Work on East Coast Railway

Hawke's Bay Herald-Tribune, Volume 81, Issue 46, 17 November 1937, Page 3

Work on East Coast Railway

Our Own Correspondent.)

GISBORNE SECTION Shortage of Steel Hampers Progress MINISTER'S REVIEW

(From

WELLINGTON, Last Night. Tbe work which was done during the past year upon the NapierGisborne railway was the subject of review by the Minister of Public Works, the Hon. K. Semple, in his annna.i statement presented to the House of Representatives to-night. The Minister said that a total of 1300 men were employed on the line and that the Railway Department now operates a service from Napier to Putorino, while the Public Works Department controls a train service from Putorino to Wairoa. Although the sections are separately controlled, goods aro railed at through rates. That service was already providing a muchneeded facility, and the extent to which it is being availed of indicated tbe need that existed for rail connection in that locality. North of Waikokopu, which is already linked witli Wairoa by an existing line, work is proceeding expeditiously at all points on to Gisborne. Eeferring to tho northern section of the line, Mi Semple said that the general plan of construction aimed at the earliest possible completion of the major tunnels and those bridges which would hold up progress if left until reached by the permanent rails. The large tunnels occur in the middle section of the route, while the bridges are .mainly on the end sections. "Earthwork," he said, "is not a deciding factor in the date of completion. Although uncommonly heavy in the middle section, and for a lengtli of one mile along the Waikokopu Bluifs, work was opened up on a great number of faces when tbe tunnel service roads were completed in the early stages of construction. At only a few points are the individual cuttings and lillings of such dimensions as to need special methods to expedite progress, and in each case the job is being well handled by up-to-date Disel-powered machinery, which reduces years to months in the construction schedule. "The construction of service roads under the general plan mentioned above made possible the prosecution of work along the whole length between Gisborne and Waikokopu. Shortly after resumption of activities 1,000 men were systematically placed thrtifighout the whole length of the line. Owing to difficulty in obtaining delivery of tunnelling plant ordered from Britain tnere was some delay in getting the larger tunnels into full swing, but this is now mainly overcome, and the underground work is moving ahead in a convincing manner, with eight separate tunnelling parties workmg at different points." Progress of Work. The Minister gave the followlng particulars of work under various headings: — ■ Fencing: Thirty-two and a-half per cent. of the total length of 56J miles has been completed. Much of the rexuainder is being left until * the high batter slopes of cuttings anc^ embankrnents have become consolidated. Culverts: These vary in eize from large reinforced-concrete ones of 80 square f eet cross-sectional area down to lit.-diameter pipes. The total length of all culverts installed is 4,044ft., representing roughly 85 per cent. of the larger and more expensive types and ■ about 55 per cent. of the smaller pipe culvert class. Most of the culverts remaining to be laid will not be needed until the work is further advanced. They can be installed more economically in the later stages of construction. Water Drives; At a number of earth fillings the steep contours of the ground rendered ordinary culvert-construction impracticable and water drives were installed. These are small-bore tunnels in solid earth or rock through- which the stream is diverted to a safe outfall away from the base of the filling. Nearly all of these are big enough to allow two or more persons of average heigbt to walk through abreast in an upright position. They vary in size from 110 square feet to 24 square feet inside cross-sectional area, and run up to 20U • yards in length. They have all been completed, the total length being 3,927ft., or roughly three-quarters of a mile. 1

Earthwork: Of the total estimated quantity of 1,371,288 cubic yards, 944,588 cubic yards, or over 68 per cent., has been completed. A large proportion of this is hard sandstone or |>apa rock. With only 32 per cent. remaining, many of the cuttings and fillings are completed or approaching completion. The most spectacular earthwork job is a short high bluff on the Waikokopu Cliffs, which ia being benched back for safety purposes to a height of 180ft. Also there are fillings of 102ft., 92ft., and 103ft. depth respectively in the central hill section. The first of these fillings is practicaily completed. The other two are commencing to rise from their broad bases. To protect the low fillings along the Waikokopu Cliffs, sections of substantiai concrete sea-wall have been found necessary. The total length required is 1,490ft. Of this, 1,100 lineal feet, or 73.7 per cent., is completed. Tunnel Construction. Tunnels: The three major tunnels are named • Waiau-Tikiwhata, Coast, and Waikoura. They are 3,278yd., 1,016yd., and 1,544yd. long respectively. There aro also teu small tunnels totalling 1,015yd. in length. The small tunnels present no outstanding problems as f'ar as can be judged at present, and they should be completed "under ordinary New Zealand methods well before the time the rails are due to be laid through them. Already one tunnel of 96£yd. has .been fully excavated and concrete-lined,

and five others, totalling 590yd. in length, have been holed through with 10ft. by 8ft. bottom headings. "The Waiau-Tikiwhata and Wai-, koura tunnels," said Mr Semple, "were of such length as to be governing factors in the progress of the whole railway-works and special consideration had to be given to the question of expediting their rate of construction. Fortunately the sandstone at both ends of each tunnel was found to be sound enough to ehable the adoption of a system new to railway tunnels in this country. This consists of the excavation of the full tunnel with the upper arched portion carried only a very short distance ahead as a working bench without any advance headings. It makes for considerably greater speed in good; ground, as the tunnellers have much more room in which to work, and explosives can be employed to greater advantage. The timbering used in 'this system is cut in segmenfcs to fit the arch, and is much lighter to handle than the' heavy bars used in the usual bottom-heading method. To obtain the maximum advantage of the full-tunnel-bench inetbod it was decided to use olectrically-operated scrapers and slides for loading tbe spoil on to trucks, which will be hauled away by electric-battery locomotives, "Three of the four faces of these" two tunnels have now been carried in under the new system for several thains, and work is proceeding so smoothly that very fast driving is indicated when the Bcraper units go into action in the near future. The fourth face, at the south.

end of Waikoura tunnel, was delayed until- a heavy approach eutting could be completed, but tunnelling is expected to start inside a few weeks." Special Pumps Used. ' He said that a further gain in the rato of tunnelling was confidently expected as far as the concrete lining was concerned. Special pumps had been 1 imported .which would pump the concrete directly into place in the fOotings, , walls, and arches at a very much faster rate than it could be placed by the old laborious hand-ahovelling process, or even by . the compressed-air-qperated concrete-gun method employed in the Tawa Flat tunnels. The 46ch. Coast tunnel situated between the two longer ones • passes through some weaker rock formations. For that reason, and also because all posfiible spoil was needed for a filling at one end, a 10ft. by ,8ft. bottom heading was being driven right through. .Alieady. 16eh, had been driven, aud the whole tunnel should be completed by the more conservative method before schedule date. "Altogether there are twcntv-two bridges to be built," said the Minister. "Work has been much impeded by the scarcity of steel. Only two are of more than medium dimensions. One is a crossing of the Kopuawhara Stream, seven miles from Waikokopu, which .is 500ft. long and 125ft. high. So uncertain is the position regarding steelsupplies that the adoption of a rein-forced-concrete-arch, jdesign, is being

seriously considered in place o± the original all-steel-viaduet proposal. "The other major structure is the Waipaoa Eiver bridge five miles from Gisborne. This consists of .steel spans on reinforced-concrete pile piers, the total length being 720ft. Good progresa has been made with the pier-construei tion, over 60 per cent. of the pile-i driving being finished, as well as onetliird of the piers. Steel for the spans, however, is an uncertain factor nera also, and it is possible that completion of the bridge structure will be held up pending its arrival. A notable feature in connection with this bridge is the use for the first time in New Zealand of a tetrahedral concrete-block apron for protecting one of the river-banka from erosion. As far as can be judged from the moderate flood tests to which it has been subjected so far, it is giving highly successful results," The Minister concluded by saying that the laying of permanent rails had' been commenced on a small scale from Gisborne in order to provide access to a! storage-site for bulk materials at Mata« whero station yard situated thxee miles out. Platelaying, however, would not be( able to advance very far from Gisborne until completion of the Waipaoa Eiver: bridge in the early part of next year* Similarly at the Waikokopu end nonj arrival of steel for bridges threatened cventually to delay platelaying^ but that would -not in any case he put in hand for about six months, pending" completion and consolidation of earth,* work on Jthe .Waikokopu gluffa