Inquiry Told Of Earlier Kaimai Tunnel Cave-in

Press, Volume CX, Issue 32306, 26 May 1970, Page 26

Inquiry Told Of Earlier Kaimai Tunnel Cave-in

(New Zealand Press Association) HAMILTON, May 25. An inspection engineer told the Kaimai Tunnel inquiry this afternoon that there had been a partial cave-in in the tunnel in March, 1969. John Francis Briggs said the cave-in had been attributed by the tunnel manager, Mr Suitor, to the incorrect placing of vertical supports.

“I accepted his explanation, but I noticed that a depression had appeared near the centre heading,” Mr Briggs told the inquiry.

He said that after this incident additional sets were placed in position, and the surface of the batter reinforced, but by the end of March it became apparent that the pressure above the portal was pushing out the sets.

Additional buttressing of the face was undertaken, with heavy steel columns, encased in substantial concrete foundations, being placed in position.

“This was done as a matter of urgency,” he said. The inquiry began in the Maori Land Court, Hamilton, today. It is before a threeman commission comprising: Mr A. W. Yortt, a retired New Plymouth magistrate, chairman; Mr K. E. Andrews, chief engineer, a major contractor of the Snowy Mountains Hydro-Electric Authority of Australia, and Mr F. J. Handcock, general manager of the Tui mine, Norpac Mining, Ltd, of Te Aroha.

Mr D. L. Tompkins is appearing for the Public Service Association for Mr J. D. Bathgate, who will take over later in the inquiry. Mr N. I. Smith is representing the New Zealand Workers’ Union. Mr V. R. Jamieson is appearing for the Mines Department

Tomorrow the commission will visit the tunnel. It will Inspect the site of the collapse at the western portal and may also visit the eastern portal approaches. Mr Briggs said that in April, | 1969, Mr McAra, the Inspector! of Mines and Quarries, had expressed dissatisfaction with; the method of tunnelling, and; had given instructions for work to stop. Matter Of Urgency “Again, arrangements were made for the tunnel sides to be concreted as a matter of urgency," Mr Briggs said. “This was carried out for the length of the original two bottom drives.” In reply to a question from Mr Jamieson, Mr Briggs admitted the reason for Mr MeAra suspending work was that some of the wooden sets in the tunnel were cracking and bending. “On inspection we found some of the beams rather brittle, and these were replaced with stronger timbers,” Mr Briggs said. Timber used in the tunnel had come from the railway yards at Waharoa and had been mainly oak and blackwood. “It stood up to laboratory tests, but obviously there must have been weaker timber in the group than that which we tested,” he said.

Questioned 6y Mr Yortt, on the responsibility for faulty material on the project, Mr Briggs said: “I would regard myself as morally responsible, but I think the department (Works), would hold both the resident engineer and myself responsible.” The tunnel overseer, Hugh A. Neely, said he believed his work-mates who were killed in the collapse would have been saved if a conventional concrete shell had been used.

“If conventional concreting had been brought up behind us everything would have been saved, and I don’t think any lives would have been lost,” Mr Neely, one of the seven survivors, said. Under cross-examination by Mr Smith, Mr Neely said it was his belief that in most tunnelling operations concrete shells were kept well up to the workmen and provided some form of shelter in an emergency. “At the Kaimai tunnel there was just nowhere for the men to run,” he said. “A concrete shell would have provided them with a haven of safety to run into.” Enormous Pressure Mr Neely said he had seen many runs but never anything like the Kaimai collapse. “There seemed to be enormous pressure being exerted from the outside on to the tunnel,” he said. “When I ran to warn the others it was just trickling and crumbling. It had started to disintegrate, and was ready to go.”

Asked by Mr Smith what ihe thought of the safety of ithe tunnel, Mr Neely said he ! thought tunnelling operations used were unconventional. ‘The way the tunnel was 'worked was unlike any other procedure I have seen used in New Zealand,” he said. Asked by Mr Smith to enlarge on this statement, he said the normal method of tunnelling was to remove the soft earth and go straight to the hard rock. “In this case there was no hard rock left,” he said. “I have had no experience of the Kaimai method of tunnelling back out towards the portal, and I think this is dangerous because the soil is loosened. It would have been much less dangerous if we had been working inwards at the time.”

Outlining his actions just before the collapse, Mr Neely said that when it appeared obvious the tunnel was caving in he had called to the others to run. Water Increasing - “If they had run then I think they would have got out of it without much trouble,” he said. Everything appeared to be

in order when he took over shift at 8 a.m. on the day of the collapse, he said. Work was being carried on in the top heading, which was giving more concern than the portal because they were not sure what was ahead and water was increasing. Part of the shift was working in the heading and the rest were working back towards the portal, bringing the tunnel up to the required height for concreting. Mr Neely said he had just returned to the office from the tunnel when one of the men called to say Jim'Smart (killed in the collapse) wanted to see him. He spoke to Smart, then someone else called out and he got inside the tunnel as soon as he could. “I had one look at the 3ft face where the head laths were,” Mr Neely said. “The face seemed to be crumbling as if an enormous weight was pushing on it. I could see there was no chance in the world of holding it. “It then crossed my mind that I would have to warn the rest of the shift working in the face of the danger. So I told Smart and the men with him to get to hell out of it “I then took off towards the face and called out to the shift boss. I did not realise at the time that they were in the safest part of the tunnel. “I started back again towards the portal. I got part way in the steel rings and the whole place came down with a roar.

“I remember flying through the air and then boulders and timber falling on me. I wondered then if it would stop before I was buried right over. It did and I was well held. Shield Method Barry John Butcher, resident engineer at Otahuhu for the Ministry of Works, told the inquiry: “I can see now perhaps we should have used the shield method in the tunnel. But I say so with hindsight, since the disaster.” Mr Butcher took over planning and preparatory work for construction of the tunnel in 1968 on a part-time basis.

He said the short length of about 1000 feet of tunnel, the loose formation of the soil, and the cost were all factors which counted against the method. [Under the shield method a large steel tube, in which men can work, is driven into the soil.] Mr Butcher said it had been decided after consideration to use a three-drive method, which involved one drive from the top and one down each side. This method was well proven in difficult conditions, be said. It was the method used for planning. Methods would always be varied to meet ground conditions as they were encountered. It was planned to keep arched concrete always close to excavations, then take out the core of the tunnel. Difficult, Wet Questioned by Mr Yortt, Mr Butcher agreed the Ministry of Works must accept overall responsibility for the tunnel. *

Bruce William Spooner, chief civil engineer for the Ministry of Works, said the

approaches to the rock for the first few hundred feet were tunnelled out of difficult, wet country. About 50 feet in from the portal it became obvious that the steel supports were having trouble taking the weight and were progressively sinking lower. At that point heading work had been sloped upwards to regain height. Mr Spooner disagreed with Mr Smith that after about 25 feet of tunnelling the Ministry of Works had gone off its original plans and used a method of trial and error.

“The ground was such that it became evident we could not continue with our original process of excavation,” he said. Mr Smith: Was consideration given to building the open cut further into the mountains than actually took place? Mr Spooner: We gave a lot to the question of where to break under. It was not particularly featured on plans to fix a portal site until the open cut went through.

He said that since the collapse the open cut had been taken about 120 feet, past the original portal. Mr Smith: On reflection, do you consider a safer method of cut and cover could have been used in the first instance? “Not Unsafe” Mr Spooner: We had no reason to believe that the tunnel should not have been started where it was.

He agreed that cost and safety were dominant factors in building the tunnel. In reply to a question from Mr Smith he said that even if the more conventional cut-and-cover method of tunnelling had been employed the tunnel would not have been any safer to work in. “I don’t believe the way we started or the methods used were unsafe for the men,” he said. “We had no written book of safety rules to hand to each man, but we work under the rules as set out in the Quarries Act. “I don’t believe any book of safety rules is as good as having experienced men supervising work in the tunnels.” Mr Spooner said the general responsibility for safety lay with every member of staff, from the project engineer down, but in the tunnel itself it was the direct responsibility of the tunnel manager. “Yes, I knew that some of the men in the tunnel were very inexperienced,” Mr Spooner said in reply to a question from Mr Smith. “But those in charge at the time of the collapse were fully experienced.” Reginald Ernest Hermans gave evidence of bores in written submissions. He said two sites for the tunnel entrance had been considered—the present one and one about 10 chain south. Mr Smith asked Mr Hermans if he had been unhappy with test bores put down by contractors.

Mr Hermans: We always endeavour to obtain a 100 per cent core recovery. For various reasons this was not possible. Naturally we were disappointed.

Flood Relief.— The New Zealand Red Cross Society yesterday sent $lOOO to floodstricken towns in Rumania.— (PA.)