PERILS OF TUNNEL-BORING

Hawke's Bay Tribune, Volume I, Issue 185, 22 July 1911, Page 2 (Supplement)

PERILS OF TUNNEL-BORING

• Another of Europe’s great railway tunnels has recently been bored, ami I some two years hence it will be opened ! for traffic. Those travellers who will j then find the journey to Italj- considor- • ably shortened, thanks to the Loetschi berg Tunnel, will probably give little | 'need to the perils faced by those who ! constructed it. j Art one time it seemed likely that ■ the tunnel would have to bo abandoni ed. and as a matter of fact work was ■ suspended for seven, months. Owing i to some miscalculation the gang at ' work at the tunnel face broke into j tho Kander river nearly two years ago, I und in tho rush of water and sand i that followed five men lost their lives, j This added fSILOOC 1 to the cost of ' th? boring and mad? it longer by at i least hali-it-mile. as the holo had to be | walled up and nearly a mile of tunnel i abandoned. Resides this the course had i to be altered somewhat.

i Water was only one of tho troubles that beset tho builders of the Simplon Tunnel, although the inrush of both i hot and cold springs wa« so great that ! special channels had to be blasted out ! of the rock in order to carry it away 1 safely. j In the middle of the boring the heat ! was so terrific that tlie workmen could j rot stand it until the air was cooled I by sprays of the ie<~eold water from : tho springs. Then the pressure of the 1 rock above was so enormous that it 1 threatened to flatten out the tunnel ! until piers of steel embedded in conj crete were placed dose together. Groat i baulks of timber were splintered into i mat hwood. \ While boring the Mount Orso Tun- ; ncl in Italy the workmen suddenly ■ broke into a vast cavern over 130 feet ! deep and some 200 feet across. In or--1 dec to continue the boring a smaller 'I tunnel was made round the eave, but 1 tho engineers have net yet decided | whether this chasm will be bridged or i filled in-

Thanks to the perfection of modern engineering appliances, tunnel boring is safer than it used to be. By moans of the shield and air-lock water can be kept out by compressed air, but, occasionally the up-to-date .methods are themselves responsible for accidents. On mor.’ than one occasion a workman has been killed by leakage of an ele trieal current, while when the Tauer 11 Tunivd in the Tyrol was being construct'''! three mon . were killed and a number rendered insensible by the fumes from a motor en-

gine. Great ns are th' perils encountered f;v those who tunt.,<?l through the heart

of mountains they are infinitely worse when the bed of a river is bored. In spile of the use of compressed air in the shield water may break in, while if th-? alteration in the pressure of the. air-lock is not changed very slowly the d.-r.diy eais-on di-eime may bo contracted. Those who wat-Aed the construction of the Bakorloo tube under the Thames at Charing Cross may have seen air bubbles rising to the .surface, showing that th-.? compressed air had forced its way through the liver bottom. The pressure blew a hole m th.-, bed at Blackwall when the tunnel was b ‘ing made. To prevent this happening tons of eaith and ballast ar* dumped into -lie water above the boring, but this dr,' little good when the Hudson river tunnels in New York were being driven.

The clay of the river bed was as thin as soup, and no amount ol rubble prevented this from _ percolating into the working, so a series of blowpipe flames were directed against thif semi-fluid clay, thus eff<*ctiiallv baking it into brick. To keen the shield cool, jets of water were directed on to it when the blowpipe? were at work. In oide*- t-> bo on iho spot in case of accident, doctors were always nt duty either in the entrance air lock or close out-ide. No doubt the worst tunnel to construct in. England was that under .the Severn. Tim? mid again springs vore encountered, and the men had to mil for their lives, and lor more* than a y**ar the pumps dealt with an average of 21.000.01X1 gallons daily. So great was the drip or water tri'iii the roof that until the vL-clric light was irstalbd the mon had to work almost in darkness. Waterproof overidls were a necessity rather than a litxinv. while ilio iv’ii hail to work tinder rent- houses ci corrugated iron to keep them di v.

Even in prosaic London exc-i voters have broken into underground lake?;, and when the Thames 'I mmol was built Brunel nearly lost Ins life *<h -u tin* roof gave way and the workings were filled with n titer