The Hardinge Bridge Over the Lower Ganges at Sara.” by Sir ROBERTRICHARD GALES, F.C.H., M

1s GALES ON THE BARDINGE BRIDGE [Minutes of

20 November, 1917. HARRY EDWARD JONES, President, in the Chair.

(Paper No. 4200.) ‘‘ The Hardinge Bridge over the Lower Ganges at Sara.” By Sir ROBERTRICHARD GALES, F.C.H., M. Inst. C.E. THEHardinge Bridge connects the standard 5-foot 6-inch gauge system of the Eastern Bengal Railway south of the Ganges with themetre-gauge system north of theriver. It comprisesfifteen girder spans of 345 feet 13 inch, with three land spans of 75 feet at eachend. It carries a doubleline of standard gaugebetween thegirders and a footway 5 feet in widthbracketed off the down-streamgirder. The extension to the northern bank of the standard gauge has necessitated the conversion thereto of portions of the metre-gauge system (Fig. 3, Plate 1). A proposal for bridging the Ganges at Sarawas first put forward officially by the Administration of the Eastern Bengal Railway in 1889. Thereference resulted in the appointment of acommittee which, after consideration, outlined the chief dangers to be feared and reported a bridge to be feasible. In 1902 the preparation of a detailed project was entrusted to Sir (then Mr.) F. J. E. Spring, K.C.I.E. A controversy having arisen as to the best site for the bridgefrom a commercialpoint of view, this was referred t,o a committee in 1907, which recommended that the bridge should be built at Raita. Some doubt remained as to the suitability of the Raitasite from atechnical point of view, andan engineering committee was appointed in 1908 to consider this. The committee, withoutminimizing the danger and diaculties of theproject, expressed the opinion that a bridge could be constructed at Sara with freedom from excessive risk. The changeable character of the channel, the instability of the banks, and the great rise and fall of the river at the beginning andend of therains, combined with the existence of themetre

gaugeon the northern bank and the standard gauge on the southernbank, had by this time rendered the transhipment in barges and wagon-ferries of thegreat and rapidly increasing volume of traffic, mainly in jute, tea and seeds, so difficult from the point of view of the Railway Administration and so unsatis- factoryfrom the commercial standpoint,that the demandfor a bridgewas acute. The Author was appointedEngineer-in-Chief of the project, andHis Majesty’s Secretary of Statefor India sanctioned the construction of the Lower Ganges bridge at or near Sara in December, 1908. SITE. The bridging of the Gangesat Sarainvolves three main considerations, namely, the security of the approaches, which may be &ken to be the line from Calcutta to the bridge on one side, and from the bridge to Santahar on the other, the stabilizationof the course of the river in thevicinity of the bridge, and thebridge itself. The country between the Rajmahal and Garo hills and the head of the Bay of Bengal is a deltaic formation deposited mainly by the rivers Ganges andBrahmaputra ; it is stillextending seaward. The earliest published information with regard to the course of the numerous rivers which traverse the delta is obtainable from the maps of the Bengal Atlas compiled from the surveys of Major James Rennell, the firstSurveyor-General of Bengal,published in 1781 (Fig. 1). Muchinformation and some interestingspeculations are to be found in a Paperby Mr. JamesFerguson, F.R.S., on “Recent Changes in the Delta of the Ganges,” published by the Geological Society of London.’ The greatest change which has occurred since thedate of Major Rennell’s maps is the abandonment by the Brahmaputra of its course to the east of Dacca, and its occupation of the course of the river Jenai, to join the Ganges at Jaffiergunge, near the present-day Goalando, involving a maximum translation westward of about 70 miles. No great change has occurred in the general course of the Ganges since the publication of the maps, and itis necessary togo back tothe sixteenth century for the last considerablealteration in the course of this river, which is thus alluded to in the ‘‘ Imperial Gazetteer of India, Bengal” : “ Proln thedawn of history till probably some time in thesixteenth century the Bhagirathi formed the main ’stream of the Ganges ; and in theeyes of Hindus this, and not the Padma (LowerGanges), is still the sacred stream.” Thus, in the early part of the sixteenth

Journal of the Geological Society, vol. xix, 1883. c2

century,the Ganges flowed alongthe western edge of thedelta (Fig. 2) andthe Brahmaputra through the country to the east. Thecentral part of thedelta was occnpied by thegreat rivers Mahananda,Atmi, Kamtoya and others flowing southward from the Himalayas, possibly as separate rivers, into the Bay of Bengal. In thesixteenth century the Ganges broke across the lineof flow

Fig. 1.

DELTAOF THE GAKGES,1781.

of theserivers to the south-east, and in the early part of the nineteenthcentury the change described above occurred inthe course of the Brahmaputm. These changes, it is believed, occurred gradually, that of the Brnhmaputra probably occupying a period of 20 years, from about 1805 to 1825. Borings taken at river cross- ings OP theline of theSara-Serajgunj Railway show that the

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] OVER TIIE LOWER GABGES AT SASA. 21 underlying clay,which extendsfrom Sua and probablyfrom Charghat at the mouth of the 13aral to the Dilpussur, disappears there ; and this may indicate that the last change in the Brahma- putra was areversion to a still older channel during the earlier occupation of which this clay. hadbeen eroded and removed. There is a strong probability that this older channel is that which

Fi,y. 2.

RAJMAHAL"

MURSHIDAB

MRISHNAGA

MILES SO

COURSEOF THE GANGESRIVER EARLY IN THE ~GTHCENTURY AND PROBABLE MUCH EARLIERCOURSE OF THE BRAHXAPUTRA RIVER.

can still be traced under the name of the Ichamutty from east of Bogra through Pabna, crossing the present Ganges at right angles, and passing to the west of the Eastern Bengal Railway, which it recrocses at Shibnibash, whence it flows into the head of the bay, The condit,ions obtaining at the present time (Figs. 3, Plate 1) me as follows: from the right bank above the bridge-site take off

arethe three Nadia rivers, the Bhagirathi, the Jalangi and the Matabhanga, which combine to form the Hooghly, on which stands the city of Calcutta. On the left bank the Bard leaves the main stream at Surdah and flows into and through the depression of the Chalan Beel to join the Brahmaputra at Bhera. Below the bridge- site the Gorai, an important offshoot, leaves the main river near the town of Kushtia on the right bank. All these rivers increase or diminish in size in accordance with local changes in the course of the main river, increasing when their off-take occurs on a concave bendand diminishing when it occurs onthe convex side. They have, however, alldiminished in size sincethe preparation of Major Rennell'smaps, andin the case of theNadia rivers this diminution is so marked that the bar at the off-takeis dredged every year by the Bengal Government to keep navigation open for boats and steamers in the dry season, and the deterioration of the Hooghly, which has silted up considerably in the upper reaches, is now a matter of Governmentinquiry. The Gorai at the present time is increasing in size owing to a change in the main river and theestablishment of a fresh off-take. TheBard appears to be controlled to some extent by the Brahmaputra. The Brahmaputra rises about a month earlier than the Ganges, owing to the advance of the monsoon rainsbeing through Burma and westward along theHimalayas. The rise of theBrahmaputra dams back the water of theChalan Beel, in which the Ganges waterfrom the Baral distributary deposits its silt, and the Beel is being rapidly warped upand brought under cultivation. The Bard is at presentdiminishing in size, andthe railway-bridge crossing it has lately been shortened during its reconstruction by the Railway Administration. The Bengal delta consists for the most part of a fine micaceous sand, extending to unknown depths, with overlying layers of silt easilyeroded by thegreat rivers. A hard,inerodible red clay known as the Borindoccurs, however, in the left bankof the Ganges as far south as Burgachee above Rampur-Boalia, whence it extends northward. A similar clay occurs at Phudkipur on the right bank nearRajmahal, w'here it is formed bythe disintegration of the basaltictrap flows of theRajmahal Hills. The clay of theMad- hupurJungle, in the Mymensingh and Dacca districts,appears to have similar characteristics, and the great change in the course of the Brahmaputra may be attributable to a gradual upheaval of theMadhupur Jungle surface level. Withthis exception the only material in the delta capable of offering serious resistance to erosion by water appears to be the Sara clay, a black sedimentary

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] OVER THE LOWER GANGES AT SARA. 23 depositcontaining small shells andtraces of ricepeat. Clay also occurs at Raita, and the existence of the Raita and Sara clays has been the cause of the comparativestability of theriver in the vicinity of Sara (Fig. 7, Plate 1). As may be seen from the foregoing, the delta of the Ganges has notyet attained complete stability; changes, however, occur but slowly, and the effect of suitably aligned railway-embankments in fixing the regime of therivers appears to beconsiderable. For this reason it is highly desirable that the necessary through railway connection from Gopalpur via Rampur-Boalia to Nachoul on the Katihar-Godagari Railway, with a bridge near Charghat, involving control of the Baral, should be made as soon as possible ; and that the proposed linefrom Sainthia via Berhampur to Bhairamara, givingdirect connection between the Bengal coalfields andRaj- mahal stone-quarries and Northern Bengal, and affording a direct route for the considerable coolie traffic to Mymensingh and Sylhet, should also be undertaken. Thecontrol of theBaral and of all spillsbetween Sara and Santaharis of the firstimportance. For if the Gangesbroke through by way of the Baral or of the low land on either side of

' it intothe Chalan Beel depression, the bridge would not onlybe rendered useless, but a newone would haveto be built.Fig. 4, Plate 1, shows to an exaggerated scale, on the arc of a circle struck from Rztjmahal and passing through the bridge, the great depression of the Chalan Beel and high-flood level at the bridge relatively to the level of thecountry on both banks of theriver. Any other line of levels, as in Fig. 5, Plate 1, alongthe alignment of the Eastern Bengal Railway, which intersects at thebridge the circular arc on the surface of the deltaic cone, creates a false impression of relative levels. An increase in any of the Nadia rivers would not be so serious. For if the whole Ganges took this route, although the bridge at Sara would be rendered useless, no fresh bridge would be required to connect Northern Bengal with the port of Calcutta, alwaysprovided that the port of Calcutta in such a contingency could be retained on its present site or be rebuilt at Port Canning or other inlet eastward. The facts having been established that all spills above Sara are diminishing in volume, and that no very rapid changeof conditions is to be anticipated, and since the subsidiary lines sketched above will probably be undertaken for traffic reasons in the near future, it was considered safe to proceed with the construction of the bridge. The site is subject to earthquakes and cyclones, Location.-The friable nature of the natural banks required that

permanent artificial banks should be constructed before any bridge could be built with safety. The determination of the precise site was largely governed by this consideration and by the necessity of avoiding any site which would interfere with the existing arrangements for the transhipment of goods. Facility of construction had also to be taken into account. Previous surveys had shown that a depth of 100 feet below low-water level might be expected at and along the Sara clay for a considerable distance. The river showed a tendency to return to the bight above Raita with n consequent widening of the river towards the northbelow that point. A site 24 miles below Raita was considered but was rejected for cogentreasons, anda site 3 miles below Sara was selected. Its advantages are that its position below theSara clay on the left bank practically ensures immunity from the dangers to which the left guide-bank at the upper site would have been exposed, whilst the existence of Raita point and the course of the river below it appearto provide similar security for the right guide-bank. The shorter guide-banks necessaryat the lower site, in view of the above considerations, afforded greater probabilityof successful construction in oneseason, with some savingin cost. Further, practical immunityfrom disturbance of existingconditions is secured in respect of the RailwayGhats :bt Saraand Damukdia, any inter- ference with which would paralyse the Eastern Bengl Railway ; a shortening of theSerajgunj branch is effated, bywhich an important additionof jute and other traffic will be gained ; and. finally, the widening of the Raita peninsula by about 2 miles leads td the removal of the right approach from danger of attack by the river below thebridge. The possibility of the left approachabove the Sara claybetween Saraand Gopalpur being attacked has, it is believed,.beenobviated by thestrengthening of theSara clay at Sara and the retiring of the alignment from the river as far as the configuration of thecountry permitted, whilst there are good groundsfor assuming that, so longas the discharge passing the bridge-site remains what it is, the river will not again attain the extreme curvature shown on Major Rennell's maps above Raita on the right bank and above Sara on the left bank. Nevertheless, as the river may again work into the Lalpur bight and threaten the line at Gopalpur, it is of the greatest importance that the formation-level of the line in the vicinity be raised so that the railway administration may be in a position to meet such an attack;or that on the construction of theGopalpur-Nachoul connection theopportunity be takento construct a continuous embankment adjoining the railway-lineat least 2 feet 6 inches above

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedi11gs.I OVER THE LOWER GANGES AT SARA. 25 high-floodlevel fromIshurdi to Gopalpur.The relative levels of high flood and the present railway-embankment areshown in Fig. 5, Plate 1. TRAIXING-WORKS. The training-works are designed to prevent lateral movement of the river at the bridge, and to obviate any considerable change in the course of the river in its vicinity. Since 1868 the Ganges has slowly moved eastward at the bridge-site about 12 mile, and before the construction of thetraining-works this movement was pro- ceeding at the rate of about 200 feet ayear. Since Major Rennell's survey in 1764 there had been erosion of the Sara clay amounting toan eastwardmovement of theriver there of about f mile. AtRaita the clay hid beenalmost entirely eroded, and it wi4.s evident that as soon as its removal was conlplete there wouldbe nothing to prevent the rapiderosion of the Raita peninsula and the advance of the great bend of the river upon the right approach of the selectedbridge-site. The works undertaken to arrest these movements, and to restrict the river to the oscillations above Sara and Raita which have occurred in the immediate past, consist of a pair of stone-pitched guide-banks at the bridge, and the revetment with pitching stone of the clay at Sarn and Raita. The works are connected with the main lineby suitable branch sidings for purposes of inspection and maintenance. The pair of banks fianking the bridge (Fig. 10, Plate 2) are aligned at right angles to the bridge and are t,ermed the Right and Left Guide-Banks.They .are each 4,000 feetin length, extending for 3,000 feetabove and 1,000 feet below the bridge, with suitably curved ends. They consist of'a core of sand protected on the river face with 1,250 cubic feet of pitching per lineal foot of bank. The stone is arrangedas a revetment (Fig. 15, Plate a), ranging from2 feet thick at the top to3fr feet thick at the toe of the bank, on layers of quarry chips and clay. The remainderof the stoneis deposited in an apron extending outwards from the toe for a distance of 150 feet in three belts of 50 feet, respectively4 feet 6 inches, G feet 6 inches and , 8 feet 6 inches in thickness. The design provides that, as the river cuts away the sand from under the outer edge of this apron, the stone falls in and automatically pitches it slope in cont>inmtionof the slope of the bank to a depth of 100 feet, the maximum known depth of bendscour. At the upper and lower ends of the guide- banks the pitching is carried round to the back of the bank. The banksare 18 feetabove high-flood level, andtheir upper part is pitched with the heaviest stone available, as a, protection against the

very considerable waves which maybe expected in a cyclone blowing up-stream with a fetch which may be as much as 10 miles. Theclay at Sarahas beenproved by borings toextend from Dhapari,north of Sara,to Paksey, about mile above the left guide-bank.The clay,which unfortunately is not of uniform strength, is found to a depth of about 90 feet below high-flood level at the bank of the river, thinning off to 40 feet at a distance of a mile inland. The clay is eroded by the action of the river on the sand beneath it, and, falling in,is washed away. The revetment provided at Sara extends fora length of 3,650 feet and consists of 650 cubic feet per lineal foot deposited in the water to overlap the offoot the clay and arrest the eroding action described above. The clay at Raita is of comparatively small extent and the headland is revetted for a length of 4,000 feet, 2,000 feet on the northern and 2,000 feet on the western face, connected by an easy curve, to protect the clay from attack from the westward should the river again occupy the Sonaikundi Bight, and from the north should it retain its present course.

MAIX FEATURESOF THE BRIDGE. The drainage-area of the Ganges above the site of the bridge is 361,000square miles. A maximumhigh-flood level at the site, of 50 feetabove mean sea-level atKarachi, wasestablished after thorough investigation. A gauging by the Mississippi method taken on the 22nd August, 3910, with a flood-level of 47.77 feet, showed a discharge of 1,926,080cubic feet per second. This is probably one of the largest discharges hitherto gauged by exact methods in the mainchannel of any river. Four gaugings in all were taken, and a curve drawn through them when plotted showed a probable discharge of 2,500,000cubic feet per second at maximumhigh- flood level. Fig. 6, Plate 1, is R water-leveldiagram for 7 years. The maximum rise of flood is 31 feet. The surface slope in flood at the bridge was found to be 0 * 36 foot per mile, and at low water 0.10 foot per mile. The maximum velocity in flood recorded before theconstruction of thebridge was 12.8 feetper second witha meanvelocity of 9.34feet per second. The sectional area of the riverin maximum flood, excludingspill over high banks, was 254,750 square feet. Although the Ganges in many places has a flood width of several miles, it was, at the siteselected, for all practical purposes contained in a single channel, the old channel on the Bhairamara side having silted up at its head at Bahadurpur to within a few feet of high- flood level, The width of this single channel, from the steep bank

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. pr~~ee4w.3 OVER THE LOWER GANGES AT SARA. 27 on the Sara side to a definite rise on t,he right bank, which afforded reasonable prospect of the construction of the right guide-bank in one season, was about 5,400 feet; and a bridge of fifteen spans of 359 feet from centre to centre of ,the piers, or 5,385 feet in length of main spans, being assumed, it remained to be ascertained if this amount of waterway was sufficient, allowing for the obstruction of piers and guide-banks.Deducting from 5,385 feet 180 feet for slopes of guide-banks, and 518 feetfor fourteen wells, a clear waterway of 4,687 feet is obtained. A width of 4,687 feet, marked off onthe remarkably even section atthe bridge-site of 1910, showed a mean depth of 50 feet at maximum high flood. Assuming, for the purpose of calculation, an even depth of water a.cross the bridge at high flood, and a depth and velocity due to a surface fall of 43 inches per mile, it will be found that a depth of 70 feet and a mean velocity of 8 feet per second will rather more than pass the maximum discharge. No sucheven distribution of water can be expected, and even in 1910, on the 22nd August, with a flood-level of 47-77 feet anda maximum depth of 51 feet, a surface velocity of 12 -8 feet persecond was recorded. So long as the river is maintained in its present straight alignment above the bridge no great variation in depth andvelocity seemed probable, but if the course of the river should he changed so as to impinge in a bend on the guide-banks, a similar depth of 100 feet below low water or 131 feet below high flood might result, as was recorded at Sara when those conditions existed. It seemed desirable,however, to bridge the riverfor normalconditions in a straightreach, where it waspractically confined in one channel, in preference to attempting by contraction to force it to great depths, although the possibility of great depths of water wouldneed to be provided forthroughout. A bridge of fifteen spans of 345 feet l.$ inch from centre to centre of bearings was therefore adopted, with a land span of 75 feet at each end to pass the track on the guide-banks, subsequently increased to three land spans of 75 feet from centre to centre of bearings at each end of the bridge (Fig. 14, Plate a), in order to relieve the abutments of thethrust of the bank.The overall length of the bridge is accordingly 5,894 feet. A maximumdepth of bend scour of 100 feet below low-water level having been obherved at Sara, and as borings showed nothing but fine micaceous sand in the river-bed, a depth of 150 feet below lowwater was acceptedas sufficient inthe openriver for well foundationssurrounded with pitching-stone. Forthe two foundations, Nos. 2 and 15, immediately outside the guide-banks, where the greatest scour might be expected,a depth of 160feet was

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 28 GALES ON T’IIE IIBRDlNGE BRIDGE [lllinules of prescribed. A headway for navigation of 40 feet abovehigh-flood level was adopted in consultation with the steamer-companies. It was originally intended to construct the piers for a double line and to erect at first girders for a single line only. The cyclone of the 17th October, 1909, however, demonstrated that the bridge was within the cyclone area, and, in view of its exposed position, it was then decided, owing to the greater shbilitywhich could be obtained with the greater width of span, to design the bridge for a double line in the first instance. This also appeared to be justified by the traffic prospects. COSSTRUCTION. Preliminaries.-The earlypart of 1909 was occupied in preliminary surveys and investigations ; prospecting for the supply of stone ; arranging for locomotives and rolling stock of both standard and metre gauge, as well as standard- and metre-gauge track for service-lines at the quarries and at thebridge ; chartering steamers and flats to handle the large amount of pitching-stone and other materialrequired ; acquisition OF land : starting brick-fields, and the provision of steamers, launches andbarges. Thereafter building quarters for staff, hospitals, workshops, power-houses, water-supply and other service works on both banks of the river, and medical andsanitary arrangements, were put in hand.There wereeven- tually in use onthe operations 81 miles of standard,metre and 2-foot B-inch gaugeservice track, and twenty-four locomotives, twenty-eight brake-vans and 830 trucks. The existence of direrent gauges on the right and left banks ancl the difficulties of transhipment across the river, complicated these preliminary arrangements, and materially affected the programme of works. Supply of Stone.-Owing to the absence of stone in the vicinity, and to the difficulty of burning clay in the quantities required and obtaining thereby a reliable product, it was necessary to seek far afield for quarries for pitching-stone. Xxcellent trap quarries were eventually obtained at Kotapara, near Pakur, on the loop line of the East Indian Railway,334 miles distant by rail, and at Phudkipur, near Rajmahal, 134 miles distant by water; and quarries of mixed boulders atJainti, 219 miles distant by rail. Stonesweighing from 65 to 165 lbs. were accepted as standard pitching-stone. The quantity of pitching-stone required and eventually obtained forthe training-works amounted to 28,300,000 cubic feet,the reserve being 15 per cent. of the quantity used. In the course of opening the quarries it was found that a large quantity of stone of good quality,but too amall forpitching-stone became available.

Experience gained in the working-season of 1900-~910of the difficulty of burning bricks of good quality and in sufficient quantity in the damp climate of Bengal, and the occurrence of small stone in the quarries, decided the question of the material to be used in the foundationsin favour of cementconcrete, which possessed the advantageover brickwork of nearlydouble the weight in water, a mostimportant attribute in sinking well-foundations to great depths. To this may be added the certain and continuous character of the supply of stone, and the cheapness at that time of cement and Xnglish freights as compared with the cost of Satna or Katni limewith a landcarriage of 773 miles. No hydrauliclime could beobtained in Bengal, and the limesmentioned set but slowly underwater. The decision to usecement concrete increased the quantity of stone to be carried by 4,500,000 cubic feet. The total quantityactually handled, including ballast for the approaches, amounted to 39,000,000 cubic feet, or about 1,857,000 tons. As there was at the time a shortage of rolling stock on Indian railways, 350 broad-gauge and 286 metre-gaugeballast-wagons wereobtained. The broad-gauge trains carried 800 tonsand the metre-gauge trains 400 tons. The railways charged Rs.6 per train- mile for broad-gauge and Rs.2 per train-miIe for metre-gauge for haulage and working. After the first month the trains were rnn strictlyto time-table, the railways giving them precedence Over ordinary goods-tmins. It may be mentioned that the total amount paid t,o the East Indian and Eastern Bengal Railways, for this and other construction traffic, amounted to about 27 lakhs of rupees, almost the whole of which thus returned to Government as profit onthe working of theirrailways. For the carriage of stone by water from Phudkipur, steamers and flats were chartered with the option of increasing or decreasing the number of steamers or flats employed as required by the circumstances of the work. The flats carried an average of 700-tons, and a steamer brought two flats and did the round trip in 3 days. All stone was paid for on weighings Over a weigh-bridge, converted to cubic feet at rates determined by experiment ; thatfor standard trap pitching-stonewas 21 cubic feet to the ton. Power.-On account of the magnibude and comparativelycon- centrated character of the work it was decided to employ electric power throughout in the construction of the bridge. Owing to the large first cost of a cable across the Ganges, and the certainty that it could never be recovered from the shifting sandof the river-bed, as well as the impossibility of repair in case of a fault, two power- houses were built, the larger at Bahirchur on the right bank, and

the smaller at Pakseyon the left bank. The bridge was built out from both banks, and as soon as aerial transmission could be obtained across the river the Paksey power-house was closed down, and the whole construction was worked from Bahirchur. The plant at Bahirchur consisted of three Babcock-Wilcox water-tube boilers, withtwo 325-kilowatt Belliss-Westinghouse triplesets and one 125-kilowattBelliss-Westinghouse compound set,and that at Paksey of three Babcock-Wilcox water-tube boilers, with one 325-kilowatt Belliss-Westinghouse triple set, and two 125-kilowatt andone 50-kilowatt Belliss-Westinghouse compoundsets. The current was generated at 440 volts, 50 periods, three-phaseand was transformed up to 3,300 volts for the bridge circuits. It was transformeddown to 440 voltsfor supply to the machines. On completion of the bridge the whole of the plant was transferred to the Eastern Bengal Railway for the electrificationof the locomotive and carriage and wagon shops, and the cost of power was found to have been3 annasper unit. Some troublehad been anticipated owing to the dampness of the Bengal climate, andall the electrical plant was insulated with mica and designed for a temperature-rise of55" F. above atmosphere in England after a run of 6 hours on full load. The plant worked throughout with great freedom from breakdowns or other troubles. Block-yavds.-Cement concretehaving beendecided on for the well foundations, it was evident that great certainty and rapidity of construction would be obtainedby casting the concrete into blocks of a size which could be handled by the machinery required for dredging, and that the crushing of stone and the manufacture of the blockswould provide a steadyload for the power-plant during the flood season, when actual work in the river was at a standstill. Twoblock-yards wera established, one at Bhairamara, fed with stone by rail from Pakur and with sand from Khanyan on the East Indian Railway, 105 miles from the bridge, and one at Paksey, fed with stone by river from Phudkipur and with sand from Siliguri at the foot of the Himalayas on the Eastern Bengal Railway, 196 miles from the bridge-site. Numerous experimental tests showed that these were thenearest availablesources of supply of a reliable sand, so deficient is Bengal in every kind of buildingmaterial. The sand from the river-bed was found to be useless owing to the presence of a large amount of mica, and the expectation that reliablesand would be obtained insinking the wells was not realized. The equipment of each block-yard was practically identical, and consisted of three 20-inchby 9-inchcrushers with elevators, one

batch mixer with an elevator and a 10-ton travelling gantry, with the necessary 2-foot track, tip-wagons, moulds, etc. The method of working was as follows : a tip-wagon received its charge of sand at thesand-bins and was thenrun under the crusher where it received its charge of ballast, thence through the end of the cement-shed where the cement was measured into it. The tip-wagon was thenrun to the mixer, where it tippedthe charge, consisting of 10 cubic feet of ballast, 5 cubic feet of sand, and 1- cubic foot of cement, into the elevator, which delivered it into the mixer. In the mixer a measured quantity of water was added to the charge, 9 to 10 gallons, depending on the humidity of theatmosphere, and after being mixed for 3 minutes, it was discharged intoanother tip-wagon, running on elevated tracks, by which it was takento the mould to be filled. The moulds were made of hardwood andstood on a concrete cement- plastered floor. To prevent the block from adhering to the floor, zinc sheets were placed under each mould. The sides of the moulds werewhitewashed forthe same purpose. The mouldsbeing of wood, it was necessary to check each mould with templates after setting up. Experimentswith mild-steelmoulds showed themto be preferable,though somewhat more expensive infirst cost. Very compact and uniform blocks were obtained by spading the concretethrough and through with narrow iron spades fixed on gas-pipe handles. After setting for 3 days the moulds were struck, and on the seventh day the block was removed and stacked by the gantry. Blockswere allowed to mature for a minimum period of 2 months beforeuse, and they were keptwet for 1 month.The concrete employed was mixed 1 :3: 6. The ballast passed through l2-inch screens, and crusher sand and $-inch ballast was screened out for use in the pier face-blocks to be described later. Holes for T-headed Iewis-boltswere cast in the blocks, and by this means they were lifted and afterwards set in the work without difficulty, The blocks weighed from 5 to 73 tons each. Each blockyard, using 200 moulds, cast in this manner 600 blocks a month. The gantry was designed so that by means of an opening in the frame andan extension of the overhead runway,the blocks could be loaded ontrucks on a sidingoutside of the moulding-floor. The span of the gantry was 53 feet and the speed of travel 200 feet per minute. The pier face-blocks were made at the Paksey block-yard and consisted of 1 : 2 : 4 concrete, the sand being crusher dust and theballast &-inch screenings.These blocks were made in cast- iron moulds and were handled to the stacking-ground and again into trucks by means of hand-worked lifting-blocks running on carriers on overhead bulb-iron runways. The face-blocks weighed 8 cwt.

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 33 GALES ON TILE IIIBDLNGE I1lUDGE [:Yinules of Wor7cs7~op.-The main workshop, comprisingsmithy, machine- shop, foundry and saw-mill, was located at Bahirchur. A smaller workshop was provided at Paksey. Lay-out o-f Seitlements.-The headquarters station was situated on the left bank of the river, about 1 mile above the bridge. Although it was below high-flood level theground was the highest in the neighbourhood, and the access by rail and river was the most con- venientavailable. Here ten brick bungalowswere constructed for officers, the footpaths between them being embanked to keep outflood-water; adjoining were the offices (steel-framedsheds with 10-inch brick walls), a European subordinates’ settlement of thatch-and-mat bungalows on brick plinthsraised above flood- level,a settlement of thatch-and-matquarters on raised plinths forIndian employees, a market of steel-framedsheds with corrugntediron roofs andmat walls, and a hospitaland dispensary, consisting of a double-storiedbrick buildingwith thatch-and-mat annexe. The ground, as is always the case in the delta, sloped away from the river towards low ground to the east, and advantage was taken of this to construct a storm-water drainage system, the spoil from which was employed in making the embankments an3 plinths. A marginal levee along the river-bank kept out the river flood-water. A piped water-supplyand electric lights and fans in the officers’ quarters werealso provided. Mat-and-thatchedquarters, though cheaperand quicker to build in the first instance than brick houses, were so expensive in maintenance that after the third year the brickquarters were found to be the more economical, apart fromthe danger of fireto which thethatched quarters proved extremely liable. A similar station of smaller extent was built on a recent char at Bahirchur on the right bank downstream of the approach bank andabout 1 mileback from‘the bridge. This was occupied as soon as it could be made accessible by a siding from Bhairamara with a pile bridge crossing the back channel. Previous to this the staff employed on the preliminary works were housed in quarters provided at Bhairamara. Wuter-SuppZy.-Having in view theliability of the district to outbreaks of cholera, the danger of fire to the thatched quarters, andthe supply requiredfor the power-house,block-yard and engine-shed, a comprehensive water-supply scheme was adopted at Paksey. Water was pumped from the river into a pair of settling- tanks,and thence after sedimentation into a pair of overhead.

Char = land thrown up in the bed of a river. (Imp. Gaa. of India.)

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] OVER THE LOWER GANGES AT SARA. 33 tanks, whence aportion wasled throughgravity sand-filters to the officers' andsubordinates' quarters and the hospital; the remainingsupply was deliveredby piping tothe power-house, engine-shed and workshops, and to standpipes for the rest of the quarters and coolie-lines. The scheme designed for 100,000 gallons aday supplied at onetime double this quantity. Each settling- tank had a workmg-capacity of 100,000 gallons a day, and consisted of a concrete floor 75 feet by 30 feet, surrounded by an earthen embankmentlined with clay puddleand dry brick. At oneend was an inlet chamber in which the coagulent, " alumino-ferric " in solution,was mixed with theriver-water. The quantity supplied varied from 14 grain per gallon to 3 grains per gallon, according tothe turbidity of thewater. The supply was regulated automatically by a needle-valve controlled by the depth of water running through a triangularnotch. The water cleared in about 8 hours, and after settlement was pumped into the overhead tanks. Each of the two tanks had a capacity of 30,000 gallons, and was mounted on a 50-foot staging. The filtering arrangement consisted of threesand filter-tanks, 8 feet by 8 feet by 4feet, and three storage-tanks,on &foot and 40-foot stagings respectively. TWO pairs of tanks were used at a time. Theunfiltered water from the pipeswas tested daily for the presence of: (a) excess alum,and (b) free acid. No test at any time showed the presence of either. The filtered water was tested weekly by the chief medical officer, and was always found to be of good quality. The hardness was about 8 parts per 100,000, almost all of which was permanent. At Bahirchur the water-supply was drawnfrom a well sunkinto the char, which must have been formed since 1868, the river having moved 2 miles across country fromBhairamara to its present site since that date. The water provedextremely hard, and it was foundnecessary to install a water-softeningplant for the power-house supply. Outside the range of the piped water-supplies all coolie-camps were furnished with tube-wells in charge of chowkidars, and the pure supply of water thus ensured was effective in keeping down sickness. The Training-Works.-By theend of therains of 1910 the collection of pitching-stone in depots at Bhairamara from Pakur, and on the river bank at Paksey from Phudkipur by river, and at the back of the left guide-bank from Jainti was well in hand. The conversion of the Cooch Bihar2-foot 6-inch line to metre gauge by theEastern BengalRailway had by thistime put the Jainti Qnarry intodirect communication with the bridge-site. It was obligatory to construct in the one season a continuous guide-bank [THE INST. C.E. VOL. CCV.] P

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 34 GALES ON THE IIARDINGE BRIDGE [Minutes of at least 30 feet wide on top and 5 feet above high-flood level for the whole lengthaf the approaches, and to protect the slopes with pitching-stone, inorder to obviate the possibility of theriver outflanking the bridge-site, although at the location selected there was little danger except on the right bank, whereold the Dhairamara channelstill formed a deepdepression. It was alsonecessary to constructenough of theguide-banks to secure the site. By Novemberwork had been fairly started when cholera broke out and stampededmany gangs of coolies. Bygreat exertions some were induced to remain, and the disease was stamped out and work proceeded. On the 1st January, 1911, the first train of stone was run down to the apron at the tail of the left guide-bank, delivery by river having been started somewhat earlier. By this time there hadbeen collected at the depots at Bhairamara 1,600,000 cubic feet of pitching-stone ; at Paksey, 2,100,000 cubic feet ; and behind the Left Guide-Bank, 1,300,000 cubic feet. The first train of stone was delivered at the Right Guide-Bank on the 1st February, 1911. Stone was now being delivered at the Right Guide-Bankby broad- gauge trains running direct from Pakur and by local trains from the depot, and at the Left Guide-Bank by the chartered steamers and flats directfrom Phudkipur, by bridgelaunches and flats from the riverside depot at Paksey, by metre-gauge trains direct fromJainti, and by local metre-gaugetrains from the depot. During March2,100,000 cubic feet were placed in position, In March work was againchecked, particularly on the Right Bank, by a second outbreak of cholera, and the completion of the ends of the guide-banks became impracticable. However, by raising the levels of the apron, work was continued as the river rose, and by the end of August a total of 10,800,000 cubic feet had been placed in position out of the 15,000,000 cubic feet required to complete the twoguide-banks. The obligatory portion of theearthwork of the approachbanks was alsocompleted and protected by stone pitching. No change occurring in the river during the ensuing floods, the pitching of theends of theguide-banks wascompleted inthe followingseason, 1911-1912. Inthis year also theconstruction of the Raita Bank was undertakenand wascompleted with the exception of 900 feet of theupper end, the site of which was occupied by a passenger ghat (landing-place) at which the Eastern BengalRailway were in that year working the passenger transhipment service. They also had B broad-gauge wagon transhipment ghat at thelower end. It is worthy of remark, as exemplifying the changeable nature of the river and the uncertainty of tLe position

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] OVER THE LOWER GANGES AT SARA. 35 of practicable ghats on the right bank of the river, that during the construction of the bridge the traffic had to be worked in successive years from Golbathan 9 miles below Sara, from Bahadurpur 3 miles above Sara, from Raita 6 milesabove Sara, and from Damukdia, exactlyopposite Sara, besides numerous minor changes during theannual rise and fall of the river,and even during the low- waterstage of theriver, when considerable changes occurredon more than oneoccasion. By the end of season 1911-1912 a total of 19,600,000 cubic feet of stone, inclusive of the previous season's work,had been placed in positionon thethree guide-banks and the approachbanks. In 1912-1913 RaitnBank was practically completed, and in 1914-1915, after the opening of the bridge to traffic, the Sara Bank was constructed,by which time a total of 24,600,000 cubic feet of pitching-stone had been placed in position, includingpitching of toes of approachbanks, pitching of minor flood-openings in approachbanks and pitching around piers, and 3,700,000cubic feethad beencollected a.t the reservedepots. In February, 1912, bythe Government census return, the labour andstaff employed inthe quarries and on the worksnumbered 24,400, a figure which may be takento be thelargest number employed at any time on the project. Sefting out.-After the position of the abutments had been fixed by triangulation, the positions of the piers were obtained by inter- . sectionsfrom subsidiary base-lines setout on the guide-banks. Thesebase-lines were used for settinganchors for moorings and for centeringthe sinking-sets; but for grounding caissons and settingout piers andall final workmeasurements were carried forward from each abutment by wire span measurers. These Were set on measured bases checked by invar tapes immediately before use. The invar tapes, which at air temperatures have a coefficient of expansion of 0~0000001,were checked at the National Physical Laboratory,Teddington. The mean temperature inEngland where thegirders were manufactured is 62" F.: the mean temperatsure of Bengal was taken to be 91" F. As the track was carriedfrom girder to girder on steel stringers and the whole length of the bridgewas thus steel throughout, it was necessary to make an allowance both for the difference in mean temperature between England and Bengal, and for the extension of the bottom booms under deadload, and the dimensionof 359 feet centre to centre of piers for which the girders were designed was increased to 359.1325 feet in setting out. The measurement between abutments as fixed by triangulation proved to be 3f',f inches short, an WIYX of 1 in 20,000, and it was found necessary toshorten the D2

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 36 GALES ON THE HARDINGE BHIDGE [Minute8 of closingstringers. It may be mentionedhere that girder-expansion was allowed for on the stringers over the piers, and that stringer-expansion was allowed for in the design of the girders at two points in the length of the span. In carrying the levels across the river, shots 3,200 feet in length were necessitated by the width of the river, and an error of 2 inches occurred. This was remedied by packingup the girders affected on the right bank with steel packers over the bearings. Design of Curbs, Wells and Piers (Figs. 11-13, Plate a).-The wells are rectangular in plan, with semi-circular ends, and measure 63 feet in length and 37 feet in breadth, with two dredging-holes 18 feet 6 inches in diameter, The curb is 15 feet 7 inches in height, and is built up of &-inch steel plates and angle-bars. The cutting edge consists of a 7-inch by38-inch by &-inch tee, the drum plates being attached to the back or table of thetee and the cant plates to the stalk. The cutting edge is further strengthened by two plates 3 feet by 3 inch and 12 inches by 1 inch respectively. The construction gives great lateralstrength to the cutting edge. The cant plates are carried upto an angle-bar ring which forms a shelf or bearingfor the falsebottoms used in groundingthe curbs in water. The curb forms the lower portion of a watertight caisson, which is carried up in strakes 7 feet high to the height required by the depth of water in which it is to be founded. The strakes are connected by lap joints to reduce riveting, the plates being set in and out like ship-plating. The strakes are designed of varying strength, suitable for founding in water up to a maximum depth of 50 feet. Above the curb when founded on a sandbank, or above the caisson when founded in water, a light inner lining of -&-inch steel plates, after- wardsdesignated upper trunks, is carriedup in rings 9 feetin height, giving vertical strength against earthquakestresses, provid- ing against bursting forces due to water rising inside in the case of heavy“blows,” and furnishing at the same time a form for the mass concrete of the centre wall and the concrete Wing between the concrete block masonry and the inner lining. The steel lining also prevents the escape of the sand filling should the steening for anyreason not be watertight.The curb or caisson, as the mse may be, is filled with concrete, and the steening is carried up from the top of the mass concrete in block masonry, built of the concrete blocks previously described. To prevent the ripping-up of the block masonry inrapid building and sinking, and to give additional vertical strength, eighteen vertical steel rods, 12 inch in diameter, are attached to the steelwork of the curb or caisson, and are carried

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. l’r(JceediW.1 OVEE THE LOWER GAiSGFR AT SBRA. 57 up to the top of the steening in 12-foot 4-inch lengths. Bond-rings of 6-inch by &inch steel bar are provided with each length of rod. The vertical rods lie in recesses cast in the sides of the concrete blocks (Rg.16). The concrete filled into theserecesses assists to bond

FEE

LAYOUTOF CONCRETEBLOCKS IN WELL-STEENIXG.

the whole together. The dredging holes of the first wells, Nos. 1, 2, . 15 and 16, aftersinking, were filled withsand to within 18 feet 6 inches of the top and plugged withconcrete. Subsequent wells were also plugged with 18 feet of cement concrete at the bottom for reasons to be described later. Vertical bond-rods were carried

up from the upper trunks to the topof the pier masonry and bond- rings were also provided in the pier. Owing to the great depth of the wells and the consequent heavy loadon thefoundations at the foot of the wells it wasconsidered , desirable tolighten the superstructure as much as possible, and the pieraccordingly consists of twoportions, a masonryplinth extending from the top of the well to high-flood level and a steel trestle weighing 140 tons above that point. This design facilitatutL the use of a service-girder in the erection of the main spans its described later.The masonry pier consists of a lower slab of reinforced concrete resting on the steening and concrete plug and bondingall together, a shaft of brickworkwith concrete-block facing, and a top slab of reinforced concrete. In plan the pier is 55 feet in length and 29 feet in breadth, with semi-circular ends. The construction, with trains on each track, gives a maximum load of 9 tons per square foot on the sand foundation at the foot of the well, allowing for displacement with the river at low-water level, but without allowance for skin-friction. No sinkage has occurred in any of the wells since their completion. Well-Building and Xnking Plant.-For sinking the well-foundn- tionsin water, four sets of sinking-plantwere employed,each consisting of a pair of steel pontoons 150 feet by 25 feet by 8 feet, strutted 42 feet 6 inches apart between rubbing-timbers, by means of transverse girders bolted to thedeck at bow and stern. Diagonal bracing of 6-inch hawsers with turn-buckles prevented independent movement fore and aft and enclosed a space into which the curb could be floated. An overhead steel staging bolted to the deck of the pontoonscarried two travelling electric cranes. By means of transverse and longitudinal travel the cranes were enabledto plumb any point in the dredging-holes and to discharge dredgings into the river or into bargeslying alongside the pontoons and to set the concrete blocks. The craneswere designed tolift 10 tons at a speed of 120 feet per minute for dredging, and to exert a pull of 15 tonsfor 10 seconds onthis gear. Electrical tests, however, showed that in dredging in Ganges sand there was no momentarily greaterforce required to break the dredger out of thesand after closing than wasrequired in lifting in water after leaving the bottom.The cranes had a secondspeed of 25 feetper minutefor setting blocks. Thelifting-speed of 120 feetper minute was found to be too fast for the brakes with the 100-cubic- foot dredgers, which, when full of sand, weighed 9 tons, and much of thedredging was done on the low speed. Thecranes were subsequently altered to a lifting-speed of 80 feet per minute. The

overhead staging was designed to stand on its outer legs for use onland. The staging also carriedon a lightelevated frame the strainingtops for the power-transmission line. Eachsinking-set carried three concrete-mixers. The concrete was for the most part handledfrom the mixer to the work by coolies ; butthe more satisfactory way was found to be to lead the concrete by a flexible pipe from an elevated mixer. Otheritems of plantwere eight 100-cubic-foot Bell dredgers. Two of these were converted during the progress of the work into automaticwire-rope worked dredgers, which were found to be a greatimprovement ‘on those worked by chain. The wire-rope worked dredgercan beworked by the crane-rope of anycrane without special pulleys and with a minimum length of jib, Five 8-inch vertical-spindle motor-driven centrifugal pumps were also obtained, provided with piping and appliances for sinking by suctiondredging. In the deepwells difficulty was experienced in controlling the suction-pipe, and as the direct dredging with the 100-cubic-foot grabs was certain and satisfactory, suction dredging was not proceeded withafter the first experiment. The pumps were satisfactorily employed in deepening channels and were regu- larly used for ‘‘ running ” the wells. The rapidity with which an electrically-driven centrifugal pump can be placed in a well, and the ease with which it can be worked, and lowered or raised to suit the water-level, make “ running ” a process fo: regular use in well-sinking instead of a last resort when dredging fails. The lowering of the water not only increases the weight of the well by a reduction of buoyancy, but appears to have a much greatereffect in loosening the frictionat grip of the sand by inducing a flow of water down the sides of the well and under the curb. For handlingthe concrete blocks and pther materials from the bank to the bridge there were three floating Scotch cranes lifting 10 tons at 80 feet radius, two small paddle-steamers, three steam-launches, eighteen 100-ton deck barges, eight 150-ton well barges, two pontoons 150 feet by 25 feet by 10 feet, besides smaller craft; and when in full work thefleet was taxed to its utmost capacity. Well-Sinking.-The bridge-site having been secured by the partial construction of the flanking guide-banks, bridge work was started in the early part of working-season 1911-1912 on the abutment wells Nos. 1 and 16. The curbs were pitched on benches left in the guide-banks at ground-level, so that the amount of sinking to be doneon these wells was about 180 feet.The overhead sinking- staging described was erected on piles ashore standing on the outer lags, which were thus 28 feet G inches fro;? the walla. The stagings

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 40 GALSS OB ?Hb HAkbIXGEF. BirIDCk )~8hnrllmut were cumbersome ta erect ashore, and there was danger from blows the wells began toget down toconsiderable depths. For this reason the wells were heavily weighted for the final length of sink- ingwith concrete blocks setdry. A surcharge of 3,224tons was thus placed on No. 1 well. Pumping was not at first employed, as it was feared that blows would be caused thereby, It was, however, eventually found necessary to resort to pumping, and it was then found, as should have been obvious from the beginning, that there was less danger of blows frompumping than from continuous dredgingwith little progress, Well No. 2, whichfell on ahigh char, was also sunk with a set of the overhead staging erected on piles. The depth of sinking through sand in this case was 185 feet, and this was accomplished with a surcharge of 3,858 tons of dry blocks. Well No. 3, also pitched on the cbar, was sunk by means of an electric derrick crane. By this time pumping was freely used, and dry blocks pointed were used only as a coffer-dam, to enable sinking $0 be continued after the rise of the river. All the remaining wells, whichwere pitched either on low char or inwater, were sunk withoutartificial loading with the greatest ease, Theheavy steening adopted in the design enabled the three wells, Nos. l, 2, and 16, to be sunk without much difficulty in one season, thereby carryingthrough the .programme ; whereasa lighter well would have entailed disastrous +lays at the very outset, The experience thus gained allowed the workto proceed with confidence on KO.15, the first well to be sunk in water,although, owing to various causes the caisson could only be pitched so late in the season as the 3rdMarch. Thecurbs weighed 144 tons,drew 9 feet of water when afloat, and contained 28,000 field rivets ; they consequently took a long time to erect. No. 15 curb was erectedon a pair of wooden pontoons clamped together by means of a timber grid on deck and crosstimbers below. Thepontoons were' fitted at one end*withpipes, through which water could be pumped into or out of the pontoons, and with air-escape pipes. After an unsuccessful attempton other lines the curb was launched as follows :-The pontoonsand curb were brought inside the sinking-set, and the pontoons were loaded with sand-bagsof a weight not quite sufficient to overcome the buoyancy of the woodwork of the pontoons, an initialdip of a couple of inchesbeing given tothe end of the pontoons away from the pumps. A 5-inch steel hawser was passed under the lower end of the pontoons, and with a given amount of slack made fast to the legs of the staging. Water was then pumped into the pontoons, which rapidly dipped until they took a bearing

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 1’1-oceediugs.-l OVER THg LOWEIL GANGBB AT SABA. 41 on the wire rope just before the top of the curb would have gone underwater. By continuing the pumping the pontoons became. entirely submerged, and the curb, floated level. The pontoons were then pulled out from under the curb by a steam-launch, and came slowlyto the surface, when the bags were thrown off andthe pontoons pumped out. As soon as the curb was afloat it was fitted with a false bot,tom, consisting of a central casting with radiating teak spokes butting on the casting at one end and on the ledge formed in the curb at the other. The spokes fitted closely together, and with a little caulking were easily rendered watertight. At No. 15 well, the water being 20 feet deep, two strakes were added, making a caisson 30 feet in height. The bed of the river at the site of the pier was covered with a single layer of sand-bags to prevent scour as the curb approached the bottom. The sinking-set was moored roughly in position by means of adjustable hawsers laid out diagonally, and the caisson was moored independently at the bottom and to the sinking-set at the top (Fig. 17, Plate 3). Owing to the weight of the caisson when partly filled with conwete, and to the fact that there was usually not much current at the time of founding, the independent caisson mooringwas, afterwards, usually dispensed with. Concreting wat; then carried on until the cutting edge was within about 6 inches of the sand-bags. The caisson was then carefully centered in correct position and thevalves in the false bottomswere opened, The caisson then dropped anamount proportionateto its draughtand bedded itselffirmly intothe bottom. It was necessaryto give the caisson a good grip as instantaneously as possible, on account of cyclones and of the north- westers which are of frequent occurrence during March, April and May.These storms often blow withcyclonic force for a few minutes and were the causeof many precautions and much anxiety. After a shortexperience 6-ton concrete blocks were used as anchors for the sinking-sets-and for all important work. Sinking on No. 15 was started on the 15th March and was com- pletedon the8th May, an average of buildingand sinking of 2.6 feetper day. The well wts builtduring the day and sunk duringthe night. Before sinking the last few feet, a temporary brick coffer-dam was built on the well to keep the water out of it while concreting the top plug, and to serve a as form for the bottom reinforced-concrete slab of the pier, which was thus built with ease below water-level.This safe andcertain method of startingthe pier, which was employed on the greater part of the wells, saved muchvaluable time. Well No. 15 is 159.58 feet belowlow-water level, and is believed to be the deepestbridge-foundation in the

world. It was of the, greatestimportance to found it this .season,because, as it is the nearest to the left guide-bank, there was every probability that in the next floods, scourwhich might extend to a depth of 100 feet of water, would occur there and make any subsequent operation difbcult. It also enabled girder erection on this side to be commenced in the following season. Meanwhile, in order that there might be no delay in starting foundations in the followingyear, arrangements for the erection of six curbs were put in harltl. The dificulty of finding any spot on the bank of the river where perlnarlellt contlitions obtained, was overcome by excavating a basin, or '' clock" ;M it cime to be called, at theupper end of theleft guide-bank, at right angles to the river.The spoil excavated was trainedinto the approach bank. The shore end of the dock, which was used as a harbour of refuge for a great part of the floating plant during the floods, provided U protectedslipway for launching-ways. Two curbs werebuilt here and were launched sideways onthree lines of ways. The fixed ways were built to a slope of 1 in 16 at the upper end and 1 in 8 at the lower end. The pressure between the moving and the fixed 'vays was 1 tonper square foot.Special tallow which did not readily melt in the sun was used. The first curb was launched as soon as the water rose in the dock sufficiently to float it. This curb stuck soon after entering the water, owing to a slight deposition of silt on the ways, and waspulled off by the paddle-steamer.The second launch was successful. For the purpose of the construction of launching-ways the Ganges at Sara was a river with one tide year, namely the monsoon floods. The dock silted at the mouth, and care had to be taken to get the curbs out as the river fell. Two curbs were built during the dryseason on the shelving char on theright bank, and werefloated as theriver rose. They were temporarily decked over to prevent them from being swamped, and were strongly moored; as the current on that side was slack, no trouble was experienced except on one occasion when the formation of a bigeddy tore out the stern moorings and threatened tobreak them adrift. They were however broughtunder control without damage. Two other curbs were built on wooden pontoons as described above. In the season 1912-13, as the river fell, curbs for wells Nos. 5 and 6 were grounded in position successively from the right bank on the char, which this year was of considerable extent, but the curbfor No. 4 wellwas erected on the char. No. 4 well was built and sunk by means of an 80-foot jib derrick,made out of two second-handsteel derricks. Two 15-ton h:md-wincheswere

convertedto electric hoists which derrickedthe jib and set the blocks. Thejib and pole were latershed by a &-ton electric hoist, working an endless rope in a channel-iron ring attached to the base of thederrick. The dredging was donewith 40-foot dredgers worked from a pair of wooden gallows which were placed in position on the well and removed entire hy the derrick. Progress was necessarily slower than with the sinking-sets, as the well had to be built and sunk in lengths, and building was never permittet1 at nightowing to the difficulty of supervision. No. 5 well WAS started by means of a floating electric derrick crane, and was there- afterbuilt and sunk with two 10-ton hand Scotch cranes;the centre pins were bored for the lifting-ropes, which were led down through the pin and under pulleys to a pair of 5-ton steam-hoists- the only steam-plant which was used on the bridge itself except the steam pile-drivers andlocomotives. No. 6 well was started by means of a sinking-set and was sunk towithin 20 feet of fulldepth when, owing toshoaling of the water, the sinking-set had to be withdrawn and the well completed with wooden gallows andthe electric hoists. Thesinking-set, which sank No. 6 in November and December, later in the season sank No. 11 well in Apriland Nay. The other three sets sank and completed wells Nos. 14,13 and 12, respectively. Thefor- mation of the char this year at the siteof the bridge prevented the nse of the sinking-sets to full advantage, for there is no reason to doubt that, with everything favourable, oneof these sets could have sunk three wells to the full dept.h in one season, and that each of thesets could havesunk two wells, includingconcreting of the caisson and filling of the well and base of thepier. When this point was reached the intention was to remove the sinking-set anti erect a 90-foot transmission-tower, furnished with two jib cranes to carry the transmission-line anti build the pier. The hollow left in the pier for the base of the tower was to have been filled with brick concrete after its removal. All arrangements and the design of the bridge, however, had to be modified by the coal- and other strikesin England, which, startingin March, 1912, delayed the supply of curbs, upper trunks, trestles and girders, andcaused great anxiety, although in the end no great delay. Concrete abutments faced with concrete blocks were substituted for the steel trestles, which, it was seen, could notarrive in time. There was little objection to the additional weight, owing to the great additional friction which could be depended on with these wells as compared withthose in the river. The upper trunks were dispensed with in wells Nos. 14 and 13, a crosswall of blocks being substituted

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 44 r:AtE5 ON THE HARDJBGE BRIDG~~; [JIinut,es of forthe massconcrete. A bottomconcrete plug which had been adopted in No. 3 well, owing to the upper trunks during pumping not having proved as watertight as was expected, was made standard for the rest of the piers. The sinking-sets remained to build the piers up to the top of the shaft, which was now built solid ; and a small base, which was concreted into the top slab and left there, wassubstituted for the original base of thetransmission-tower. This procedure simplified construction. Thetransmission-line of threewires was carriedacross the sinking-seband later acrossthe bridge as follows :-The three wires at each end of a span were dead-ended to a triangle. Adjacent triangles were connected by a steel-wire straining-ropewhich passed overa pulley on the straining-top of the sinking-set. The transmission-wires were connected by cables. This arrangement allowed of movement of thesinking-set due to waves, of centeringthe sinking-set,and byslacking away thestraining-ropes further allowed the sinking-set to bedropped downstream sufficiently to erect on the pier the tower to which the transmission-linewas to be transferred.After transfer to the tower, the trestle was erected and the transmission-line was transferred to a bracket attached to the upstream side. The bracket was sufficiently outrigged to allow of the erection of the girders, and was high enough to provide a headway of 40 feet at high flood at the centreof the span. During thisseason, 1912-1913, thetransmission-line was temporarily carried across the river from the sinking-setat No. 11 well to No. 6 well by means of three 90-foot transmission-towers on piled staging 700 feet apart, and the Paksey power-house was shut down until theend of the season. In theseason 1913-1914, theremaining four wells, NOS.7, 8, 9 and 10, were sunk to the full depth and completed. No. 7 well was sunk successively by means of a sinking- set, a floating Scotch crane, a,ndthe jib derrickas the water receded. Thecurb after beinggrounded by loadingwith dfy blocks was shifted by the cyclone of the31st October, 1913, and had to be refloated and recentered. Wells Nos. 8, 9 and 10 were sunk by the sinking-sets. A summary of the results of the three seasons’ well-sinking is as follows :-In the first season five wells, in the second seven, and in the third four wells had been sunk. Two of these had been sunk 160 feet, and the remainder 150 feet belowlow water.One had been sunk 185 feet and two 180 feet through sand. In all cases the sinking of each individual well was completed in one season, and except in the cases of Xos. 3 and 4 wells the piers also were built the same season. Anticipating the narrative, it may be mentioned here

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.) OVER THE LOWER GANGES AT SARA. 45 that No. 14 well was sunk and the service girder erected upon it in one season, and that No. 10 well was sunk and the pier, trestle and main span of girders erected upon it in one season, and that No. 9 wellwas sunk, the pier and trestle were erected, and the service girder was transferredto it, in oneseason. Therapidity and certainty withwhich the wells were sunk admittedof girder-erection being undertaken continuously from both banks during 1913-1914 ; any failure to sink a well to the full depth in oneseason would haveinterrupted the programme and entailed great delay in the completion of the bridge. The wells on completion, having regard to their depth, were all in good position, the greatest error ?t the top of the wells being in No. 6, which was 8 inches west, and inNo. 10 which was 11 inches north of true position. At the bottom of the wells, No. 2 was 25 inches west and No. 7 was 22 inches north of true position. The masonry and steel work in the wells averaged 16,000 tons per well. The total quantity of masonry in the wells and piers was 299,000 tons. Elevencurbs and cBissons had beenpitched in water.Five of these were 37 feet in depth and this was the deepest caisson used. The deepest watermet with was 27 feet. The maximum current at the time of grounding was about 12 mile per hour. The maximum speed of building and sinking obtained with the sinking-sets for a complete well was 3-25 feet per day, obtained on NOS.8,9 and 10 we%. Progress on No. 6 well was 3.4 feet per day for 126 feet of sinking, when the sinking-seth,ad to be removed. Except the bands of clay in Nos. 3 and 4 wells no obstacles of any kind were met with. Obsta,cles anticipated were trees, which are washeddown theriver with every flood. Pipaland banyan trees up to 32 feet in girth, and 85 feet in height were found at Paksey, and all trees between Sara and the bridge-site which had already fallen in or were likely to fall were cut up and removed. In %=eof meetingsuch obstacles a pneumaticdrill, capable of working under water at a depth of 165 feet, was provided, to drill holes for blowing them up with explosives. It was fortunately not required. Afterthe site of the bridgehad been located, it was found that just upstream the river wascrossed by a number of abandoned telegraph-cables, the sheath of the cables being a wire ropeabout 5 inches in circumference.These also were miracu- lously avoided, and the Selby chain- and wire-cutter provided for the purpose of cutting them was not used. All the wells were protected from scour by stone pitching, to the extent of about 100,000 cubic feet,except Nos. 3 and 4, which passed through claybands. For these 50,000 cubic feet wascon-

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 46 GALES ONTHE IIARDINGE BRIDGE [Minutes of sidered sufficient. Theouter ring of stonewas' enclosed in wire nets, and in some cases surplus concrete blocks were used. Nos. 11, 12 and 13wells were caught, unprotected, by a sudden rise of 73 feet in 4 days, and as the whole set of the river at this stage was con- centrated upon them,very rapid scouroccurred. Soundings of 90 feet being obtained downstream of the piers, stone was thrown in from pontoons moored by means of concrete blocks upstream of the piers, and thescour was brought under control. Prickings taken after thefloods showed that most of the stone had remained upstream of the piers andbare places werereplenished. Inthe case of piers round which the stone had been carefully placed, there were signs of the stone working downstream, and the stone upstream of No. 15 which was next to the apron, appeared to have been washed away and has been renewed. It was found that prickings in Ganges sand could be taken down to 80 feet below bed-level. Well-sinking b!l Pumping or '' Running."-Generally, running by pumping was resorted to when the wells would not go down with dredging a.nd weighting, for sinking through hard clay, and for the final founding of all wells ; in which case it was not necessary to excavate a sump below the final depth of the cutting edge, and the sand whichrose inthe curb remained as filling. The wells sank gradually and evenly during the pumping. The following figures for No. 4 well are typical :-

Depth of 1 Filling above Water 1 Period Cutting Edge~ Level , Cutting Edge helow Si,lkaye. pumped i of ~umpiug. 1 after Ground-Level.' down. 1 P'"lI)illg' l Pumpiug.

102 21 ~ 0 42 127 l9 0 55 145 166 19 0 55 166 19 1 0 42

During the running of a well, the quantity of sand rising into the sump and dredging-holes exceeds the displacement effected by the

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] OVER THE LOWER GANGES AT SARA. 47 well in sinking by 30 to 100 per cent., theaverage being about 50 per cent. Sinking-E$ovts.-Thc sinking-eEortsfound necessary in sinking wells Nos. 1, 2, 4 and 16, these being the wells on which the greatest depths of sinking from ground-level occurred, have been plotted on an extension of the diagram given in the Author's Paper on the CurzonBridge.' (F;r/. 28.) The. chartappears to show thatthe line of minimum sinking-effort is a curve and not a straight line, that is to say that thefrictional resistance to sinking does not vary directly with the depth but increases in a greater ratio. This might result from compression of the sand as the depth increases, causing a decrease in the angle of repose and an increase in the coefficient of friction between the sand and the surface of the well. In place of the straight dotted line in Fig.. 18 the full-line circular curve is therefore now suggestedas the curve of minimum desirable sinking- effort, in the design of wells for the sinking of which an efficient pumping-plant is available as an a,djunct to dredging.

SUPERSTRUCTURE.

Land Spans.--In the first design R 75-foot plate-girder span was provided at each end of the bridlge, to relieve the pressure of the bank and to allow of the passage under the line of the track on the guide-bank. In completing the face of the guide-bank at the left abutment a band of water-bearing silt, of a mean thickness of 4 feet, was exposed. It was found by borings to extend for 100 feet up and down stream, and for 250 feet under the approach bank. The band had an inclination of 1 in 18 towardsthe river. A similar isolated layer was found at the right abutment. As the heavy thrust of the 50-foot bank appeared to threaten the security of the abutment and of the guide-bank, any movement of which would be accompanied by slips in the approach bank itself, a viaduct of three spans of 75 feet at each end of the bridge was sub- stitutedfor the original design. Thealteration was carried out without delaying the programme, the bank being removed and the foundations put in during the floods of 1913. The piers are of concrete face-blocks with concrete backing, founded ona pair of 18-foot brick wells sunk 25 feet to 30 feet through the silt band. The shore ends of the 75-foot spans adjoining the approach bank are carried on reinforced-concrete piles, driven into the made bank and capped yith reinforced-concreteslab. The end of the 75-foot spanis

. ~ ~ --_.-

1 XlinLtes of ~roceet~ingsInst. c.E.,vol. clxxiv, p. I,

EINKrNG-EFFORT: CWT. PER SQ. FOOT OF WELL- SURFACE.

D = Sunk by dredging only. DP = ,,,, ,, and pumping. DW = ,, ,, ,, ,, weighting. DWP = ,, ,, ,, weighting and pumping. The numbers referto particular wells.

SINKINQ-EFFORTI)IAURA?d POR WELLS.

connected with the bank by a 12-foot span resting at one end on a bracket riveted to the 75-foot span, and at the other on a second (:onCrete slab on piles. The additional girders were erected at the latter end of 1914. Girder-Erection Plant.-The p1;:mt provided forgirder-erection consisted of 4,000 tons of timberfor staging for girders to be erected on the char, a steel servicle-girder of 336 feet 8 inches span for erection of girders in water spans (Fig. 19, Plate 3), two girder- erectiontravellers for erection from each end of the bridge, two sets of hydraulic riveting plant, steel travellers running on the top chords, and jib cranes for attachment to the posts of the girders for handling'the hydraulic riveting-machines, etc. As previously lnentioned, the portion of the pier above high-flood level consisted of a steeltrestle. The reduction in width of pier at thetrestle provided R step to carry the service-girder. The base of the trestle consisted of a pair of steel grillages, embedded in the concrete pier- cap, projecting nearly to the face of the masonry, and of sufficient strength to carry the service-girder and the main span erected upon it,together with all the necessary erecting-plant.Anchor-bolts, whicll engaged the legs of the trestles by means of steel castings, were provided to take temporary stresses during girder-erection, and t,hese and the trestle holding-down bolts were built into the pier; these were kept in position by templates during the process. The service-girderwas designed for a unit tensile stress of 12-tons persquare inch and for an 80-lb.wind-pressure per square foot of exposed surface. Thewind effect onthe main girder during erectionwas provided against by means of specialwind-frames attached to the top of the trestle. In view of the probability that span No. 15 would have to be erected partly over the guide-bank apronand partly over water which might be 100feet deep, the service-girder design admitteh of its use as a girder of any number of baPs sufficient to span the water portion, and of its being erected or dismantled afloat on pontoons by cantilevering. The connections of four bays at each end weremade by tapered bolts and of the three centre bays by rivets. The girder was 39 feet 6 inches deep over the chords, andwith this depth the bottom chordprojected 18 inches below high-flood level. During the floods when the girder could not be moved and was not in use, it was lifted on packings 8 feet clear of high-flood level by means of hydraulic jacks placed on tho top of the trestles, acting through suspension links attached to fire rocker-pins of tlle be;Lrings. The bearings were such that either end could befixed and the other free, according to the end fro111 which themain span was beingerected. The service-girderwas [,THE INST. C.E. VOL. ccv.] E

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 5 0 GALES ON THE HARDINGE BRIDGE [Minutes of alsoprovided with two pairs of steelwings (Figs. 19, Plate3), which could be attached to anyof the seven centrebays, to spread the weight on the pontoons while transferring from span to span. The weight of the span with traveller runways complete was 1,000 tons. The arrangements for floating the service-girder from span to span, Figs. 20 and 21, Plate 3, consisted of a pair of pontoons 150 feet by 35 feet by 10 feet each, divided into ten compartments by a central longitudinal and four transverse bulkheads. On the pontoons were erected fixed stagings 12 feet 6 inches high. The load was carried down the main posts to the intersectionsof the transverse bulkheads with the sides of the pontoons, and was distributed to the centre bulkhead' and intermediate points of the sides byinclined struts. The height of the fixed staging being 12 feet 6 inches, the highest water-level for moving the girder was 233.5. Thelowest water-level at which thegirder might have to be moved was 219. To provide for this difference of 14 feet 6 inches, and for intermediate water-levels, the further height required was obtained by building up an adjustable staging after the fashion of asleeper stack. To saveweight the sleeperswere made up of 14-inch by 4-inch pine planks with packings spiked to them at the bearing points. For the higher stacks, layers of 12-inch by 12-inch timberswere used at intervals,and the stacks and fixed staging werebraced to the pontoons with diagonal chains longitudinally and transversely. For letting water into the pontoons a sea-cock, worked from the deck, was provided in each compartment. For pumping water out, one of the 8-inchcentrifugal pumps was fixed on deckwith a separate suction pipe leading along the deck and down through a manholeto the bottom of each compartment(Figs. 21, Plate 3). Below the foot-valves theend of the pipewas wrapped inwire gauze, and was kept from coming too close to the bottom by three projecting set-screws. Immediately below the pump was a cast-iron chamber into which all the pipes led. With this arrangement every part of the pumping-apparatus could be inspected, and it was found possible, after starting the pump with all valves fully open, to regu- latethe pumping from each compartment, and the pump would continue working with all but one of the pipes shut down. Each poutoon wits fitt!e(l with five capstans for working ~~nwpo~us. The girdev-erectiontxavellers (Figs. 19, Plni3e 3) ::t,vndd!ed the girder to be erected with a apan of 41 feet 3 inches, and ran onateel runways carried on the timber staging or on brackets attached to the top boom of the service girder. They were 71 feet B inches in height, overall, with a wheel-bass of 41 feet 6 inches.This being

greater than the width of the top of the trestle, the rear endof the base was supported on a platform suspended from the main girder at the end of each season’s work, or, in the case of erection on the service-girder, whenever the service-girder was moved. The traveller was provided with four ’I$-ton electric hoists, able to lift two chord- sections simultar~eonsl. :It a speed of 30 feetper minute. The hoistswere traversed i ’ -Id. The travder speed was 10 feet per minutefor use ;tga.inst ?r 30 feetper minute under ordinar.. conditions. Girders.-The mainspans (Figs. 8 and 9, Plate 2) are simple girders of the modified Petit type 345 feet 14 inch from centre to’ centre of bearings. They are 52 feet deep and weigh 1,250 tons per span. They are designed under Government of India rules to the following scale of loading : chordmembers, standard B + 33 per cent., webmembers, standard :B + 40 per cent., floor members, standard B + 50 percent. This is equivalent in respect of the main girders to a train of vehicle,s weighing 1 S ton per foot, hauled by two eight-coupled locomotives with 20 ton axle-loads at each pair of the coupled wheels, and in respect of the floor system to an eight-coupledlocomotive with 23 ton axle-loads at each pair of the coupled wheels. Arrangementshad been made ,forthe supply of threespans of main girders and the service-girder in time for erection in the season 1912-1913. Owing tothe strikes only one main span and the service-girder arrived in time, and it was onlyby great exertionsand at considerable riskthat they wereerected before the floods. As the fears of a deepening of thechannel in span No. 15, onthe left bank, in ,t,he floods of 1912 hadnot been realized, a timber staging was erected in that span, partly on the undisturbed portion of the apron and partly on piles in about 25 feet of water. The girder-erecting traveller arrived in March, and was erected onthe approach bankand run out over temporary trestlesto the abutment. The main spanarrived in May, it was sorted on special grids laid down for the girder-yard, and erection of theportion first received wat; started on 12th May, 1913. To facilitate erection all gussetswere attached to the main members in the girder-yard. The normal date for the first considerable rise of the river is the 10th ,June. The girder came out in four ships, and owing to the congested state of the Port. of Calcutt,a and of the Eastern Bengal Railway an officer was deputed to Calcutta to super- vise t.he unloading and transport; arrangements. By the 20th &lay the hpau llnd Lbeen receiycd ant1 verified. Erect’iorl WVR:, then nus;!& on. It had heen forebeen that A qmn might have to E2

be erectedagainst time, and :L complete set of c:ylindric:d clrifts withtapered ends had beenprovided to fill 40 percent. of the rivet-holes. As there were 60,000 field rivetsin a span, it w:ts tlecided not to attempt any riveting but tofill the holes with 40 per. cent. of drifts a,nd 60 percent. of service-bolts, thedrifts being sufficient to carry the dead load of the girder.The rivet-holes to be filled with drifts were marked in the girder-yard with pa,int, and :t number denoting the lengthof drift tobe used was added. As soon as the girder hadbeen erectedand lowered to built camber, gangs were put on to fill the holes. Verystrict supervisionwas required to enbure, after two or three drifts had been driven to bring the steelwork into place, that all theservice-bolts were made tight before the remainingdrifts were driven. If thedrifts weredriven first it was impossible to bolt up close afterwards. The girder was struck on the 17th June, and was found to retain a residualcamber of 1.2 inch or t inch more than was calculated for rivets. The girder wasafterwards riveted at leisureduring the floods, andlittle difficultywas experienced in removing thedrifts. In thisand other spans erected in the same way, there were about 200 drifts per span which could not be driven out, and these mere removed by drilling. The river this year rose on the 15th June, and submerged the piles of the staging on the 18th June. The danger of the piles being washed out before thegirder wassafe was minimized by putting a layer of ,pitching-stone round them. Meanwhile a staging had been piled between piers Nos. 14 and 15 for theerection of the service-girder. Thegirder was erected bymeans of the floatingScotch cranes, one of which was fitted with a 105-foot jib to enable it to set the top booms. Erection of the service-girder was begun on the 12th May. The last pieces of girder workwere received at site on the 29th May, after having been lost forseveral days on theEastern Eengal Railway.The Rpm was struckon the 14th June, with the three centre bays fully riveted. The staging was rapidly dismantled, and by sawing tlrroughthe pilebracings the pileswere alleither drawn after beingsubmerged, OK*washed out during the floods and picked up below. Thetrestle on No. 14 was erected andthe service-girder lifted c1e;t.r of floods by the middle of August, and was lowered again after the floods by the end of September. In t,heseason 191:3-1914 erection of mtin sptn KO.1.4 011 the wrvice-girder was started on the 16th ( ktober, and the girder wa.s stmtck, tbree-qu~+~~.sriveted ant1 one-quarter drifted, on the, Xttl Ikxember.Erection on theservicesirder required some carc. Eachtime the service-girderwas moved the rocker-bearingwas

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceectings.1 OVER THE LOWER GANGES AT BARA. 53 setfor temperature, so that noundue inclination might result underchange of temperaturewhen it wasloaded withthe main span. Two scales were fixed to the bearing, one for use when the girder was lowered by the links, and the other when lowered by the pontoons.This wasnecessary, as the camber andlength of the girder between the bearingsdiffered according to the methodby which it waspln.ced in position.The service-girder had a built canher of 5h inches, and on first striking retained under it:; own weight'a camber of 29 inches. 'J'his was reduced after the erection of the firstmain span upon it by a permanentset of 4 inch to 2$ inches. When loaded with a mainspan and erection-plant it h1:L sag of l$ inch. The deflection under own weight, plus slack, m:ts therefore 3$ inches, and the further deflection under a main span and erection plant was 3h inches. The girders were erected on 20-ton screw camber jacks, four to each panel and subpanel point. A camber of 10 inches was set out on the jacks. This allowed for 43 inches, the built camber of the main span, 3& inches the calculated deflection of the service-girder, and 12 inch extra to allow for errors in calculation and faults of construction, and in order to make sure that the top boom closers would enterwithout difficulty, and that no jacking up from the service-girder wouldbe required. The results exactlyagreed with the calculations. After erection the girder, which was still flexible, was lowered to built camber, and all joints were made and either drifted and bolted or riveted.The estimated camber of the main spms after striking wa,s 1; inch. It was evident that the service-girder, in deflecting during the erection of the 'main span, would drag the girder work forward on the bearing, but it could not be foretold to what extent the main span would recover its position on striking. In erecting the first girder, No. 14, the fixed bearings were placed in correct position and the bolts connecting the girder with the top ansting were omitted. The girder moved forward +g inch and came back nothing on striking. It wasnfterw:wds pushed back into position by using one of the wind-frames to fix the rocker end, and allowing the girder to expand under increaseof temperature towards the fixed end whichwas lifted from timeto time to release the friction.All other spans wereerected inch back of their true position and the holes were caught when they became fair., Erection was arrangedto load the service-girder as evenly as possible. The bottom booms and floor system including the wind- bracing were first erectedfrom end to endand temporary wind frames were put in. These were steel angle-bar frames, attached to the end and next cross girder, which engaged in a box bolted to the

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 54 GALES ON THE HARDINGE BRIDGE ["ilut,es of top of thetrestle. The frames conld movt! lollgitudinallp but not transversely, andthey transmitted transvel3se wind-pressurefrom the main girder down to the trestle while allowing of temperature expansion. At the same time frames for longitudinal mind-pressurn werebolted tothe top of thetrestle and connected withthe fixed end of themain sptn by R pinand friction link. The frictiongrip was bolted up whenwind was expected, or when it was required to control any longitudinal movement of the girder. Next the lower halves of the posts and ties, and the lower member of the sway-bracing were erected, then the endposts and port'als, then the top parts of the posts and ties, and finally the top booms from each end towards the centre and the top wind-bracing and sway-bracing. Thegreatest care was requiredin striking the girder to avoid dangerous loads on particular points of the service- girder. Striking waseffected as follows :-a gang of nlcn starting from the fixed end lowered the jacks at each point of support SUC- cessively by an amount proportionate to a lowering of L- inch at the centre. As soon as the first gang reached the centre, a second gang startedfrom the fixed end and followed through, ancl this w:1s repeated until the girder was free. At about ldf way between the gangs a couple of men went through the jacks screwing up slack jackswith a shortspanner. The proportionate amount eachjack wa,s to be turned was marked off in paint on the thread from:I. fixet1 mark on the base of the jack. The, mark on the thread wns rubhetl off after each operation of the jacks and was re-marked for the next gang after the jacks had been tightened. In this way there was no cumulativeerror, and each set of jackscarried an spproxilnately equal load all the time. This was proved in practice by none of the jacks being found to be undnly tight or hard to turn. To move the service-girderto thenext span the wingswere attached at the third bay from the end. The two pontoons, with the adjustable staging built up according to the river level, were sunk by water-ballast to the required depth and brought under the wings, andthe staging was ptcked up. Thequantity of water taken in allowed for the compression of the staging, for the weight of the service-girder andstaging, for lifting the service-girder 6 inches, andfor the 6 inches of water in thebottom of the pontoonswhich could not be pumpedout. Each pontoon \vas centred and braced to the service-girder by means of four wire-rope tackles attached to the bow and stern and to four points of the girder.These tackles, which were tightened as the staging compressed, prevented any tendency of the warping-ropes to drag the pontoon out fromunder the girder in warping across. Each

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] OVER THE LOWER GANGES AT SARA. 55 pontoon was mooretl by SB-inch c?xtra flexible mire ropes to concrete block anchorsahead and astern and to the adjacent pier. Ropes were also led from eachpontoon to the corresponding piers and to correspontling astern moorings inthe next span (Figs. 21, Plate 3). The water was then pumped out, and on the girder being lifted clear of the pier the ahead rope; were slacked away and the stern Copes hauled in until the pontoons were downstream of the piers, when the pier ropes of the next span were hauled in and the girder was thus warped across. The 1e:ding pontoon was dropped a little further downstream than th,. other, and the inclirmtion thus girell helped thegirder across thecurrent. Ahead mooringsprevionsly laid inthe next span and buoyed onsmall pontoons were then picked up. Thefirst ahead moorings andthe first set of pier moorings were dropped, andthe girder was then pulled ahead intothe next span. With a lightdownstream wind the ope1-n- tion was easy, butwith a stl,ong wind upstream considerable stresseswere sometimes broughton the moorings andbracing- tackles. In dropping clownstrea,m from between the trestles and in rntering between the trestles in the new position, the girder was steadied by means of subsidiary tackles attached to the girders and trestles;and before landing,the girder was exactly centered by means of crossed chains with union screws, attached to the ends of the span and to the legs of thme trestles.The girder. was always under complete control, and the whole operation from starting the pumps to lowering in the next span took about 6 hours; of this 3 hours were occupied in punzping out, 2 hours in warping across, and 2 hours in adjusting therocker bearing and lowering. In theworking-season of 1913-1914 six main spans were erected on the service-girder, and the girder was moved forward ready for an early start after the floods ; and on the right bank five spans were erected on timber staging on the sandbank. For this purpose three sets of timber staging were employed. Piles were used under the staging fora portion of' the first span where therewas a deposit of silt, and in the fifth span where there was danger of the river rising before thegirder could 'be struck.Although the piling in No. 1 span had been completed the previons season, girder-erection could not be startedon this bank beforethe 22ndDecember, which may be compmed withthe 16th October, on which date erection on the service-girder had been started on span No. 14, and with the 6th October, on which span No. 8 was started on the service-girder in the following season. Thetimber staging consisted of H bentunder each panel and

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. 56 GALES ON THE HARDINGE BRIDGE [Minutes of subpanel point,with continuous longitudinal runners butted against the piers andtrestles and diagonalbracing. A steel runway similar to that used on the service-girder carried the traveller. The timber used mas Douglas fir imported from America, and no difficultywas experienced inobtaining the 14-inch by 14-inch balks in lengths of 50 feet required for the verticals of the bents. The staging from No. 1 and No. 2 spans was brought forward to No. 4 anrl No. 5spans in sections of threebents with bracings complete. The sections were lifted a couple of feet and placed on trolleys a.nd run out at right-angles to the bridge; the lifting of the section allowed longitudinal runners to pass, although joints were irregular in position. As soon :is the section was clear of t,he piers the trolleys were turned through a right-angle and the section XLS brought forward on a track prepared and levelled on the smd. On ;trriving opposite the second position the trolleys were again tmnerl and the sectionwas run into place. Thissystem effectrd a great saving in time B,S comp:tred with dismantling and re-erecting. At the endof the season all main spans received had been erected, those erected on the service-girder had arrived from England with thegreatest regularity by fastliners in time to avoiddelay. In the season 1914-1915 theremaining three spans wereerected 011 the service-girder, starting on the 6th October, :md the bridge was opened for goods-trafic on one track on the 1st January, 1915. T’he last sp:r.ns were shipped from Liverpool in preference to Ihst Coast ports,2nd snccessfrdly ranthe gauntlet of the enemycruiser

‘’ Emden ” in the IndianSeas. Two of thc! land spans were captured in Luxemburg, ant1 one was interned at Port Saidand hxd to 1)e replaced. The liner with half the last main span on bo:rrd w:ts com- mandeered in Calcutta by Government, and was only unloaded by special fa.vour. Of the fifteen spans five were struck fully riveted, two wllolly on drifts and the remainder riveted and driftedin v:mious proportions. No difference in camber or in behaviour under the Government test between those struck on rivets and those struck 011 drifts c0111d I)e detected. All rivets which could be reached by gap macliines were riveted by hydraulic power with a closing pressure of 25 tons. An instdlation of pumps and accumulator was situated at each end of tjhe bridge. The ram of the accumulator was 7 inches in diameter by 10 feet stroke, and the working-pressurewas 1,500 lbs. per square inch.Each pump, driven by a 24-HP.motor, wascapable of tleliveriug 150 cubic feet of water per hour against this pressure. Theremaining rivets were driven by pneumaticplant, of which there were six units. The standard unit consisted of a compressor,

with a capacity of 300 cubic feet of free air per minute, compressed to 110 Ibs. per square inch, driven by, a 7'0-HP. motor. The units mounted on pontoonswere easilymoved from pier to pier as required. The most rapidly erected girder was No. 7, which was struck one- third riveted in 9 days, and was fully riveted in 40 days from the commencement of erection. On an average tt span occupied a fort- night in erection and striking, and two months in riveting from the time of starting itserection. The service-girder was dismantled afloat in the following manner. The water in No. 6 span having shoaled, an 8-inch suction dredging- pump was used to deepen it. The pump was suspended from a small pair of shears over the bow of a 100-ton barge by means of a wire- rope tackle led to an electric hoi-st. By means of another electric hoist the bargecould bemoved aheador astern. The pump was successively lowered, raised and moved along the line to be dredged, ant1 in this way dug a succession of deep craters. Alteration of the mooring-ropesenabled an area to becovered. Thedredging was veryrapidly done by this method, and the compactness of the apparatusadmitted of dredgingunder the service-girder where head-room was insufficient for grab dredging. Meanwhile the wings of the service-girder were removed to the fourth bay from the end, and the pontoons being inserted at the fourth bay, the girder was lifted and brought out downstream of No. G pier,where it was moored across the scour-hole. The thee bays at each end of the girder were then dismantled by the floating derrickcranes, leaving five bays. A pair of thesinking-set pontoons, connected transversely by two spans of 60-foot plate girders, carrying a timber stack, was loaded up with 284 tons of sand in bags, and was brought under the centre of the girder and packed up. The sand-bagswere thentransferred to the service-girder pontoons and stacked along the outer strip of deck. This brought theouter bearing nearly free of the girder.Water was then let into the service-girder pontoons until the bearing was quite free, and the fourth bay at each end was then dismantled. The service- girderpontoons were then disengagedby the addition of more water, leaving a length of three bays on the central pair of pontoons where there was no difficulty in dismantling it. It may be mentioned that, exclusive of masonry reinforcement, the total weight of steelwork in the curbs,caissons, trestlesand girders of the completed bridge was 27,500 tons, requiring a total of 1,700,000 field rivets, of which all those in the curbs, caissons and trestles, ancl the less important of those in the girders, were closed by pneumatic plant. The important rivets in the girders, to

theextent of about 30,000 rivets per spm, >yew closed inthe hydraulic machines. Track over flke Bridge.-The track consists of BritishStand:%rd flat-footed 90-lb. rails on bearing-plates laid on teak cross sleepers. The sleepers are bolted to the bridge stringers. Each track is provided with inner guard-rails and outer guard-timbers. The bearing- plates are of two kinds,ordinary bearing-plates and creep-plates. The former are fastened to the sleeperby square dog sgikes, the head of which also holds the rail to gauge. These offer no resistance to creepor expansion movements. Thecreep-plates are provided with lugs between which the rail is finnly held by a steel key. The friction is sufficient to prevent longitudinal movement of the rail. The plate is independently fastened to the sleeper by screw spikes. Rail-creep is prevented from extending on to the bridge by laying the rails for ten rail-lengths at each end of the bridge on creep- plates. The girders were erected from both sides of the river with a fixed and rocker bearing on each pier, except where the girder- erection met, where there are two rocker bearings on the one pier,. At this pier, where temperature movements due to a length of 718 feet occur, railexpansion-joints are provided. At allother spans the rails are secured to the girders at the centreof the span by lay- ingtwo rail-lengths with creep-plates. All other rails are laid on ordinary bearing-plates and with the usual allowance for expansion. The rails move freely under the heads of the square dog spikes as required by the temperature movementsof the girders, and no expansion troubles of any kind have been experienced. Approac71rs.-The length of the line included in the project is 14.21 miles. It is builtthroughout for double track,but single track only has been laid from Ishurdi onwards. The main features are the approachbanks, which are 50 feet in height at the abutments of the bridge and contain 180,000,000cubic feet of earthwork, :L station at Paksey at the north end of the bridge on a 50-foot bank, and a large junction stationat Ishurdi for the Sara-Sirajganj branch. The gradient rises to the bridge from both sides, that on the north side against the load being 1 in 500, and that on the south 1 in 400.

The bridge, which as already stated was opened for goods-traffic single-lineworking on the 1st January, 1915, i.e., 3 yearsand 5 months from the commencement of the erection of the first well- curb, was formally opened for double-li’ne working and all classes of traffic on the 4th March, 1915. The working-season was for the most part from the 15thOctober to the 15th June. Medical Arrangements and #anitation.---At thebeginning of the

operations a medical and sanitary division was orgznized, under a Chief Medid Ofiicer. Theprincipal dangers to be fearedwere cholera and malaria,. Afterthe experience of thetwo cholera epidemics in the firstseason, it was realized that cholera wits endemic in Bengal, and, with the assistance of the Local Govern- ments, the jurisdiction of the Chief Medical Officerwa.s extended to :L belt of country surrounding the bridge works. By this means :my outbreak in the surroundingvillages was brought under control, and infection of thelabour atthe bridgewas prevented. The cholera isolation hospital WH.S brought in from an outlying situation :m

ramps, I and working-areas mere freely furnished with latrines, the objections of the na.tives of Indiato their.use are ineradicable, itnd the works were maintained in a sanitary condition loy p:ttrols of sweepers.

ORGANIZATIONAND CosT OF TEE WORK. The work was divided into seven main executive charges, termed divisions, as follows :-Quarries, comprising t,he supplyat the bridge site of stone and sa,nd ; Left Bank, construction of the bridge from the left bank and the approaches, with charge of the main settlement ; Bight Bank, construction of the bridge from the right bank and the a.ppro;xhes ; Power, supply of power and charge of machinery, workshops and fleet ; Stores, receipt and distribution of materials from England and country stores ; Medical, and Audit. r,llte engineeringdivisions were each in charge of an executive engineer, and were further divided into subdivisions in charge of nssista.nt engineers. The Caissons, trestles, and girders, aud the greater part of the plant, were constructed in England to the designs of the consulting engineers, Sir Alexa.nder Rendel, K.C.I.E., a.nd the late Mr. F. E. Robertson, C.I.E., to whose professional skill the bridge owes much, and to whom the Author is deeply indebted for much kindly help.

111 India the whole of the work \vas carried out by dep~rtlnentn.1 labour and petty contr:xt. Dep”trtment;tl labour was employed 0x1 thePower division, andto some extent 011 theRight and Left Bank divisions, but wherever possible work ~:tsclone by pet!ty contract. Cost.-The magnitude of the work, the high and inmensingcost of Indianlabour in the district, and the importance of rapid progress, were the determining factors in it greater use of modern plant and special methods of construction than had hitherto been considered economical inIndia. Nevertheless, very large hbow forces were employed on the training-works and appro:tchea, :~n(1 even on the bridge. At the commencement of operations wages at Sara were high, owing to the high rates that had necessarily been paid for goods transhipment in the jute rushes, and to the bad reputation of the place for cholera. The execution of any large work has a tendency to raise wages, and this is accentuated in bridge works such as the Hardinge Bridge, where the preliminary training-works have to be constructed inthe first working-season, andwhere in fnct each season’s workmust be carriedto a safestage before theannual floods. Thepay at Sara of unskilled labour, for example,was nearly clouble that in the Sonthal Pergunnahs, at the Paknr and Phudlripurquarries. The construction of the essentialtraining- works coincided with a greatdemand for labour for the Delhi Ilurharworks, and throughout the construction of the bridge there were times of scarcity sufficientlysevere to necessitate a famine allowance to the lower’ grades of Government employees. The establishment of markets at Pak’sey and Bnhirchur and strict supervision of weekly price-lists of food-commodities,however, prevented my great increase in labour-rates. Appendixes I to I11 show respectively the pay of varions classes of labour, examples of petty-contract mtes, cost of items of work, and the cost of the bridge and approaches. By dividing the cost of preliminary expenses,service works, plantand general charges between the cost of mainspans, land spans and training-works proportionately tothe net cost of each, which isapproximately as 64.5 : 1.9 : 33.6, the cost of thebridge may be shown :M follows :- Kllpcen. Main spans ...... 180,54,796 La11tl sl’au” ...... 5,13,849 “mining-works ...... 94,08,346 279,76,991

The cost of the main spns, divided by the :mea enclosed between horizontal- lines drawn through the base of the wells and the toPS of the girders and vertical lines through the centres of the abutments, gives a cost of Rs. 12 - 24 per square foot. For comparison it may be mentioned that the cost of the main spansof the Dufferin bridge, which is built with double-line piers and single-line girders, was Rs.9.71 per square foot. The cost of the well foundations, including steening, sinking and filling, was Rs.79 per 100 cubic feet of volume. The cost at the Chenabbridge at SherShah was Rs.69per 100 cubicfeet of volume for wells sunk to a depth of 75 feet, at the Kistna bridge Rs.68for wells sunkto a depth of 82feet, and at the Curxon bridgeover 'the GangesRs.66.5 for wells sunkto a depth of 100 feet.The cost of maingirders erected in place, including depreciation on plantand all charges, was Rs.370 perton. The corresponding ratefor the Dufferin bridge girders erected about 30 years ago appears to be Rs.408 per ton. Theextent to which the use of electrically-drivenplant has proved economical or otherwise is not susceptible of direct proof. A useful indication can however be obtained by comparison of the cost of working the Bhairamara block-yard, which at thebeginning was entirelysteam-driven, and the Paksey block-yardwhich WRS electrically driven throughout ; also of the cost of sinking NO. 5 well, which was done by steam plant, and of No. 4 well sunk in a similarposition by electricalplant. The comparison shows that the averagesaving by the use of electricityon stone-crushing, concrete-mixing,handling concrete blocks and well-sinkingwas Rs.0.307 perunit. On the whole project 3,096,695 units were generated, anddeducting 7;) percent. for transmission-losses, thereremains a balance of 2,864,549 units of power taken by the machines. Thistherefore would appear to show a saving of Rs.8,79,417 due to the use of electricity. The rate of 3 annas per unit, at which power was finally charged, covers depreciation of the generating,sub-station and transmission-line plant, the whole capital cost of the power-houses, sub-stationsand staff-quarters, and all erection, working and maintenance charges. There is no doubt that electrically-driven plant has on this work shown great superiority over steam in facility and convenience of vorking, and has contributed lxrgely to rapidity of construction. The nlachiues arelighter, mort, portable, and moreeasily put to work, the aclvantage being vc:ry great in such items as concrete- mixers, pumps and other apparatus which are moved from well to well as required. As the machines are lighter, stagings, gantriesand

travellers to carry them are also lighter and consequently cheaper. The difficulty of supplying coal to numerous isolated steam plants isobviated and a savingin rolling stock and marine plant is effected. For the running of workshops and other fixed machinery and for lighting, the advantages of electricity need no demonstra- tion. It may be mentioned that it wasnecessary to train on the work the machinery-inspectors,winders, crane-drivers, wiremen and all electrical staff, no trained Indian staff being available.

The Paper is accompanied by thirteen sheets of tracings, from which Plates 1-3 and the Figures in the text have been prepared, and by the following five Appendixes.

XPPENDIXNS.

APPENDIX I.

MAXIMUM AND hf1iYIMUhi PAY OF VARIOUSCLASSES OF INDIAN \vORKnlEK IN Rowss PER MONTH.

Class. ~ Class. Mal. Nin.

Min. ~ ~ ~~~ Max. I-_-- -~~ .- ~~~ ~ , Machinery-inspector . 70 (-~-55 I Erecting ssrang . . . 1 62 1 39 l Shift-engineer . . . 50 35 Bombay khallaks . . 42 1 34

Winder . . . . . , Khallasis. . . . . 24 12 40 ~ 35 1 Crane-drivers . . . 40 1 30 ~1 Steamer Sararig . . . 55 1 35 Pump-driver . . . 25 1 'L0 I Driver . . , . . 55 35 ~l Switchboard-attendant . 35 I 20 ;Il Khallasis . . . 13 12 Cleaner . . . . . Mason . . . . . 35 30 Wireman. . . . . Carpenter . . . . 50 20 1 'i Engine-driver . . . 60 I 35 1' Fitter . . ... 55 22 :; Fireman . . . . , 25 ~ 13 '1 Blacksmith . ... 50 20 18 Guard . . . . . 50 I 35 11 Hammerman ... 23 l1 Telegraph signaller. . Moulder . . ... 62 42 30 1 25

Timekeeper ~ Pattern-maker 70 40 . . . . 40 ~ 25 ...

Pointaman . . . . 10 ~ 9 ~ Boiler-maker ... 50 31 Permanent-waymate . ... 10 B Gangman ...... 15 9

Trolley-man . . . 12 ... 12 !) Peon ...... 11 9 ' Sweeper . . ... 12 B

APPENDIX 11.

SOMEPETTY CONTRACTRATES. - i Vnit. ’ Rato. Work. ,- __ &p____ X. A. P. Earthwork by hand- Sand (includinglead of 100 feetand lift of 5 feet) ,000 cubic feet 1 ,i 0

Loanl ,, I ,, 4 S 0

may ), .I 12 0 Leadadditional per 60 feet ...... 012 0 Lift ,, ,,5,, ...... 100 Coucrete,labour only . .l’...... 100 ,, 500 Brickwork ,, ,, ...... tiY0 Erection, riveting by pneumatic machine and caulk-) 1 22 S 0 ing of well-curbs,labour only ...... I ton Xrection and riveting by hydritulic and pneumatic\ machine of maingirders, labour only ... .I l’ainting girders per coat, labour only ....1

Bricks at brickfields, 1st class (98 X 42 X 2!3) . . Supply of standard pitching slone at quarries loaded into trucks- / Minimum rate ...... 100 culicfeet , S 0 JIaxitl~un~,, ...... ,, ;tiso Stone hanclling- Unloadingfronl flats and loading into wagous . ! ,, 0 i 0

Unloading from nypnb: placing in position and 010 0 on bank ...... 1Civeting hydraulicl-inch rivets,labour only . . 100 1.ivctd 12 0 0 ,, pneumatic ,, ,, ,, so0 ” ‘ ‘ i ” ”

Work. - .

Bridge. Standard pitching-Yt.onedelivered at site of bridge from Phudkipur, iucluding allcharges for shift, 100 cubic feet depreciation on permanent way, rolling stock and other plant at quarries and water carriage Ditto from Pakur with rail carriage .... ., ,, Jainti ,, ,, ,, .... Standardpitching-stone in place in the guide banks ...... \jrell-steening,through rate for corlcrete blocks and mass concrete...... Well-sinkingdisplacemeut below bed of river . Well volume, includingsteening. sinking and filling ...... Steelwork including depreciatiorl on plant.aud all charges- Curbs, caissons, holding up rods and bond 1 toll rings ...... Trestles, grillages andfoundation bolt# . Landspans ...... Main girders ...... Coat of main girdera in detail- English price ...... Freight to Calcutta ...... Carriage tosite ...... Falsework ...... Erectionand riveting ...... Scraping,cleaning and painting ... The cost of falsework for the girders erected on the service girder was Rs.49.5 per ton, and for thoseerected on timberatagiug it was Rs. 67.9 per ton. Approuches. Earthwork in approaches, through rate, including, dressing andgraseing, working and depreciation of plant,rolling stock and permanent way, 1,000 cubic feet water-supply, conservancy and sanitation and all charges ...... Earthwork inapproaches done by hand, including all charges ...... Earthwork in approaches done by train. including all clrarges ...... Concrete in lime mortar in minorworks.: including all charges ...... Concrete in cement, ditto ...... Erickwork in limemortar ditto .....

APPENDIX IV.

COST OF HARMWEBRJDGP: AKD TRAINING-WORKS,INCLUDING PRELIM~NAK~ ~:SPKNsk:s, PLANT, AND GENERALCHARGES, BUT EXCLUDINQ LAHDAND I’RRPANENTWAY.

Rupees. T. Preliminary expenses .. 81,901

1V. Bri~l~ework: --

’ ?.M 1’ivt.s .....I /I,95,bW i curl^ BII~caissons 1 ton i 16,05,659 5,856 1274.2 Well-steeniug . 34,66,420 ’ 85.7; loofeetc. ‘]29,71,732 , Well-sinking . . 50,52,116 ’ 14.0 )) ’ 7,10,297 Wellfilling . . 15,01,578 I 23.0 ), 3,45,757 , l’itching round] , 14,45,412 24.6 3,55,538 piers ... ” l

Pier masonry . 6,73,787 ,104-3 ,, ~ 7,02,466 ~ Treatles . . *l 2,821 332.1 1 ton 9,3ti,741 1,antl spans . . .. 1,67,619

Girder8 .... 71 ,51 .S)!)

Mail1 girders . . ~ 18,750 370.0 l ton ~ 69,38,085 Land Sl’&t”u: . . 797 1305.7 ,, ’ 2.43,474 l e- Training-works . . .. /0,91.070 Service-\vt~rke . . 21.67.090

IX. l’lmt I .... 10,90.6iS , .. XIT. Generd charges . .. 1 ...... ,-___-1 24, ti4,340 ‘llutal ...... 2,s3, 72,?40

Deductreceipts on capital accouu~. . , . . 3,95.449 .~

KCL t0tdl ...... %,70,7ti,99 1

Set debit after charging depreciation to works in all cases where particular items of plant were obtained for pitrticulsr works, as, for example, the service girder obtained for girder erectiqn in waterspans.

Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. IV. Ridgework ...... V. Fencing ...... VI...... VII. BallaBt and permanent way . . .. 17,11,490 17,11,490 VIII. Stations and buildings ... 3,39,410 3,39,410 IS. l'lmt ...... 30,90,678 1,15,075 l%,05,7Sr; S...... SI...... XI. General charged ..... 24,64,340 8,21,446 32, S5,786

~- .~ ~ Total ...... 13,83,7S, 440 72,86,989 ,56,59,429 Deductreceipt+ on capital'(;./ -3,95,449 -1,31,816 -5,27,265 account. ....

Set total ...... !2,79,76,991 71,55,173

~ SWQWIWG VARlATtOnS OF COURSE.

I-

... I P

Yl DETAIL OF TIES .-.;~~~~~~~~~~~.... ;” ...... S_ !...... I ,, .

AN K SECTION AA.

APPROACHSPANS, LEFT BANK

G- GENEHAL PLAN OF BRIDGE AND GUIDE-BANKS .F. l

R.L.

DETAILS OF BRACING AT TOP q~ CURE.

CROSS SECTIONAL ELEVATION OF TRESTLE AND MAlN GIRDER. Downloaded by [ University of Sussex] on [13/09/16]. Copyright © ICE Publishing, all rights reserved. bIR R.33 @&.LE S. P LATE S. 'YHfi HARDINGR BHlDM. I ., ..- I.... ,.

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SPAN E16CT60

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