TUNNELLING METHODS

Otago Daily Times, Issue 20283, 16 December 1927, Page 12

TUNNELLING METHODS

AN ENGINEER'S CRITICISM. REPLY BY MR F. W. FURKERT. NEW ZEALAND SYSTEMS DEPENDED (Special to Daily Times.) WELLINGTON, December 15. The Chief Engineer of the Public Works (Mr F. W. Furkert) replied to-day to state, raents made in connection with New Zealand tunnelling methods. - ‘ There is no means of checking the qualifications of the gentleman who supplied the information," said Mr Furkert. “ His ability to make tunnels may be accepted or not according to the knowledge of the reader as to the reasonableness of his statement, but his ability to observe and record his observations is evidently hardly up to the the average. Touching his suggestion that the Public Works Department should immediately send abroad one or more of its engineers to specialise in this branch, he was probably not aware that a great many of the engineers in the Public Works Department have had experience in tunnelling abroad, and that when pitted against the finest tunnelling companies on the Western front they left a record of which no country need ever be ashamed. “ Concerning the tunnel on the Westfield deviation, the design is in accord with the practice followed by tunnel en gineers wherever the circumstances are similar. Regarding the Tawa Flat tunnel the engineer in question evidently did not absorb the information which was conveyed to him, namely, that the tunnel was being constructed by contract, and it was purely a matter for the contractor himself to decide how he would carry on. It is quite easy to make airy suggestions that an endeavour should be made to obtain the benefit of modern methods. One of the principal reasons for calling for tenders for this work was to ascertain whether there was anyone either in New Zealand or outside who was prepared to construct th e tunnels required by any methods, antiquated or otherwise, at a lower rate than that at which the department could carry out the work with its own employees, or by means of piecework, under what is commonly known as the “ co-operative system.” ‘‘The suggestions made as to the pro-bable-times for completion are too absurd to warrant serious consideration. The contract time fixed for the Tawa Flat tunnel is three years, and given an adequate supply of labour the work can be completed by the ‘ antiquated methods ' of the Government in that time. There is no analogy between the Westfield deviation tunnel and the Tawa Flat tunnel. On the Westfield deviation the tunnel was not the governing factor in tho time of completion of the railway, and there was no advantage to be gained in adopting a method of working which would have resulted in its being completed long before it was wanted. “ The statement that the same method is to be used on .the Tawa Flat deviation may or may not be true. Certainly the engineer critic could not have known, because the matter is still in the minds of those who happen to be the successful contractors, but speed will be an essential feature of the Tawa Flat job, because on the work the time for completion of the tunnel is the determining factor, while the reverse was the case at Westfield. “ The writer of the article states that the Tawa Flat tunnel is being carried out by co-operative labour. This is not correct. Public tenders were called for this work, and H is being carried out by the successful tenderers. The engineer in charge of it gives an emphatic denial to the statement that he said he had to rely mostly on th e men under him. The engineer states that the subject never arose in the course of conversation, so that it is quite evident that it was not the Governmeht’s engineer’s leg which was pulled in this connection. To suggest that the method by which the contractor is putting through the bottom beading of the first Tawa Flat tunnel should only be used in absolutely loose sand indicates that either the writer of the article was misunderstood by the reporter, or else that he intended to create an entirely false impression, for it is hard to believe that anyone who has ever seen a tunnel excavated coma suggest that the contractors’ method at Tawa Flat could be used in loose sand or very wet day. It I s quite an eas; matter to prophesy as to the rate of progress which mil have been experienced after the expiration of several years, out the department at the present time prefers not to prophesy. The specifications, which are spoken of as being forced >n the contractors, ar e only specifications as to the character of the work which the, contractor must supply to the Govern ment on the completion of his contract. The methods of tunnelling must be decided upon by the contractor himself- It is news to the department that the question whether you should use a one-track tunnel or a two track tunnel in any way depends upon the ground to be passed through. If the Government desires to have a double track railway it seems self-evident that it must have a double track tunnel, whether or not this s through hard rock, soft rock, sand or clay, or any other material. He asxs the question whether the workmen ire willing to be taught modern tunnelling methods. I think the answer to that is that New Zealand workmen are amte as anxious for tho best methods as che workmen in any other country, and anyone who can show them a method by which they can do more work and consequently make more money than they do at present, will be hailed as a benefactor. If the gentleman in question thinks that the whole system of tunnelling is absurd and costs three times what should, whv does he not put in a tender to do the work at, say, 50 per f-ont. below ;he engineer’s estimates? He will then be quite sure of getting the contract, and will be able to make 100 ner cent, profit. ‘ “Several of the senior r-igineers have within very recent years been abroad, and have investigated tunnelling methods in North America, the British Isle=. Europe, Africa, and Australia, including various types of ground of widely differing characteristics, and they are quite satisfied that the statements contained In the article under review are inexplicable. “ Coming now to the cost of- some of the great tunnels of the world, these ire as follows:—The Hooaac tunnel, in the United States, double track 4.7 miles long, cost £B2 per foot; the Loetshberg tunnel, in Switzerland, also double track cost £42 per foot; the Caversham tunnei, in New Zealand, £9, double track :ost £2O per foot; and the Chain Hills tunn-n, New Zealand, also double track through difficult ground, some oarts of it being extremely difficult, cost £69. ” Coming to the single track tunnels, the Simplon tunnel, in the Alps, which, when originally driven, was a single track tunnel, cost £49 per foot, while die Otira tunnel which ranks about severdn of the world’s tunnels, cost under £3i per foot. Of the shorter tunnels the costs in New Zealand have been evu.y reasonable For instance, t’ Powhakn roa tunnel on the Main Trunk, cost £o 6s 6d per foot, and the long tunnel on the spiral cost £8 8s 3d per foot. Some of the very difficult tunnels on Ihe Mid land railway between Springfield and Broken River coat slightly under £9. Many other instances might be given. Subway tunnels now being driven in New York are costing double New Zealand prices for equivalent work. It will he seen from this that whatever mav be staled of the methods, very little ndver-e criticism can be marie ns to the cost, and it is always understood that ironrl methods are reflected in reasonable costs and poor methods result in expensive work. The costs of New Zealand tunnels seem to ' speak for themselves.”