532 REPORT— 1892. 



Shield Tunnelling in Loose Oround under Water Pressure, with 

 special reference to the Vyrnwy Aqueduct Tunnel under the 

 Mersey. By GtEORGE F. Deacon, M.Inst.G.E. 



[A communication ordered by the General Committee to be printed in extenso among 



the Reports.] 



It is impossible, within the limits of a British Association paper, to give 

 anything like an historical account of the tunnel which has recently been 

 successfully completed under the river Mersey for connecting the Lanca- 

 shire and Cheshire portions of the Vyrnwy Aqueduct. A romantic and 

 instructive account might well be written of the battles with the elements, 

 of the repeated failures and successes, and of the hairbreadth escapes, 

 with ultimate pronounced success, which attended this subterranean and 

 subaqueous work. 



From first to last the operations, including stoppages, occupied forty- 

 seven months. At the end of twenty months the first contractors had 

 completed the work of driving and lining the tunnel from the Cheshire 

 shaft to a distance of 57 feet out of a total of 805 feet required, when, 

 having also sunk the greater part of the Lancashire shaft, they ceased 

 work. The second contractors, rather than reopen the disturbed ground 

 of the old workings, began, with permission, at a higher level on the 

 Lancashire side. At the end of a further period of twenty-one months 

 they had driven and lined 182 feet from the Lancashire shaft. They 

 then relinquished the work, and it was taken up by the Corporation of 

 Liverpool, most of the men being retained and one of the contractors 

 continuing to superintend them. After this the remaining length, about 

 620 feet, was driven and lined in four and a half months, the maximum 

 progress being 57 feet per week of 110 hours. 



In the case of the first Thames Tunnel the practical difficulty of 

 carrying on the operations successfully, either by contract or piecework, 

 impressed itself upon the mind of the elder Brunei. It was, indeed, the 

 only evil against which, with marvellous foresight and ingenuity, he 

 could not make provision. The same sort of difficulty has very forcibly 

 shown itself in this case, and there appears to be no doubt tha.t if the 

 work had been taken up in the first icstance on the basis ultimately 

 adopted, the whole of it would have been as successfully and economically 

 performed as the last length of 623 feet, which was carried out, without 

 the intervention of a contractor, in four and a half months. 



The general particulars of the Vyrnwy Aqueduct Tunnel are as 

 follows : — 



Lancashire Shaft — 



Depth 



Outside diameter ..... 

 Inside diameter ..... 

 At junction with tunnel, outside diameter 

 ,1 „ inside „ 



Cheshire Shaft — 



Depth 52 6 



Outside diameter 109 



Inside diameter 9 9 



At junction with tunnel, outside diameter . . . .15 

 ,, inside ,, . . . . 14 



