STEEL DELAYS

Gisborne Herald, Volume LXVII, Issue 20257, 27 May 1940, Page 5

STEEL DELAYS

EAST COAST RAILWAY BRIDGING PROBLEMS PROGRESS IN TUNNELS LAYING PERMANENT WAY Schedules of progress on the East Coast trunk railway between W(aikokopu and Gisborne have had to be re-cast to some extent owing to a shortage of steel on Ihe job, the shortage applying both to bar steel for reinforcement of concrete structures, and of girder steel for bridge spans. Largely through delays in deliveries of steel, it now seems likely that the completion of tlm railway to Gisborne will be delaved until well into 1941. General <p,rtCgress on the job has been excelljjjlgQtherwi.se, and a pressman who vjWS@|£l the southern portion of the construction works recently found ample evidence of the interest concentrated m the line by the Public Works Department. \ point of particular interest is that the permanent way Pas been laid as far as No. 2 Camp in the Kopuawhara Valley, and- that already works trains are dumping materials at that point for the heavier oncreling jobs, such as bridges and tunnels. Of a total distance of 35 miles of permanent way, to be laid between Waikokopu and Gisborne, approximately 20 miles has been laid to date. The greater portion of this is at the Gisborne end, where, between the Northcote road junction and Muriwai, there is a long stretch with only one major construction item, this being the Waipaoa River bridge. Between the old railhead at Waikokopu and No. 2 Camp in the Kopuawhara Valley, on the other hand, there are three substantial bridges, though none of them is comparable with the Waipaoa structure for size; and also a good deal of heavy formation. Strength Against Flooding Except for some minor jobs such as the installation of station facilities, . the construction of the line for five and a half miles north of Waikokopu can be regarded as complete, even to the laying-out of a passing-place a short distance below No. 2 Camp. Bridging jobs on this portion of the line comprise those at the Waikokopu inlet and the Opoutama lagoon, of 120 ft and 130 ft respectively, and the Kopuawhara Stream bridge at the lower end of the valley, this being 210 ft in length. In the cases of the two first-mentioned bridges, long fillings extend from each, and the spans on which the railway is carried are regarded as necessary only for drainage purposes. The Kopuawhara Stream bridge, and others further up the valley, on the other hand, are expected to withstand the onslaught ol heavy floods, and their abutments are solidly grounded on both banks. The construction of large bins for sand and shingle at No. 2 Camp is a new feature of the work now proceeding, and these bins will provide stocks of material for concreting on a number of major jobs now in hand. Their capacity is ample for the purpose. and the construction of the bins and the employment of rail haulage will cut costs materially. High-Level Bridge Construction Above this point, in the Kopuawhara Valley, the main features apart from the Tikiwhata-Waiau tunnel are two large bridging jobs, one of which will provide a magnificent example of a parabolic arch, while the other will rest on main piers sunk deep in the bed of the Kopuawhara Stream. The importance of these two high-level bridges in the general scheme of construction is substantial, lor their locations are at points where the full force of floods in the river is concentrated, and the two forms of design have been adapted to meet the particular problems raised at the respective sites. Work in the tunnels in the Kopuawhara Valley is nearly complete, several small tunnels having been completed, while others are receiving the finishing touches. The biggest shaft on the line, which connects the Waiau and Tikiwtata valleys, also is showing really good - progress, though recently there has been a good deal of trouble caused by bad ground, and a consequent slowing-down of the average rate of.progress.

An inspection of the work in the big tunnel, from the southern portal, was carried out last week by Mr. W. L. Bell, engineer in charge of construction, and Mr. Mclnnes, assistant engineer at Kopuawhara. The face has been advanced three-quarters of a mile into the hill, and is now in good ground again, with only 20 chains to go before work from the southern portal is complete. On the Tikiwhata side, progress is almost at the same stage, and the tunnelling gangs working from that end also have about 20 chains to work through to meet the men working on the southern face. The total length of the tunnel is 149 chains, and it can be claimed that five-sevenths of the major work on the line has been carried through. Specialised Tunnelling’ Work The recent difficulties encountered at the southern face were illustrated to the Herald’s representative yesterday by the steps taken to control broken rock which threatened trouble. Where tunnelling proceeds in solid rock, there is little trouble in timbering and lining, but broken rock, with a tendency to move, must be stabilised by close timbering and lined ns quickly as possible. In the Tikiwhata shaft, lateral pressure in the troublesome spot has been met by an adaptation of the timbering system, which involves the use of an additional segment in the formation of the arch, increasing the strength of the whole structure. This process lias given satisfactory results, and the main difficulty now faced is the necessity of interrupting the normal routine of applying the concrete lining in order to deal with thc*se troublespots. Elsewhere on the route, from Tikiwhata northward, tunnelling work has been up to schedule. The Waikoura tunnel is coirmlete from end to end of Its 73 chains' length, and is now being Used in the transport, of workmen and materials for jobs on the Coast section. The Coast tunnel, of 46 chains, is still absorbing attention, the bottom heading having been driven through the full length, and the breaking-down of the top heading being now in progress. It is expected that November will see this tunnel completed and lined. Some small works in the Tikiwhata Valiev are being carried on slowly, as opportunity offers, there being no urgency in respect of these tunnels.