We are in September 96 a few hours before my working week stops. I’m finishing a little intervention in a French river when suddenly my beeper informs me that I have to call my boss. Shit, that will probably mean that the nice week end I had planned to spend with my lady will be fucked off. Indeed, having found a telephone booth in the nearby village my company informs that they have received a call from a big French company who was actually driving a tunnel in Berlin. They had a problem with the progression of the TMB and were asking our assistance to perform some cutting and welding in the shaft. Having never visited this city, I immediately accepted the offer to go there and proposed to contact two other guys to come with me. The next morning together with my colleagues Jürgen and Jean-Michel, we are on the road to the site where we are expected to start work the same evening. The journey to Berlin was uneventful and at the stroke of 8 pm we were in the engineer’s office ready to hear the nature of our work. He explained us that we had not to work in water but instead in the dry and under pressure in the front part of the tunnel boring machine. This kind of big machine, somewhat identical to that which dug the channel tunnel is pushed into the soil by enormous hydraulic jacks while a large rotating cutting wheel excavates the ground in front of the shield.
This kind of big machine, somewhat identical to that which dug the channel tunnel is pushed into the soil by enormous hydraulic jacks while a large rotating cutting wheel excavates the ground in front of the shield. The Berlin soil was mostly composed of sand and up to now the tunnel had already progressed over a length of 3 km without problem but since a few hours the machine refused to move. During their investigation, the engineers had discovered that what was blocking the progress of the elements was neither more nor less than a piece of rock. Knowing what was preventing the advancement was one thing but now that piece of rock had to be broken and evacuated. As you can imagine it’s by no way possible to go outside the shaft to do the demolition. No, the only manner to have access to it was to cut a window out of the shaft just above the stone. Doing such a cutting at atmospheric pressure would have presented no difficulty and despite the thick steel wall of the shaft would have been realized in a few hours. But in the present case, the working pressure was 3.2 bar (kg/cm²) which can be compared to a water depth of 32 meters and thereby the risk of fire could be high. Indeed, as every diver knows when the pressure increases, the partial pressure of the oxygen in the ambient air we breathe also increases which has as a consequence to accelerate the combustion of things. Knowing that, you immediately see that the use of a classical burning torch or a Broco torch was not the adequate solution because the supply of oxygen would quickly increase the percentage above 25% and so increase the risk of a deadly flash (such an accident took place in Belgium a few years earlier, causing the instant death of all persons present in the shaft). The steel wall we had to cut was 6 cm thick and to avoid the risks mentioned above I opted to use an arcair gouging torch with carbon rods what in those years was one of the less dangerous ways to work. But even if I used air instead of oxygen there remained a risk of fire and therefore I required that a tender equipped with water lance should be ready to intervene at the slightest alert during the cutting process. Being the team leader, I proposed to do the first shift to start jobs that I estimated would last for approximately 72 hours. Pressurizing took place without problems and once at the required depth my tender and I passed to the other side of the airlock where I had to work.
The exact position of the cutting had been marked by a previous team and so I could rapidly install my burning gear. The place was quite cramped and therefore I proposed to my German assistant to stand on the small bridge we had just used to pass the sas. I was now ready to start, to avoid burns due to the projection of molten metal I had fully dressed myself with leather clothes. Of course, gouging such a thickness is relatively slow and I need to pass into the kerf many many times to blow the molten steel away. I’m now cutting for about one hour and have reach a point where I need to lay on the bottom to have a better access to the line I have to cut.
But the bottom is covered with a thick layer of bentonite mud which means that if I lay myself down, I will immediately get soaked through and therefore increases the risk of being electrocuted. What to do? Not difficult: I asked my tender to pass me one of the integral raincoats that is hanging outside the sas. Equipped with it, I can now lie down in the mud and resume my cutting. I was cutting again without a problem for about 10 minute when suddenly I could see that the inside of my welding helmet reflected flames that came from somewhere else than my cut. Strange I thought, so I ceased my cutting, lift my visor and Horror! Saw that my left leg was burning. Immediately I tried to extinguish the flames by tapping them with my leather gloves while that at the same time I was expecting to receive a jet of water from mate. But nothing came. Fucking hell what is that con above me waiting for? While screaming I stood my head and 'Help', saw that there was nobody on the stage. I could now feel that the fire had progressed and had probably consumed a part of my leather pant because all of a sudden, a sharp pain irradiated my knee. Desperately I still continued to tap the flames but without result, my pant continued to burn. As I did not want to completely finish like a living torch, I did the only thing that I had to do. Make a roll, turn myself and plunge my leg in the mud. The effect was immediate, the flame died while that at the same time I received a shower of cold water coming from above me. You stupid bastard, where were you? Why have you not react immediately? My assistant was really confused, he did not know what to say to apologize. What had happened? In fact, he had simply passed into the airlock for a drink at the time where the incident happened. All this would not have happened if he had informed me course I would have stopped to cut for one or two minutes. Anyway it was too late my raincoat left leg had completely melted away and my leather pant had been badly attacked by the flames but was still covering my knee preventing me to see the gravity of my injury. Anyway, the shower had entirely soaked me from feet to head and so no more question to continue to work in these conditions and thus my German informed the surface of the accident via the internal phone. As it could be foreseen the surface at her turn informed us that we had to enter the airlock for decompression. Luckily, our time under pressure was nearly over, only twenty minutes more to go thus I presumed that the client would not complain too much for the lost time. The decompression lasted some 100 minutes, which left me time to undress me and look at my wound. Oh! Yes, not bad at all. I had a nice wide second degree burn. To mitigate the effects of pain and clean the wound, I asked for a few bottles of icy water. During the decompression, my companion was still very sorry about what had happened, but in fact the great part of responsibility was on my side because I should have remembered that a rain suit is by no way a fireproof cloth. The decompression went on without problem and at the exit a doctor was already waiting for me. His diagnosis was pretty harsh because he considered that the injury was serious and he advised me to return to Belgium. I immediately could see that the project manager was a bit upset by this decision because it meant that in this case I would take my two colleagues with me and leave him in a difficult position. So I refused his advice and decided to stay. To avoid infection, the doctor advised me to put a watertight bandage on my knee before every shift and no need to say that I followed his advice to the letter. But despite this, my leg made me suffer because I had a lot of trouble to bend my knee. As expected, the cutting of the window took another 3 days followed by a few hours to hydraulically burst the boulder. Once that first part of the mission completed, we stayed two more days to make some welding work on the TMB teeth and at the end of the week our job was entirely finished.
Despite the incident, the client was very satisfied with our service because they could now resume their progression and so to thank us he made us discover Berlin by night.
Sometimes we believe to have made a correct JSA that covers every hazard and we forget what is obvious.