's not great and not correct But I wanted to work a little bit of that in Maybe show a little bit of moss a little bit of life a little bit of growth and again always pushing more color into areas That are otherwise completely in neutral tones Now I had to bring together the green with the wildwood so a simple mix and a glaze over the top Smoothes those two out. One of the nice parts is that those two paints just work really well together Brown and green just go really well and so that you can hide the sins of that layer line really easily Deciding to re-instantiate some of the deeper tones and recesses. I'm effectively made a wash out of the Green-black ink and I'm just running that over all of these vines It also you'll see I take it all the way up to the sort of root where the vine is sprouting to once again hide that transition line But by working this ink in here. That's very dark, you know, green black is a pretty dark ink I just mixed this ink by the way with a little bit of water and a little bit of flow improver bang bang Bob Jerome Well now we've got a wash And I was able to sort of get those deeper shadows back in place But the other way I could build contrast was by taking the edges of the vines up So with increasing amounts of buff into the oxide green I start picking out the individual vines Focusing especially on the edge, but not only the edges. I do crawl back up to the areas of the vines that would also be Sort of at the top or extremely lit by light wanting to make sure that's really captured As a side note, this was an almost impossible miniature to film painting So I apologize if some things happen to be on the edge of the screen or slightly out of focus This girl is truly wild with how much she's spreading every you know out all over the place and Proved an interesting and constant challenge to actually film what I was doing so great pick to film painting a whole model I knew I wanted to do something with the chest to break it up. She has this sort of ornate Pattern around there that's clearly some kind of different material So I decided to take it into the same green vines. It makes sense if she's the lady of vines She probably has this sort of vine iconography on her chest quote-unquote armor Just like anybody else would have you know a key aquilas or whatever else they have on their chest And then I just needed to put in that nice black line to get that separated and really make sure that the green Stood out from the lighter woody colors that were around it and in the end I like how that worked It actually felt sort of like a naturalized Take on what would be a standard warrior's metal armor. So I thought that came out pretty well Hugh Hugh variation I talk a lot on this channel about tonal variation and here it's important as well When we're dealing with neutrals like wood Right, so a lot of this figure ends up being some color of brown or maybe even you want to go dark wood Maybe it's like black or something like that, but it's wood. So it's going to be a neutral tone Browns are by their default As an acrylic paint somewhat uninteresting to the eye as I've said in the exploring colors brown video Only 3% of people list brown as their favorite color However, Hugh Those things on the color wheel so not white not black not browns not tans anything like that The colors that exist around the color wheel tend to be much more compelling to human eyes So we're really going to look for opportunities to work those colors in in a compelling way and in this case We're going to use the soft soft Complementary colors of this off green and pink to create something that's visually compelling or at least I hope so You'll be the judge of that in the end. I suppose. Let's get back to painting Our tones thus far have been fairly desaturated or or neutral all the woods even the green is a fairly desaturated green It's not really a wake up and slap your mama green But now it's time to put some real pop into this and so of course since I've got green Well, obviously it's time to get out the pink And I knew I wanted to kind of cherry blossom feel to this teal and pink or turquoise and and You know sort of magenta and these kinds of green and pink colors just work really well together and they're all variations on the same sort of complimentary type of scheme and Boy oh boy does she have a lot of little leaves. I didn't even realize this until I started painting them all in But I want to really make sure that these stand out. This is going to be my Really intense color on the model and I want to make sure it's balanced all around It's a good chance to use an intense color because the leaves are so spread out all over the model I can go really poppy while still staying in balance And I can move up to something like the old rose here and really trace and create a lot of interest in these leaves Make them feel a little bit more like cherry blossoms while still maintaining the impact of the bright pink all over and you might think to yourself isn't tracing these three lines all Over every single leaf on this girl top and bottom a bit insane Yes Yes, it is it took um took some time But I think in the end it's worth it because it just looks really cool So you know sometimes you go the the extra smile Then I just took a bit of the pink and just kind of touched the edges of every leaf The goal here was to make sure again We're always creating that nice value contrast and little bright spots to keep the eye moving around the miniature Especially since the vines are nice enough to be in a wonderful compositional circle Because they're in that sort of a shape they do us a favor and so by having these bright spots all around We can make sure to keep the eye moving Let's talk about pop colors pop colors are the extra color you add into your Model that really only exists in a minimal way that needs to exist in a small balanced way around the model Now when you've got this sort of green and pink what else can you do but get into some turquoise And blue green So this was my choice here And I wanted to make the little bugs the little her Weapon which by the way could not be at a more odd angle for filming It's like directly under the vine turned at an odd angle vis-a-vis her and her face It doesn't show up in photos at all. So super fun placement on that spear really great a plus My only part of the model I really didn't like was the positioning of the spear and if I had my druthers I would I should have cut it And then repositioned it but hey didn't think of it at the time By building this up I'm working into Extremely bright poppy blues If if I did a lot of this if for example, I took her her armor that's now blacked out and did it with this color It would be completely overwhelming to the miniature You really have to be careful when you get into these bright poppy colors Not only do you need to watch and you know appropriately desaturate them Which I'm doing through these editions of white and gray where I'm you know increasing their tint To weaken them and weaken the saturation of the color But also notice that it doesn't really exist a lot. It's gems. It's her weapon.  So it's very small touches But having a really bright intense color But used in very small amounts again can help to complement The overall motion of the eye on the miniature keep it moving and keep it visually interesting providing additional tonal variation And most of what I'm doing here is just the same things you've seen me do in other videos working up sort of my standard non-metallic blue kind of crystalline crystalline weapon for her spear so on and so forth But the goal was to create something that was interesting Now this is my magic gold mix if you want to see this that video is linked up above It's too complicated to explain the recipe but you can watch that video and learn how to make it One of the most common requests I got is what do you do with that gold mix? Once you do can you highlight it and shade it and the answer is oh, yes And we will do so here and in attempting to show that I actually screw up This is a big mistake part I use rinox hide to shadow down this gold generally which works fine in most cases However, what I didn't contemplate here was that by using rinox hide, which is itself quite close to Wildwood and how I resolved the other wood patterns is I was actually making the gold look more like wood oops So by integrating a lot of the same colors I kind of make this whole model look like the armor is the same as the wood but slightly shinier Maybe that's a good thing. Maybe that's a bad thing. I'm not sure in the end how I felt about it I would love your opinion. Tell me what you think look at the final photos and tell me if you think I screwed up Um, but then I highlight it with just a little bit of pale burnt metal mixed in there To really pop the shine up catch all the edges things like that and with that She's all done There's the figure all done. We're going to roll it over the top here while I'm talking If you want to see how to make the base that was in a previous video you can find linked up above so go check that out Uh, I really hope you enjoyed this. This was a very fun very very fun miniature to paint and I really liked her She adds to my Sylvaneth army, which I'm excited about because I haven't had an occasion to paint anything for that army in several years If you liked this give it a like subscribe for additional hobby cheating in the future We have new videos here every saturday If you've got questions, I didn't answer drop those down in the comments below. I always answer every question If you want to take your hobby to the next level, we do have a patreon You can join down below focused on review and feedback and helping you along on your hobby journey You also get to be part of a great discord community full of enthusiastic incredible hobbyists So thank you so much for watching this one. I really appreciate it as always We'll see you next time You