THE MIDLAND RAILWAY

Hokitika Guardian, 3 August 1923, Page 1

THE MIDLAND RAILWAY

Airmnrs pass tunnel. (By V. 1.. Newnham. A.M.1.C.E.) Xext to a jirolilic soil ami the possession of great natural resources

' otherwise there is no adjunct of material progress that is sa generally im- ’ poriant and exercises so vital an inlluonce on national characteristics as the growth of the railway system. This being so. the Dominion of New Zealand may fairly claim to he supplied with tiie principal rer|iiireinents for wellbsing and prosperity, inasmuch as nature lias provided the former and the enterprise ol its inhabitants has attended to the latter. Among the colonists in the early day* of Xew Zealand there were many who had a keen perception of the advantages that would attend the introduct inn of railways into the new country they were helping to found. The progress of colonisation was, however, naturally somewhat slow in those days, and it was not until Infill that a contract me let fur the ciuisnietion e.f the lirst Xew Zealand railway: this was between Christchurch, the chief town of Canterbury, and Lyttelton, its seaport. Since then railway construction .has progressed as rapidly as the financial position of the country and the great natural obstacles encountered have allowed. At the present time there are about three thousand miles of line open for trallic, and a largo number ol new lines under cons'truelion. In the Middle Island of Xew Zealand for South r*land, as il is more commonly called! the great obstacle to railway communication between the fertile plains of Canterbury, with its port. Lyttelton, on the east coast, and tile timber and coal lands of 'Westland on the west coast, has been the high mountainous ranges of the .Southern Alps, which run parallel with (lie east and west coasts. The South Island is roughly about five hundred miles in length, with an average width of probably one hundred and twenty miles, and it is divided for almost its entire length by this alpine range. Some of (he stunmils of ihe range reach a height of from 10.000 ft. to 12,000 ft, Mount Cool:, the highest point, rising to 1.2. A 11)11 . From (lie earliest days of colonisation the fpiestion of railway communication between Christchurch, on the east coast, and Oreymoui h, on the wesl coast, had attracted great attention, more especially among the residents of Canterbury and Westland. (Jreyniontli is a bar harbour, difficult to work, and seldom if over visited by

steamers from Europe ot' America ; l»u( Lyttelton, llio port of Christchurch, is :i common port of discharge ami loadin': for sUrli vessels. Surveys and explorations for the purpose of ascertaining the best route over Hie mountain-ranees were put in hand al an early dale. In IM(M Mr Arthur Dudley Dobson made a survey for a 1 read over the mountains from Chrislehureli to Greymouth. This was taken over a pass called "Arthur's I’ass,” in his honour, and runs down the famous Otira Goage. The survey of this road and its suhse(|iient const ruction omdiled a eonsiderahle amount of useful information to hi’ collected in furtherance of tlm projected railway. llet ween 1 sirs ami I .'■•S3 numerous surveys of proposed routes were made, te most notable hemp; the Cannibal Gorge rouie, running from C'ulverden. in Canterbury. to fteefton, in West- j i land: the 11 11 rim ti i Gorge route, from Waikare to Jackson's; and the Ar-j thnr's Pass route, running from Springfield, in Canterbury, to Stillwater, near Creymouth. In Issf! a Itoval Commission was set up by Parliament to decide oil the best route for the proposed railway, and the Ai l bur’s Pa-s route was finally adopted. The line from Christchurch had already been constructed as far as i-lnrimdiehl, and from Creymouth to Stprin"field Ihe route was roughly as follows: ft ran from Orcymoulh up the valley of the C rev River to Uruimr-r----lon and Stillwater Junction, and thence up the Arnold, and round the northeastern side of Take llrnniier, through a natural depression, into the Tereniaknu Valley; iiji the Teremakau river and ils tributary the Otira. to Otira; from Otira over Arthurs Pass to Pealev Flat (or "Arthur's Pass," as i( is now generally called) : from Healey Flat down the Healey Valley to file 101 l hank of the Wnimakariri river, then crossed to the right hank, which it descended as far as the Cass River, where it left the river and made for the saddle of Mount St. Poniard, whence il descended by the long valley of Slovens Creek to Ihe Waimakiriri Gorge; thence down this Gorge to Springfield, and across the plains to Christchurch. , At that time the intention was (o , construct the line on a l-in-15 grade , over Artliur’s Ha -s, using a cent re-rail, , Fell svstem. The summit of Arthur's .

Pass is about .‘l.oooft above son-level. As soon as the Arthur’s Pass route was finally adopted, several influential Xew Zealand gentlemen formed what was known as the Chrystall Syndicate, to push ahead with the construction of the Midland Railway, as it was now generally called. They entered inio various railway-eonst ruetion contracts with Cie Xew Zealand Government. Tn 1 S s (i the Chrystall Syndicate was merged into the Midland Company, with a capital of CIOO.OOO. The Xew Zealand Midland Railway Comnanv T.imiredl was what is general ]v known as a land-grant rnilwayroiistruetion corporation, similar to the great railway companies of Canada, and was founded in Fill"!and by a syndicate who took over the contract ol tlm Chrystall Syndicate. Those contracts wore subsequently annulled, and a new one. dated Urd August. ISSS. was entered into between the Xew Zeeland Clovernrneid and the Midland Company. That contract provided, among other matters, that the comnanv should construct a line from Springfield, in Canterbury, to Rrnnnerion, near Oreymoutb. in estland. ecef.oh.yFn fiVgOn RTl'vfZc ?Vv CJ-ua As an inducement to the company to bifid the railway, all Crown lands remaining at the time of the signing of

the contract in the provincial districts of Canterbury and Westland and Nelson (aggregating about (5,000,000 acres and of an estimated value of £3,150,000) were earmarked and cut up into blocks, each block being valued in a schedule attacked to flit; contract, and none tit less than 10s per acre, 'ihe entire line was divided into sections for the purpose of allocating the proportionate estimated cost of the

construction of each particular section; the company, upon completion of a section, being enabled to select blocks of land, upon the basis of 10s worth of land tor each L'l spent upon the construction of the railway. Between 18SIJ ami ISHu work pro-

ceeded vigorously, hut when about thirty-live miles ot the line had boon completed the physical difficulties to be overcome were found to he so great that the company shrank from attempting the apparently impossible, and accordingly the ambitious idea was abandoned. The result was that the Government took the railway over and determined to penetrate the mountainehains al all hazards.

From J 895 construction work was pushed ahead on hot It sides of the mountain-ranges, and in H'OO a committee of engineers was set tip to consider the best means of crossing the actual dividing-range—whether to adhere to the original proposal of a. l-in--15 grade over the range, or to have a long summit-tunnel. The comm it toe decided in favour of a .summit-tunnel about six miles long, with a grade of approximately 1 in 37. In Bifid Mr V. G. llogtic, an eminent American engineer, was called in by the New Zealand Government, and after considerable investigation recommended a line with a shorter summittunnel on a grade of 1 in 32. As ho considered a lute with a summit-tun-nel on such a stoop grade was quitu suitable, further surveys were made, and a line with summit-tunnel on a grade of 1 in 33, and in . ils present position, was finally located. This proposal was submitted to .Mr Rogue, who

confirmed the recommendations of the local engineers, and it was finally decided to adopt this route. The eastern end of the tunnel is al the summit of the line between Christchurch and Greymouth, and is in the valley of tile Ifealey River, near what is now known as Arthur’s Pass Station; and the western eml is in the gorge of the Rollcston River, about three miles and a half above Otira Station. Otira is about fifty-two miles from Greymouth, and Arthur’s Pass is about eightv-five miles from Christchurch.

The location of the tunnel having been decided, final surveys were at once made for the purpose of carrying out the construction. A line was ranged out over the mountains from one end of the tunnel to the other, a series of trigonometrical stations were established, and precise levels were carried from one side to the other Owing to the mountainous nature of the country and (he severe weather experienced at. times, the whole of this work was carried out under extremely trying and difficult conditions; hut, as will he seen later, it was done with extreme accuracy. The surveys completed, plans and specifications were prepared, and on the 1211 i August, 19l)7. a contract was let to Messrs J. 11. Mr-Lean and Sons for the sum of £599,791, the time for completion being fixed at five years—a very optimistic estimate as events transpired. 1 til April. 1008, the work of driving j the bottom heading was commenced at the Otira eml ; and on the 51.1 i May, Sir G. Ward, ns Prime Minister, fired the lirsl shot at the official opening of the work. On the Ist July, 1909, the buttom heading at the Arthur’s Pass ■■lid was cnmmciiced.

Alter spending about £250,000 mi plant and material, and making great efforts to proceed with the work, the rout rail ors found that they could not possibly finish the work for the contract price. They informed the Government accordingly. A Parliamentary Committee looked into the whole position lis.d'ure releasing Messrs McLean and Sons from the contract, and came to the conclusion that, as the Arthur’s Pass Tunnel was a I’alioiiat work which ought to lie completed, fresh tenders should he called, and the Public Works Department he instructed to continue the work meanwhile. It was fairly evident t lint no private contractors would face ilie task which ihe original eontractors had found so difficult, consequently the responsibility for the work was shouldered by the Public Work' PeparLinoiii, which has now brought ii to iinalit v.

The summit-tunnel, though the most notable work in the line, is hut one of many notable works, for the bridges and slimier tunnels compel jusi as much attention. To give some idea of their frequency and character it may be mentioned that, in a short length of nine miles, there are three high steel viaducts, one of which carries the rails •Tilill above the Moor of the gorge, and no less than seventeen short tunnels, the longest of which is about li,oooft , while there is scarcely a mile of level in the whole line. A tremendous amount of work has also been done in protecting the railway embankments from mountain torrents, which run at a terrific pace in Mood-time.

The exact length of the tunnel is :> miles fib 1 yards, all on ihe straight, with a grade of 1 in MM. or 2tt per chain, rising from about 1,5851 1, above mean sea-level at the western end to a heigh! of 2.‘155 ft above mean sealevel at Ihe eastern end—a rise of 850 ft. If will carry a single-track line of lift Oin gauge, which is the standard gauge of the Xew Zealand Government railways. In cross-section the clear height above rail-level is 15ft Gin, with a maximum width of 15ft. The. tunnel is lined throughout. The sidewalls and footings are of mass concrete, and the arch is formed ol concrete blocks. F.xcept where the ground is very had the mass concrete is carried part way up the arch, and only a few rows of

Mocks are used. The tunnel is in solid rook except for a few hundred feet at the portals. Thr.se who expected some interest tug geological discoveries ns a result of the big drive through the rifturc have been disappointed. The rod; was found to l o monotonously alike right through, varying only in degree of hardness. The rock lies mi it- edge in more or less vertical beds of greatly varying thickness. whoso strike is more or less parallel to the tunnel. The rock i< jointed in all directions and is fissured badly. It X of such, a nature that explosives can be used to great advantage, but it is gritty, and hard on the drill-steels used for boring the holes for blasting. Tn places it changes abruptly from extremely hard sandstone to medium sandstone and indurated slaty shalo. s’.m-r of tli» rock was so hard that the greatest difficult',- was experienced in hardening the drill-bits so that they would stand the wear and not break. The greater part of the tunnel was, however, fair boring. Temporary timbering was used

throughout to prevent fluking of the rock-surface, and fairly heavy timber was necessary in some of tiro worst places where faults in the rock-struc-ture were encountered. The ground I was sometimes dry, commonly wet, and occasionally very wet ; hut the tunnel was pierced without striking any very great volume of water necessitating special methods such as were employed in the construction of the Simplon and other long tunnels. The greatest flow of water was about 3.001) gallons a ’ minute, but as the lining was completed this was considerably reduced, and the present flow is about 1,500 gallons a minute. The greater part of (he work undone up-hill from the lower or western end, on account of the assistance of the grade-in getting rid of the excavated malarial, and because of the heavy pumping required to drain the tunnel at the eastern end until the headings met. The excavation was carried out by the bottom-heading method, followed iy an enlargement to full section: i.c., a bottom heading or drive about Bft. high and 10ft. wide was first driven; when this had advanced far enough a top heading was driven, followed by the breaking-down and excavation of the arch, walls, and footings. This method allowed more men to he employed in the workings than if the tunnel had been excavated in one face, and is in general use, except that sometimes the top heading is driven tii st. The best average rate of excavation was 131 ft. per day for twelve consecutive working days. The headings were timbered a.s required, and when the full section was excavated it was also timbered and lagged ready for concreting. The concrete lining of the tunnel was kept as close to the full section excavation as possible. All concrete was machine-mixed, and was in the proportion by volume of one part of cement, two parts of sand, and iivo parts of shingle. The concrete blocks in the top of the arch were made outside tlio tunnel, and allowed to mature lor three months before use when possible. About half the stone for concrete aggregate was obtained from rock excavated from the tunnel, and the remainder from deposits near each end of the tunnel, flood sand was scarce, and grinding machinery was used for a time at one end. Most of the stone and sand obtained outside the tunnel had to lie washed, and the cost of the connote aggregate was high. The drilling of the holes for blasting was all done by drills operated by. compressed air. 'Two or three drills were used in each of the headings and others elsewhere as required. The compressed air was convoyed to the working-face* Uv a 5 inch main at one end and a 0 inch main at the other end. Power for the air-compressors, for lighting purposes, for driving the elec-tric-mine locomtoives. and for driving the miscellaneous machinery wos obtain'd from hydro-electrie plants at each end of the tunnel. At the western end the plant generated (500 horse-power at 500 volts, direct current. The plant at eastern end was of similar capacity: and before the bottom headings met. power for operating the pumps for pumping water out of the eastern ljottom heading had to he supplied by the plant, in addition to the power required for compressors, locomotives, lighting. etc. The haulage of truc ks from the work-ing-faces to the completed part of the tunnel was effected liv means of compressed air-driven winches and wire ropes. The haulage of the excavated material from the completed parts of tin tunnel, and the haulage of timber, concrete etc., into the tunnel, was done liv means of 10-ton electric minelocomotives. These ran on a "2ft. <>in image line, and in the completed porjons of the tunnel power was taken ■rom a bare overhead troll.v-wiro, in the iMtal way. As these locomotives often 1

worki'il beyond tin* completed portions n ilio tunnel, cat'll locomotive was fit-' till with a drum carrying an insulated cable, timl a. rewinding motor and brake. The cable was hooked to the end of the trolly-wire, and enabled the locomotive to run right up to the work-ing-races if necessary, and avoided the difficulty and danger of providing a susovndod bare trolly-wire in the uncompleted part of the tunnel. In a tunnel live miles and a-qiuirter h ng adequate ventilation is absolutely necessary. In Hie Arthur's Pass Tunnel ventilation was elleeted by a system of exhausting the air from the

orkintr-faees. pure air being thus induced through the completed part of the tunnel. A Knots blower having a eapaeitv of -I.IVK) cubic foot tier minute na.s installed at each end of the tunnel, the air being exhausted through it 1 Gin. riverted steel pipe, which extended to the completed parts of the tunnel. At the Otira end, as the working-face advanced, the blower at the end of the tunnel was found lo he insufficient, and a ''booster” blower was installed about a mile anil n-linlf from «tlie tunnel-por-tal. The working-faces were further ventilated by the exhaust air from the air-drills. When the work was first -tarted ventilation was effected by releasing compressed air at the lace, thus driving out the impure air along the tunnel. I hi- meant the fouling of the line along which spoil bad to he hauled and ti change to the exhaust svstem was made by the Public A\ orks De-

pnrtinent. I,i;1 1 1 iim outside mill in the finished purls nf tlin tunnel tv:is by electric in-ciUiilc.M-ent lumps, using l wo 250-volt InmpH ill series nt Piicll point. I his voltage wns too high for lighting m tunnel working-places. ami miners acetylene hand-lumps were there used, one to piicli mnn. At both ends of the tunnel wider for drilling, drinking etc., was supplied to nil faces. The men employed nt the tunnel were housed, and change-rooms. Path nuns. etc. wore provided nt the portals. A hospital was erected and equipped at Otirn. mid at the Arthur’s Pass end arrangements were made for special trains in i use of accidents. ’|'lie progress of the work was slow, and the estimated time for completion, and also the estimated cost, were considerably. exceeded. A large part of the work was done during the war period. Wages rose 50 to 00 per cent. The rost of the material was in some casers more than doubled; cement, for instance, rose from £-1 per ton to £0 and CIO per ton, and was at times almost unprocurable. In fact, on one occasion the concreting-work had to be stopped for a short time ns no cement was available. The supply of skilled underground workers was never equal to the demand, and. although good wages were paid, the works wore never more than half-manned. Tn parts the roc 1 ' proved much harder than was anticipated. and at different times falls of rock at the parts previously mentioned delayed the work. As previously stated, the work wa< taken over from the contractors by i h r Public Works Department in December. 191 "2. At that time the bottom headings had been driven for a leugie of two'miles and a third, ai d the tunnel was completed and lined lor about a mile and tliroc-t|uarlers. From tha f time steady progress was made. Fn the 7th Mav. 1918 the men nt the Arthur’s Pass end of the tunnel beard the sound of the firing of the t barges used in the bottom heading at tm Otirn end. Keen interest was aroused; and on the 29th .Tune the sound "! too rock-drills working on the face at tty Otirn end was heard by t.ie Art am s Pass workers, who were about a wav. Shortly after tins, on the -Ota Tulv the bottom headings met—3 'miles OS chains 10 links having been driven from the Otna end. and l mile 37 .chains 4-1 links from the ether end The meeting nr the headings showed that the surveys had been ina.de am the tunnel driven with remarkable accuracy. the difference between the actual length and the calculated length was 36in. the difference in level was onlv 1 jin., and the alignment was extremely accurate, being only ?.in. out. Dy way of 'comparison: fu the Mount

C'enis Tunnel, seven miles and it hall' loi'g. the error in direction was found t'i be nil.Mhe error in levels to be Ift. ami 1 1 10 actual length to be 1011, in excess of the calculated length. On the 2 1st August, 191 R. the final barrier in the bottom heading was shot away by a charge fired by Sir William I'Ynser. then .Minister of Public Works, and about three years afterwards the whole of the excavation and lining was t mipletod. Arthur’s Pass Tunnel is the seventh 1 ugest tunnel in the world, and the longest in the British Empire.

Serious ami fatal accidents have been law; there havf lieen occasional falls of i(,dc, as mentioned above, delaying the work and increasing the cost. At the east end, for I,oooft. or more from the portal, the. tunnel runs close to the I liver, under a, steep hillside, and with j very little cover in places. In May | lino, at a point where the arch was i within 30ft. of t!ie surface, and the j i of was very thin rock covered with clayey gravel, the weight of ground broke through the timbering of completed excavation feir ottft. along the tunned, and ran to the surface. Some men were caught in this fall, one of whom died later. Two men. free and unhurt, w ere imprisoned in the hot tom h ading heyond the break for four days, while an adit was driven from the river side to g-U them out. Conversation with them was carried on throned! tin bin. air-main, through which also J ih"v were nrovided with dry clothes i and food. They were none the worse for their experience. Owing.to the steep grade and the difficulty of dealing effectively with the smoke from steam-locomotives, it was decided to electrify the tunnel. Several schemes were considered—hy-dro-electric power against steam for the generating plant; the electrification of a considerable length of the. line on each side of the tunnel; the electrification of the tunnel only; and several other alternatives. Tt, was finally decided to electrify the track from Otira to Arthur’s Pass, a distance of about eight miles and three-quarters. The generating plant is steamdriven. and the power-house is at Otira. ’ldle, system used is 1,500 volts direct current, overhead contact. Three marine-type water-tube hand-fired boilers are installed, and the generating-sets consist of two geared turbine-driven generators, of 1,(500 kilowatts capacity. In the future, when power becomes available, it is intended to link up the line with tlio hydroelectric system, and to use the steamplant as a stand-by. The power house was built by the Public Works Department. The construction of the reservoirs and pipelines for the. water-supply and powerhouse. and the laying of the rails for the electrified portion of the line, were also carried out by the Department. Two contracts wore let for the rest ol the work—one for the installation of the boilers, and another for the prime movers and the electrical equipment. The electrical-equipment iontract included ilia supply and installation of the generating sets, locomotives ond all overhead work. Climatic conditions have been against (lie rapid completion of the electrical work. The summit of the line is *2.-135ft. above sea level. Otira is at an elevation of 1.200 ft. above sett-level. The rainfall is very high, the average annual rainfall being lOoin. or over j Kilt. Considerable snow also falls dor- j ing some winters, a fall as much as sft j having been experienced at Otira. | Temperature records have been kept . near' the tunnel portal at the Otira i ■nd. The lowest temperature recorded was 11. degree* Fahrenheit, and J highest 82 degrees Fahrenheit. The ■ thermometer remained below I reeving | joint for one period of thirty-six conse- j olive days (thermometer outside in r he .shade!. . f In addition to the extreme cold and , he intense rainfall, gales ol great vio- | cure occur in the district. Notwithstanding the difficulties I which have had to be overcome, ami a the adverse climatic conditions. the jj clcti'ieal work is practically completed. j