MULBERRIES By D. H. LITTLE MY first contact with "Mulberry" took place a week before Christmas, 1943. Sir Arthur gave mc a set of drawings of some floating break waters with instructions to report on how suit able they might be if subjected to storm waves eight feet high. I was warned that the job was Top Si cri t and that no more men than abso lutely necessary, were to deal with it. From that day until "D" Day the only people who bandied Mulberry in the Drawing Oflicc were Mr. E. Evans (now resigned), Mr. Minni- kin (now with the Superintending Civil Engin eer, Bristol) and myself. Outside the Drawing Office, Sir Arthur and Dr. Chatley (now re signed) were the only engineers involved, while all the papers were filed by Mr. Gervase Rendell personally. (I have no strong recollection that the filing system adopted was very original but all the entries were in manuscript and most legible.) At that -very first contact, none of us in the Drawing Office had any idea what Mulberry stood for, but the drawings were marked Phoenixand showed large box-like struc tures of reinforced concrete in outlinesome thing like shoe boxes without lids, and divided up inside with cross walls after the style of egg boxes. There were four different types- all about 200 feet long but of varying heights and widthsthe smallest being 25 feet high and weighing 1,660 tons, and the largest 60 feet high and weighing 6,000 tons. They were in tended to be towed across the sea and then sunk in pre-arranged lines so as to form a sheltered harbour in which ships could lie at anchor and be protected against stormy seas. Such structures are by no means novel and permanent commercial breakwaters have been built all over the world on similar lines, except that invariably the hollow caissons-as they are usually termedare filled with sand, as soon as they are sunk into position, to give them appropriate weight and strength. We under stood, however, that the caissons we were now concerned with were not going to be filled, and our calculations soon indicated that in waves eight feet high they might rock badly. This was rather an alarming conclusion. The job was obviously an extremely important one, and although there were no designers' names on the drawings it seemed reasonable to assume that important people had been responsible. Before stating officially, therefore, what we thought, we tried to find out a little more about the original designers. We were not successful in this, and so with a hectic last-minute rush a report left the Department on Christmas Eve stating that in our view the structures were not strong enough as a whole for their purpose. This was intended to draw blood, which it certainly did. Two weeks later 1 accompanied Sir Arthur and Dr. Chatley to a very high-level meeting in London at which Admirals and Generals were in the majority. At this meeting I realised that Mulberry was the code name for com plete new harbours with port facilities to be built oil' the French coast for the invasion, and that Phcenix was the code name for those units which were to form the fixed break water protection to the harbour. As a result of this meeting we had close consultations with the Army Engineers, who had designed Phoe nix," and we agreed that while the waves would almost certainly cause them to rock, it was unlikely that the blows would last long enough to topple them right over. We were firm in our view, however, that the units might be pushed bodily along the sea bed, and accord ingly it was decided(a) that an attempt should be made to add sand to them when in position, and that the breakwaters as a whole should be strengthened by sinking ballasted block ships in line in front of them. There was no possibility by then of amending the design because many units all over the country were well advanced in the actual making. Later on when details of construction became available we suggested some simple but very important adjustments to the steel reinforcement of the outer walls, and these were adopted in the last units to be built. In the main, the various components such as breakwaters, pier heads, jetties and roadways which went to the making of the Mulberry harbours were the responsibility of the Army, who arranged with teams of private designers and contractors for the design and building of them in this country. Two harbours were planned and actually built Mulberry A and Mulberry B. Both were built from similar components, made mostly by the British, but Mulberry A was assembled and constructed on site by the Americans for the U.S.A. Army, while Mulberry B was put together by the British for our Army. n

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Watersnood documentatie 1953 - diversen | 1949 | | pagina 1