WORKS FOR THE PROTECTION OF THE SEA-COAST AT CRANZ. 377 Works for the Protection of the Sea-coast at Cranz. (Deutsche Bauzeitung, vol. x., pp. 398–399.) Cranz is a village on the Baltic which has become a favourite sea-bathing resort. It lies 16 to 20 feet above the level of the sea, near a cliff of loamy clay, which the sea has been gradually washing away for years. Some twenty years ago a few short groynes were erected, and private landowners and the Administration of the Baths constructed some stone pitching on fascines, and protected by a few short piles. But these works were insufficient, the groynes not having been carried far enough back into the cliff. In the winter of 1873-74, in consequence of heavy storms, the rear of some of the groynes was washed out, and a strong current ran behind them, which broke away a great deal of the cliff. At the same time, the fascines having gradually decayed, the pitching sank, and the Corso, or seaside drive, was in danger. A sum having been voted for sea works, the following were carried out: 1. The existing groynes were largely strengthened and carried back well into the cliff, and new ones were added. The piles forming them are 13 inches apart, the heads being cut off at mean water-level. The groynes are carried out to a depth of water of 5 to 6 feet. 2. To protect a length of 575 feet of the Corso which is nearest the cliff, a substantial retaining wall of rubble masonry, 10 feet thick at the base and 4 feet 10 inches at the top, was erected, provided with a footing, also of rubble, which was carried down 3 feet below the mean water-level, and protected against wash by a close row of small piles, 3 feet 6 inches long, and by the foot of the old pitching. The top is dressed off with a gentle slope, which is turfed as far as the road. This wall cost £4 per lineal foot. 3. As it would have cost too much to protect the whole foreshore in the same manner, the remainder was provided with a longitudinal breakwater, filled with fascines. This consists of a double row of piles, 3 feet 3 inches apart from centre to centre, the front row battering at about 1 in 4 towards the shore, the rear row being vertical. The latter is driven about 10 feet from the face of the cliff, and connected with it by a row of piles driven at an angle of 45°, the heads being secured to those of the rear row. Each row is cut off 6 feet 6 inches above the mean water-level, and has a longitudinal brace bolted to the heads, with a cross brace under it tying the two rows together. Substantial fascines were placed at the bottom between these rows of piles, the rest of the space being filled up with loose branches. Two other free longitudinal rows of piles are driven in front of the breakwater, 6 feet 6 inches and 13 feet 1 inch respectively from it, each supplied with a longitudinal brace, a substantial plank driven horizontally into the sand at the foot, and a small stockade, the two latter intended to prevent the back wash. The piles are all 8 inches by 8 inches, from 10 to 12 feet long. The cost was £1 108. per lineal foot. The effect of these works has been excellent, as the groynes are mostly covered with sand to their tops, and a foreshore has been formed between the breakwater and the front row of piles. In the Author's opinion, groynes formed of single rows of piles some little distance apart answer better than double ones formed of close rows. E. D'A. New Quays and Docks at the Port of Amsterdam. (De Opmerker, Sept. 16, 1877.) The North Holland Canal having been opened on the 1st of November, 1876, arrangements are being made for large new docks and quays. The extensive cattle traffic with England necessitated a new jetty and stabling accommodation; and as, by terms of the contract, the canal must be deep enough for ships. drawing 23 feet on the 1st of November, 1877, it was incumbent upon the authorities to increase the size of the locks, which had only 19 feet 4 inches of water above the sills, when the level of the canal is 11.8 inches above A.P. A quay 1,300 yards long, 180 feet broad, and 5 feet above A.P. is in course of construction from the goods station of the State railway, parallel with the East Quay, and ending at the entrance of the Eastern Dock, leaving an opening of 280 feet, and forming with the East Quay a harbour for coasting vessels. The depth outside the outer wall will be 23 feet 8 inches, that on the inside 10 feet 6 inches. The usual method of dredging a channel in the mud to the required depth, and filling up with sand, was not followed. The depth of the Y at the greater part of the proposed quay was only 4 feet below ordinary level, but at the west end, near the dock gates, the depth is 39 feet, and it was resolved to form a wall by discharging sand from barges, and allowing it to displace the mud by its own weight. This was commenced on the west side in 1875, and continued through 1876; but the displacement was so considerable that, although 230,000 cubic yards of sand were discharged, no permanent ground was established above water-level. In 1876 the railway company commenced discharging on the east side; large quantities of mud were soon displaced, and firm ground formed, which could bear a double line of rails. Two parallel embankments of sand were then discharged in the direction of the outer and inner walls, and when it was found by boring that a depth of 24 6 to 26 feet below A.P. had been reached, the mud displaced, and that still remaining between the embankments, was utilised for filling, it having been found that its consistency after pressing and drying was sufficient. The outer wall in course of construction consists of a foundation of concrete 10 feet broad, resting on piles, from 8 to 20 feet below A.P., upon which a basalt wall 7 feet broad will be carried to 5 feet above A.P. Behind this basalt wall there will be one of concrete, also resting on piles 33 feet broad, and carried down to 8 feet below A.P., which is expected to give sufficient stability to the sand filling. There is also in course of construction a timber-harbour, provided with spacious jetties, quays, and sheds, with an area of 250 acres, intersected by sheet piling so as to break the waves and allow of the making up of rafts. Near the West Docks two jetties have been run out into the Y, each 400 feet long and 200 feet broad, and each resting on 4,750 fir piles 60 to 73 feet long. Other works of a similar character are sanctioned. J. D. L. Repairing Slip at the Hernösand Works. By V. M. STRÖM. (Ingeniörs-Föreningens Förhandlingar, Stockholm, 1877, pp. 4-5.) This slip was constructed for drawing up ships "broadside on,' and was so designed to provide for the large number of steamers which have to be laid up during the winter months. The level part, which is laid on shore, is about 240 feet long by 83 feet broad. On it nine steamboats of 120 to 140 feet in length can be laid up, or eighteen to twenty of 50 feet, these latter in two ranks. The inclined part, or slip proper, which is under water, is about 115 feet in length, and is laid with a gradient of about 1 in 8.3. The structure consists essentially of three lines of railway parallel to each other. Each of the side lines is laid with ordinary rails, with a gauge of 12 feet, and the distance between their centre lines is 71 feet. The middle way, on the contrary, has three rails on each side, viz., two flat-headed rails laid about 2 feet apart, and between them a rack; the gauge of this railway measured from centre to centre of the racks is 16 feet. Each rail is carried on a balk of timber 12 inches by 10 inches, laid longitudinally, and spiked to transverse sleepers, which, in their turn, are bedded on another set of longitudinal timbers. The three lines are held together by ties running through from side to side at intervals of about 12 feet, and the whole is stiffened with diagonal bracing. That part which is under water is covered with a flooring of planks, partly to prevent it settling into the bank on which it rests, and partly to carry the ballast for sinking it. The sea bottom is gravel and stone, covered by a stratum of mud, which increases from 5 feet near the shore to double the thickness at the outer end of the slip, where the water is 12 feet deep. The bank was made of earth and gravel, with a top layer of stone and sand close to the shore to prevent damage from the waves; during its construction the site was inclosed by a temporary breakwater. The carriage, upon which the steamers are drawn up, is of There timber, stiffened with cast-iron knees where the longitudinal and transverse pieces cross each other. It is about 16 feet long and 83 feet wide, and is carried on forty wheels or rollers, which run four on each rail, viz., one leading, two middle close together, and one trailing; those which run over the racks are grooved, so that they may clear the teeth while their flanges bear on the flat plates on which the racks are bedded. The axles are of Bessemer steel, and are calculated to bear a load of 500 tons with safety. Hinged to the edges of the carriage are twelve arms, six on each side, which can be moved into various positions in their planes of rotation by blocks and tackle connecting their upper ends to chains led from points in the centre line of the carriage. These hold the steamer like so many pairs of tongs, and serve to guide it into the proper position over the carriage before it is hauled up. are also six fixed arms on each side, projecting nearly horizontally outwards, which support the lower ends of the props by which the vessel is steadied. To insure the carriage moving square with the rails, the two end timbers are made to project about 6 feet. To the front end of each of these is pinned a casting, which can only move in a vertical plane, carrying an upright post which bears an index board. On a pin projecting from the front end of each casting is fixed a pointer, movable only in a plane perpendicular to that in which the casting itself can move. The lower end of the pointer carries a wheel, or grooved pulley, which runs along the outer rail of the slip. Thus, unless both ends off the carriage advance equally, the projecting pieces and castings above mentioned do not remain parallel with the rails, and vertically over them, and the pointers are deflected from the vertical, and from coincidence with the centre lines of the index boards which are behind them. The lengths of the parts are so arranged that when one end of the carriage is 6 inches behind the other, the tops of the pointers are moved 1 foot from the centre lines of the index boards. The hauling up is accomplished by three capstans, one at the end of each railway. The middle one works an endless chain, which also passes round a pulley at the lower end of the slip, and renders both a forward and backward motion possible. To hold the carriage on the incline, pawls are fitted to the underside, which fall into the racks. When a vessel is to be laid up for the winter, the carriage is sunk to the required depth, the ship is drawn over it, and guided into position by the arms and tackle already described; when it has arrived on the level part of the slip, greased slides and cradles are arranged under the keel. Upon these the vessel is steadied by props. It is then dragged off the carriage by the capstans and shored up in the usual manner, lying of course athwart the slip. By means of a lighter carriage running on one of the sideways only, a small vessel may be drawn out of the water and shored up on the slip in a single day. When the large carriage is used, about a day is required for the hauling up, and two or three more for finishing the work. M. L. The Waterworks of Aix-la-Chapelle. By J. STÜBBEN. (Deutsche Bauzeitung, vol. x., pp. 194–195.) The water supply of the town of Aix (now numbering about 95,000 inhabitants) was long a matter of great perplexity, owing to the peculiarities of its situation. It lies at a distance from any rivers or large springs, in an undulating country producing a multitude of rivulets, too small to be of much value. Some of these pass through the town and have become little better than drains. Others have been brought into it by pipes, but form a very insufficient source of supply. The matter is further complicated by the presence of the hot sulphur springs which feed the well-known baths of the place. The fear of disturbing these, and also the streams already utilised, precluded any attempt to obtain water close to the town. A scheme for damming the upper waters of the “Hohe Veen,” a stream about 9 miles to the south, and bringing a masonry aqueduct from thence to the town, was rejected on the score of expense. Finally it was resolved to seek a supply in some chalk hills which run through the district in long ridges from S.W. to N.E. The plan adopted was to drive a horizontal gallery into the chalk at such a level that the water when found might flow into the town by gravitation; and this has now been successfully carried out. The gallery (which is about 3 miles from the town) is about 6 feet 3 inches wide by 7 feet 3 inches high, and driven with a rise of 1 in 20. Ventilating shafts are provided at distances 820 feet apart, the whole length of the gallery being at present 3,770 feet. The supply of water obtained varies from 1,850 to 2,900 cubic yards per twenty-four hours. As this is not a sufficient supply, the gallery is to be driven a considerable distance farther. Pending its completion a well is being sunk close to the line of the gallery into the trough formed by a bed of slaty rock which runs through the chalk strata; and a 120-HP. engine is being erected to pump water from this into the aqueduct, so as to increase the immediate supply to the town. The water thus obtained from the chalk is of course somewhat hard, but is excellent for drinking, analysis giving only 2 parts in 100,000 of lime, of which only one-tenth is in the objectionable form of sulphate, the rest being carbonate. The pipes and other distributing arrangements are being made on the scale proportionate to the full supply. The water is first led in a channel of cement to a filter and service reservoir, and from thence to an open space just outside the town. From thence one line of mains runs in a complete circle round the outskirts of the town, and another is led diametrically through it to the opposite side, where it unites again with the first. Another reservoir is erected at this point, to equalise the pressure and give a special supply in case of fire, &c. The estimated cost of the whole works is £112,500. W. R. B. |