The Manchester Ship-Canal: Mersey Estuary Embankments and Other Works. Runcorn Division. (Including Plates at Back of Volume)

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42 WILLIAXS ON THE NANCRESTER SHIP-CANAL. [Minutes of

(Paper No. 21170.) ‘‘ The Manchester Ship-Canal : Mersey Estuary Embankments and other Works.-Runcorn Division.” By Sir EDWARDLEADER WILLIANS, M. Inst. C.E. THEestuary portion of the Xanchester Ship-Canal extends from its commencement at Eastham toRuncorn, a distance of 122 miles. Jn this length the canal passes along the southern bank of the River Mersey, about one-half being inland, while the otherportion is on the side of the foreshore, or crosses embayments ; embankments were therefore required to maintain the water in the canal at its proper level at low water. The preceding Paper deals with the embankments between Eastham and Ince, but the embankments between Ince and Runcorn were in the division of the canal of which the late Mr. Harold Abernethy, M. Inst. C.E., had charge ; and in order that the Proceedings of the Institution may contain a complete record of the mode of construction of the embankments, the Author proposes to describe the portion of the works superin- tended by Mr. Abernethy, whose early death has been a loss to the profession. The depth of water in the canal at the ordinary water-level is 26 feet, but as the lock gates and sluices at Eastham are opened when the tidereaches the ordinarywater-level in thecanal (whichis 14 feet 2 inches above the Old Dock Sill datum atLiverpool), spring tides give a depth of between 30 feet and 33 feet in thecanal from Eastham to Latchford, a length of 202 miles, At high water of all tides that rise above the ordinary level of the canal, which repre- sents a high neap tide, the lock gates and sluices at Eastham are closed, when the tidal water above ordinary canal-level is passed out into the Mersey through the large sluices at the River Weaver and at Randle’s Creek aboveBuncorn. Untilthe 7th February, 1897, thetide also flowed out of thecanal through three tidal openings at Ellesmere Port, the RiverWeaver and Runcorn; these are now all closed. In designing the embankments, the Author had to consider the pressure against them at spring tides during the construction:of

the canal, as theembankments had to acttemporarily as dams after the water between the embankments and the shore had been pumped out to enable the excavation of the canal to be proceeded with. The embankments had to be formed on foundations of silt, sand, gravel, clay orsandstone rock, and therefore varying designs were necessary, particularly at Ellesmere Port and at Runcorn. At the latter place, where the estuary is narrow, the Nersey Conser- vancy required a concrete wall to be substituted for an embankment in order to diminish the abstractionof tidal area near the Runcorn Bridge, which has three spansof 300 feet each, one-half of the span on the Runcorn side being taken for the canal and concrete wall. The material for the embankments, obtained from the cuttingson the canal, consisted principally of boulder clay;after this had consolidated, the slopes were faced withheavy dressed-stone pitching. The action of the tides on the clay, combined with the weight of the locomotives and wagons which conveyed the spoil along the top of the embankments, consolidated then1 quickly in a very satisfactory manner ; when the waterwas pumped out from withinthe embankments,to enablethe excavation to becom- menced, they proved to be watertight even at the highest tides ; though, as had been anticipated, there was slight leakage under them in some places, where either gravel or sand formed the base. Wherever an embankment was afterwards opened, it was found that the clay was SO closely compacted as to resemble the original beds from which it had been taken. In the detailed account of each embankment, it will he seen that trouble arose at some places where the foundation was of porous strata, but this was overcome by using sheet piling, and the total amount of pumping during the excavation of the canal inside the embankments was less than had been anticipated. The difference between high spring-tide level and the bottom of the canal was about 30 feet, but the pressure from outside ceased after the excavation was completed and the canal had been filled with water. At low tide less pressure has since existed, due to the canal being then kept at the level of a high neap tide. Temporary cross-dams were adopted at various points to reduce the risk of damage in case of the tide breaking in before the canal was filled; no such case, however, occurred. These cross-dams wereuseful in filling the canal, which was done in compartments,first by large iron pipes or timber shoots, and, as the water rose higher, by cutting through the dams. River Gowy Siphons.- The raisedwater-level of thecanal required siphons to be carried under it and the embankments, to

Downloaded by [ University of Sussex] on [12/09/16]. Copyright © ICE Publishing, all rights reserved. 44 WILLIAMS OX THE DIAX’CEIESTER SIIIP-CANAL. [Minutes of passland-drainage at places where low-lying lands werefor- merlydrained at or near low water, flap-doors keeping back thetide at high water. Thelargest of theseworks was con- structedto carry the River Gowy underthe canal at Stanlow Point. It consists of two siphons placed neartogether, each 12 feetin internal diameter; they are built of cast-iron seg- ments, the joint flanges being turned andrecessed ; they are inside the siphons, theintervening spaces being filled with cement so as to leave a smooth surface. Sixsegments were required to complete the circumference, andthey were so arranged as to break jointwith each other;the plateswere 1 inchthick, fastened by bolts lt inch in diameter. The siphons were laid in a heavily-timbered trench 50 feet below the level of the ground. Including the brickwork-chambers at each end, each siphon was 400 feet in length; they are 4 feet below the level of the bottom of the canal, resting on a bed of concrete 2 feet thick, which is founded on clay; 1 foot of concrete waslaid over theupper surface of the siphons. On the land side a pair of Stoney sluices are fixed to allow of either siphon being examined if necessary, and also to enable the whole ffow of the River Gowy to be concen- tratedthrough one siphonfor scouringout any deposit. The river has up to the present time kept the siphons clear without using the sluices. Ellesmere Port Embankment.-The method of driving the timber- piles throughthe sand-bank at Ellesmere Portis described in detail in the preceding Paper. The me of water under pressure was completely successful, and it is shown that timber-piling can be driventhrough sand even withgreater ease thanthrough ordinary soil. About 13,000 whole timber-piles were driven, the length of the sheeting-piles being 35 feet. At low waterthe embankment is free from leakage. The closing of the gap left in the Ellesmere Port embankment €or the passage of traffic was an interesting work. It wasfirst attemptedduring one period of low water. Many longtrains of wagonswere filled withclay and stoneready for tipping on each side of thegap, the quantity of material accumulated beingamply sufficient to close thegap if it could allhave been tipped before thetide reached high-water level. All went on well for some hours, when a locomotive got off the line and blocked the passage of the wagons, with the result that the tide broke through the dam before it was completed. It was then resolved to erect a high timber staging across the gap, and to tip the stone and clay from the staging in layers, allowing each tide

to flow over and consolidate it, the water being retained in the canal. This plan filled the canal gradually, and ina few tides the work was satisfactorily completed. The experience of the Author on the works of the Severn navigation,where it was necessary todivert the river into new channels and to raise the water-level untilit flowed over the weirs built in them, convinces him that a gradual lifting of the river- bed by materials that can resist the scour of the water over it, thusacting temporarily as aweir, is amuch safer planthan concentrating the whole scour of the river into a gap by tipping from each side. In one case on the Severn the force of the water when the river was thus narrowed carried away blocks of stone 10 tons in weight a distance of 100 feet. Weston Point Em.bankment.-The embankment from theRiver Weaver sluices to No Man’s Land, at Runcorn, is 14,100 feet long. Figs. 7, Plate 4, shows it commencing on gravel, afterwards passing through clay, but the greater portion is founded upon sandstone rock. This embankment was formed by tipping rubble-stone along the line of the foot of each side of the bank. From the tops of these stone footiags, grabs worked by steam-cranes removed the sand and mud down to the rock, when clay was tipped in to form the hearting of theembankment, which was protected duringthe period of consolidation by being faced on the estuary side with large blocks of stone roughly placed on the slope. After allowing time for the bank to consolidate, these blocks were dressed to form heavy coursed pitching for the faces of the embankment,the smaller stones being used on thecanal side of the bank. This embankment is much exposed ; it will be seen from Fig. I, Plate I, that it has to resist the full effectof westerly gales from the wide portion of the Mersey estuary between Garston and Weston Point. It has, however, in common with all the other embankments, withstood the heavy gales of several winter seasons without suffering damage. Riuw WeaverSluices.-The River Weaver sluices, like all the other sluices on the canal, areStoney roller sluices, and have, worked most satisfactorily. They wereconstructed by Messrs. Ransome and Rapier. The position of the sluiceswas fixed after borings had shown there was hard gravel and strong clay to found them on. They ‘were constructed inthe line of the embankment which at this point crosses the mouth of the River Weaver, its floods and tidal water beingpassed through thesluices, which are each 30 feet wide and ten in number, with a lift of‘ 13 feet, giving asluice area of nearly 4,000 square feet. The

Downloaded by [ University of Sussex] on [12/09/16]. Copyright © ICE Publishing, all rights reserved. 46 WILLIAJ-IS ON THE UASCIIESTER SHIP-Cbh’bL. [Minutes of sills of the sluices are fixed at the levelof low water in the estuary (which is about 163 feet above the bottom of the canal); they are of steel builtinto the concrete. The whole length of the foundations, 470 feet, was shut in by a half-tide dam of 12-inch sheet piling; cross-rows of piles were also driven at the ends, and across the dam in the centre line of each pier; the dam was 40 feet in width. This plan admitted of the work being carried on in lengths, the pumping-power being concentrated for each sluice separately, which allowed more rapid progress than by emptying the whole at each tide. After the sluices were erected, the outside rows of piles were cut off to platform level, the cross-rows being left standing up about 5 feet, forming a good dowel through the centre of the piers. AS soon as the excavation was taken out, the concrete platforms were built, 4 feet thick near the sills and 3 feet elsewhere; outside the front sheet piles large stones were used to prevent undue scouring action. Steel caissons of the exact shape of the piers, 36 feet long and 9 feet wide, were built into the concrete platforms; they are 9 feet in height, strengthened with steel cross-ties and filled with cement concrete on whichthe piers arebuilt. This modeof construction enabled the piers tobe rapidly brought upto half-tide level, when they were continued to their full height by masonry piers, the centre portion being concrete with blue-brick facing. Stop grooves are provided on both sides of each sluice, and steel shutter-pieces are kept on the ground so that any sluice can be easilyrepaired when necessary. Timberlattice-work is fixed across the piers on the estua,ry side to break the force of the waves in heary gales. The doors of the sluices are made of mild steel, strengthenedat the back byeight girders; they are counter- balanced by long boxes filled with concrete. A continuous-girder bridge rests on the piers, from which each door and couzlterbalance are suspended by four steel-wire ropes, passing over the gearing by which the sluices are raised by haud with ease by two men. They have now bcen working successfully for several years, even during severe frosts. Runcorn Concrete Wall.-The concrete wall which was built in place of an embankmentbetween No Man’s Land and the Runcorn lock, is 4,800 feet long. It will be seen by the section, Figs. S, Plate 4, that while a length of the wall at either end is founded upon sandstone rock, the middle portion is on coarse hard gravel. Thewall was constructedin cofferdams, the excavation being removed by steam-cranes, which also lowered the concrete that was deposited between two rows of sheet piling 22 feet apart;

Downloaded by [ University of Sussex] on [12/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] WILLIANS ON THE MAKCHESTEB SHIP-CAKAL. 47 pieces of stonewere embedded in the concrete. Thewall is vertical on the canal side; on the estuary side the upper portion batters so asto reduce thetop width to 16 feet. It hasstone copings, timber fenders being fixed along the whole length facing the canal. Embankment Locks.-It was originally intended toconstruct a large lock in Ellesmere Port embankment to enable shipping to pass in from the Mersey, butan arrangement was come to by which the traffic of the port was allowedto use the ship-canal from theEastham entrance locks. This saved thelarge cost of constructing and maintaining thelock, while the port has a better entrance than heretofore. Shipping of a size that could not have previously entered the port pays toll to the Ship-Canal Company. Weston Narsh Lock.-The estuary embankment from the River Weaverto Runcorn would,if made without locks, have closed all communication between the Mersey and its ports, unless the ship-canal was used; consequently the Weston Mersey, Bridge- water, and Runcorn locks have been constructed in the embankment. The Weston Marsh lock was built to give an entrance from the Weaver R’avigation to the ship-canal at a point in the River Weaver about 1: mile above the Weston Point docks. This lock is 229 feet long and 42 feet 8 inches wide. Adam was put across thecanal just above theWeaver sluices, andthe canal was opened for traffic between that dam andEastham on the 28th September, 1891, four years after the canal was commenced. The traffic from the Runcorn and Weston Point docks, as well as from the Weaver Navigation, was then enabled to use the ship-canal route to Liverpool while the embankment and the locks opposite those docks were constructed. Weston Xersey Lock.-The following particulars of the Weston Mersey lock will, except as to size, apply generally to the other embankment locks. Thelength between thegates is 600 feet, and includingpiers and approach walls is 2,790 feet. The width is 45 feet, and the depth over the sills 21 feet at ordinary spring tides. The lock is provided with five pairs of gates-two pairs at each end, one pair of which serve as flood- or storm-gates, and enable the lock to be worked whether the tideway or the canal is higher.The other pair are intermediate gates to shortenthe lock when the whole length is not used; the gates are of green- hearttimber, and are worked by hand-power; each hasthree sluices for scouring. Culverts run the whole length of the walls withopenings into the gate recesses andinto the lock invert; they are fitted with Stoney sluices. The lock walls are entirely

concrete, gauged 7 parts of graveland sandto 1 or' Portland cement, the facing above low-water level inside the lock being formed of 4 parts of gravel and sand to 1 part of Portland cement ; it is also protected by two continuous fender courses of Angleses limestone, projecting slightly from the face of the concrete. The approach walls and lock wall on the canal side have vertical and horizontal timber fenders ; the coping andquoins are of limestone, and the sills of granite; the foundation is rock. The time occupied in construction was only twelve months, deducting a stoppage in winter caused by frost ; the Author is not awareof any lock of the same size having been completed in so short a time. The site wasenclosed by a temporaryembankment, which acted as adam during construction ; the materialused was sandstonerock waste from the quarry, which stood without slips and formed a practicallywatertight dam with slopes l& to 1. Theouter slopes were covered with large blocks of stone, roughly placed, as a protection againsthigh tides and gales. Owingto the rock foundation, the earth dam was the best and the least costly that could have been adopted, and it allowed of railways being used, as the top was 20 feet wide; during a heavy gale in October, 1802, thedam was secure, althoughthe waves washedover its top, Theside walls of the lock wore builtin heavily timbered trenches, the middle part of the excavation being left until the walls reached the level of the foreshore on which the lock was constructed.A pumping-station, containing duplicate rocker-pumps 15 inches in diameter, waserected on the shore opposite the lock, and a heading was driven from the shaft under the bottom of the ship-canalto the lock. The concretewas mixed bysix Carey- Latham machines stationed at variouspoints along the work, and was deposited by skips worked by eighteen steam travelling- cranes. As soon as the walls reached the ground-level, the middle part of the lock was excavated and the concrete invert was put in, the walls beingcarried up to their full height in themeantime. The gate-platformswere completed early, so as to allow of the gates being built up while the other work was proceeding. They were put together at a slight distance from the hollow quoins and sill, to allow of the masons working, and were afterwards brought into their places by jacks androllers. Owingto the concrete (66,500 cubic yards) havingto be insertedquickly, a doublesystem of shutters was used, each 2 feet 9 inchesdeep, strongly made and strutted.The upright supports were placed 9 feet apart. The shutters were not struck untilthe next course of concrete was applied. Thusthe work

Downloaded by [ University of Sussex] on [12/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] WILLIBNS ox THE MANCHESTER SHIP-CANAL. 49 proceeded continuously, timebeing given for the lower course to set, when theshutters were drawnaway from the wall. Movable fillets were arranged on the upright supports, enabling the bottom shutters to be removed while the upper remained in position, thus preventing any injury to theface of the concrete by the shutters being dragged upwards. Bridgewater Lock.-The Bridgewater lock is 400 feet long and 45 feet wide. It was constructed byfirst bringing up the side walls to their full height by tide-work. Afterwards timber cross- dams were made across each end of the lock, when the invert and gates were put in. This method was adopted to save the expense .of a cofferdam round the whole work. After the water had been pumped out, and the invert partially completed, a westerly gale forced a springtide up G feet above the predicted height,the water rising to the top of the walls. The wall next the estuary stood well; but the inner wall, for a considerable length, moved forward at the point where the invert had not been built. When the tide receded, it was seen that the wall, although moved, remained nearly vertical, though it was broken into several lengths. On taking it down, it was found that the rock foundationwas adhering to the concrete wall (which was faced with blue brickwork) between 1 foot and 2 feet thick;and on examiningthe rock from which the wall had moved, a thin vein of saponaceous mar1 was found, which had been the cause of the damage, as the wall and the adhering rock had slid on it. The wall was rebuilt as before, after sinkinglower and taking out thelnarl, and the lock was completed without trouble, although other hightides occurred during theprogress of the work. Runcom Lock.-This lock, 250 feet long and 45 feet wide, was built in a similar manner to the Bridgewater lock without acci- dent. The locks are all of one width, though their length varies. The width was arranged so as to allow of barges passing at one locking lying twoabreast. The embankment and locks were expeditiously constructed, and praise is dueto the contractorfor the rapidityof their execution and the good quality of the work, which was rendered difficult by being in the tide-way, and also because arrangements had to be made to carry on the traffic of the adjacent docks by gaps in the embankment or otherwise during construction.

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