THE GREAT TWELVE MILE TUNNEL.

New Zealand Herald, Volume XLI, Issue 12660, 14 September 1904, Page 1 (Supplement)

THE GREAT TWELVE MILE TUNNEL.

THE SUPREME TASK OF BORING THE SBIPLON. The boring of the Simploa tunnel, the longest railway tunnel in the world, is on the eve of completion. Any day now we may hear that the miners : descending from Switzerland hare joined hands with those ascending from Italy, ■.■while: there is reason to ;.believe that when 1 the meeting takes place the maximum error :^: >':. of direction will be only two or three inches outside an exact: coincidence. There will ' then, of. course, be a, lapse of many months•■'■■•■"• before the railway can be opened. *L /The enormous advantages of the new tunBel are apparent. lb will win back to Prance much of the international ? traffic which has been lost to the railways of that - country since the 'opening of the St. Gothard; and; thus will inflict a heavy blow ta the German railway interest -but, at the same time, it will convert Genoa into a formidable rival to Marseilles in respect of Swiss imports. ' It will effect a considerable saving of distance between the Straits of Dover and the Adriatic, and so ■ will be chosen the East- " era mail route as : between Calais and Brin< disi. Lastly, where traders are it will prove a more economical route than / both the, Mont Cenis and St. Gothard, be- ,1 cause its conditions oJ! grade are so much more favourable. , NAPOIEOJJ'S JftOAD. The Simplon is the fourth Alpine tunnel, and .the second between Switzerland and Italy. The direction of the : tunnel is practically due north and siouth, from Brigue, oh the Swiss frontier, to Iselle, on the Italian • or. from the Rhone Valley to-that of the Diveria.

mvena. • Hitherto, the only means of communication: between the two valleys has been by road through the wild, beautiful, yet, even on ihe brightest, day. gloomy pass in the Lepbntine Alps." The Simplon Pass has been used i->-an international thorougltfare since AD. 206, but the construction of the magnificent road, which still deserves to rank as one "of the world's grand engineering features, was undertaken by Napoleon,' and built between the years 2801-1805. J The road from Brigue to Domo D'Ossola . is 41 miles in length, and attains an altitude of 6590 ft. • The rout© taken by the tunnel • keeps to the north-east oi the road stringing the bow as between Brigue and Iselle... The - mammoth bore is 12 miles 458 yds in length, and: for. seven miles is in Italian tfrritorv The St. Qothard tunnel 13 nine miles &>£*-/;,' long, the Mont Cenis is 30yds short cJ right :' miles, and the Arlbe 4 six miles 404 yds. Each of these tunnels accommodates a double track, ■ and the dimensions ,of each are, roiigklv. 21ft in height by 2Kb in width. ,",'.." It would have bern possible to make a shorter Simplon tunnel,. but a tunnel at a higher altitude would have involved steep approaches, and the lesson; inculcated by the ttiree Alpine tunnels already constructed 'is that the cost of the haulagb of the trains up " the gradients nullifies the initial saving effected by making,the perforation as short as ■■:"■.' passible..: ! :;.•;>.■■■ : ' ; .-'> • * '■-. its cossnccctioTs, However, the Simplon tunnel at the. northern portal is only 22.54 ft, above mk level, or ■ : on the same level M i the 'rails &t Brigue . station, one mile and thtce^uartjjrs-away,"■ , whence, it ascendßifor'j.o,oo4yda;iilrfto gra> ■ di-rt of one in,600 to the sumiiii l m of ') ] 2513 ft. It continues level for 646yd5,; ad;t*r which It descends at one ir, 143 for • 11,028 tod,. Italian portal, which is 2080 ft above ' , , ■; sea level. Immediately oji at each "• ■"" portal.'^ a short •c.tixvo, <)th<>rwi.-ie the tunnel is deal straight; vizi for 12 miles. " ' ./ ItS lii&u ■ """"'' ; dLWt " The Italian very-;different ■ from the Swiss. The extension'of' the rail- '-•'. : way ac Demo., D'Ossola hither ; ; is 20,419 yds locg,vwith a total rise of 117S;ft. : .: Here there ;.tv, no fewer: than six tunnels, ■ ' - with aa /aggregate, length- of Uo67yicsj . ■ and ' one,' the - tong««t ' 3280yda in length, » helical—that; is, 'the train , will "loop the loop," the difference in alti- I tude between the portalsi being 307 ft. . ■ ■ We have seen -that -the .other Alpine " tunnels take a double track; bat the Simplon really consists ■ of two tasraels. each taking 1 a single track. This hovel method of : con" stmction was decided upon owing to the great length of the perforatiosji and its great !•-."■ depth btlow the surface. . The depth of, the ; axis averages 3740 ft, and it attains 7000 ft in ." ■ one place. The problems were how to venti- \ late the bore both during and after construe-; tion, and how to .' obviate the ; exceedingly ; ' , high temperature:? Which would be met with : ; in the deepest p«i:rts.; ~..-■■ ;,. ■• , ; ■ . ~ " JffcESE AIR TOTKJSI TSffi ATJPS. ' ■:, Rightly or wrongly,.the authorities de- ;, :- :! cided" that the foregoing problems might be solved by dividing the work into.twin single,'• , track tunnels, placed 58ft apart axis from-!' 1 axis. The tunnels, therefore, are entirely ■•;- ■■; distinct, save near the centre, where the';':•■ i become one for a distance of 420 yds, in order to give room for sidings and cross-over . ; roads, but throughout they are interconnec- ■.•;.- I:es by transverse galleries every 220 yds. The ■'- - : . idea was that each tunnel might act a& a ven- : ' :> ' tilating shaft for the other. .To begin with, '' : ' however, only one tunnel,* the eastern, would-, '. ibe'given the" normal section for a single tract , —viz., maximum " vg':ii., : 18ft,'"; maximum :-; width, I6ft4in, end area of cross section.' ' '.' 250 square 'fees. ' : The other tunnel would be built in reduced:,; ,; section, and remain so till the gross traffic , receipts should exceed £3128 per mile, when . : : f it would :be enlarged to normal section. .V,: Thanks lie this arrangement of tunnels, the ":'! trains will always run against a draught : : of fresh air. • " ' ■■:- This scheme was elaborated in 1895, when, , ,; the possibilities of electric traction were yet. vaguely realised. 5 The'.latter is certain to be adopted inside the tunnel sooner or later, i and had this been, seen before it would have been simpler and less expensive to have constructed ;.one double-track tunnel ''' Every- •; ',- -~ I, thing connected with the work of construc- [ tion is effected by water-power; both the j Rhone ; and »the Diveria having been. har» . nessed for the purpose. This motive-power, . which represents 6000 horse-power at each' end, could be easily adapted to traction. "'-';,-' - The strata through which the tunnels have' - been. driven were exceedingly hard, Ifreiag principally gneiss and. schist; but the; :';l' Brandt hydraulic rotating drill was never ; r beaten. This beautiful machine indisputably '■-■ demonstrated its superiority to ail others, achieving a rate of progress eqtuvalant to four ••;';' •■ or five times what has ever; beer attained & British tunnels through similar material.; " £.ua>si<-ips and riooDs. No praise is too high for the elaborate aid' > '- perfect nature of ithe mechanical, sanitary, and sociological arrangements - undertaken! 7 '■< Vl for the welfare '; of the Simplon' miners. Inside the tunnel, the temperature, which has" been recorded to attain 121deg k Pahr> on the''•''"•'•? rock, is cooled to a maximum of 77deg. by means of eprays oil glacier water, filtered be- ' fore use; and relays of fresh air, which are passed gh sprays and dried by wire gauze screens before retching their objective. " The foul air is eahwwted by the great fans supplying the fresh, to the volume* of 60,000 '■ cubic feet per minute; and horse* were early ':"■■■ -r banished from the galleries, As the exhalations ,- from their bodies vitiate the - atmos- . phere. Perfect sanitary and laundry arrangements are found outside. " The contractors for the whole colossal undertaking are Brandt, Braudau, and'. Co., of •' ; Hamburg. According to the terms of a re- i, ■ vised convention,'; the first tunnel must be : ready for traffic and the second completed in; v reduced section by , April 30, 1906, ,in J con- ': sideration of the sum of $3,120,000. Active operation were .commenced in August, 18S8; ; . : .■;.-' i aadiliave'contintied'WiinterrvfUulx night ' and day ever sine;?, ■)"■ y ; . ,■■ . ■" •-'■. .■■■■ '" : '-••'-■■■' '• ■','-■