TAG 166 - Geological Society of Australia

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Engineering geology advancesThe investigation years by the SMHEA commenced in about 1949 and ateam of geologists was set-up under leadership of Dan Moye as ChiefEngineering Geologist, from 1949 to 1967. He built a team thatpioneered many of the now-accepted practices in the discipline ofengineering geology, including drilling methods, rock-mass classification,rock mechanics applications, tunnel logging methods and waterpermeability testing.Dan Moye (1955) stated in his landmark paper:Engineering geology in practice is a service to civil engineering(including the civil aspects of mining engineering). The engineeringgeologist should be, first and foremost, a well-trained geologist.This statement still holds true today.During the Snowy Mountains Scheme’s site investigations, civildesigns, construction supervision and monitoring, the followingfundamental issues were addressed:l classification of weathering of granitic rocks and strengthestimationl diamond drilling — triple-tube core barrels to improve core recovery,core logging and boxing methods standardised, careful recording ofrock defectsl improvement of the water pressure test (Lugeon) method.During celebrations of ‘The Spirit of the Snowy Fifty Years On’, ProfessorET Brown stated, “… the Snowy’s geological and engineering staff wereahead of their time”.The rocks encountered in the various project areas were commonlygranitic — granites, granulite and gneiss — with variable degrees ofweathering, often to 100 m depth. It was clear that a system for assessmentof the performance of rocks and soils in slopes, foundations andunderground openings was needed. This was when a classification ofweathering was introduced by the engineering geologists, starting from‘fresh’ (unweathered) through to ‘completely weathered’. This and similarsystems, defined internationally by various institutions such as theInternational Society for Rock Mechanics, form a basis for engineeringdescription of rocks today.In addition to weathering, the definitions of engineeringproperties of soil and rock materials were expanded to cover substancestrength, geological structures, groundwater permeability and state ofstress so that predictions could be made about excavatability, foundationsuitability and stability of slopes. As the work proceeded underground,a new set of guidelines became critical for ground support (this isdiscussed later in this article).The engineering geologists also became part of the design team,with contributions to design and tendering, and then to methods ofconstruction and site supervision. During the development, contractswere awarded on a lump-sum basis, as the old government-supervisedday works contracts on large civil projects were being phased out. Thus,the tender packages required a high standard with consistent and highqualitydata. The need to provide geological information was aided bythe discipline of obtaining quality data and standardising thepresentation and rock quality classifications.ABOVE: The bucket test — bucket filledwith crushed rock and model rockbolts used to demonstrate theprinciple to tunnel workmen. Imagecourtesy SMEC collection.RIGHT: Eucumbene–Tumut tunnel,indicating construction activityin 1954. Image courtesy SMECcollection.Advances in rock-bolting technologyAt this time in the 1950s to 1960s, rock mechanics was an emergingdiscipline and development of underground rock engineering wasadvanced during construction of the Tumut 1 and 2 underground powerstations. Early stress analyses were typically done as a two-dimensionalphotoelastic modelling process. It was only after Tumut 1 was excavateddid in situ stress testing start — by the flat jack method.These studies and practical underground excavation work led tohuge advances in rock-bolting technology:l The technique of rock bolting was one of the many innovativeengineering achievements used on the scheme to prevent rockinstability.l The properties and behaviour of rock played a major role indetermining the design and construction programs adopted.l Steel bolts of differing lengths and spacing were inserted, wherethey were found to be an excellent anchorage rock in tunnels.l Grouting of bolts into the rock became the normal practice.In the words of engineer Aubrey Hosking:Previous to the Snowy, rock bolts were put up individually — this is, youput up a rock bolt because there was a bit of rock that was going to falldown, so you put a bolt up and pinned it to the rock behind. You’ve got tohave an anchoring inside, and then you tension the bolt. If you’re compressingit in the direction of the bolt, there is also a lateral force generated.What the Snowy did was to realize [sic.] that this lateral force couldmake the bolt self supporting — that is [if] you had rock bolts in a pattern,instead of individually, they could reinforce one another and create astructural entity, which would support a power station or a tunnel roof.At one stage the underground miners expressed concern aboutworking under a free span of rock with no steel rib support or otherconventional support systems. All they could see were many face platesof the supporting bolts. So a demonstration was made by the geotechnicalteam by placing aggregate in a large steel bucket, then smallmodel bolts were embedded and tensioned against inch-size face plates.The bucket was then upturned and nothing fell out. Whether thisconvinced all miners to get back underground was not recorded but formany years there was a large mine skiff with full-sized bolts hangingupturned near the Snowy Mountains Engineering Corporation (SMEC)laboratories in Cooma.TAG March 2013| 23
Tumut 2 tailwater tunnel during construction. Image courtesy SMECcollection.Tumut 2 power station cavern under construction. Image courtesySMEC collection.Field tests to assess the rock bolting were conducted at LambieGorge near Cooma and detailed design and analyses were carried from1956 to 1962.By 1959 over 40 000 bolts had been installed. This reduced the steelrequired for support to one-eighth of that for conventional methods.The resulting cost savings were about 45%, with additional benefits forsafety and rates of tunnelling.Professor Brown has also stated the development of rock boltingwas “… probably the most significant engineering development madeon the Snowy Scheme”.Guthega Dam under construction — image taken in 1954. Image courtesySMEC collection.The rock bolting during driving of tunnels allowed for a hugeimprovement in efficiency and some records in tunnelling rates oversubsequent years. The construction of major tunnels through the SnowyMountains range reached a total of 145 km with excavated dimensionall less than 7 m. They were driven mainly through granite, with somequartzite, siltstone, slate and hornfels.The longest was the Eucumbene–Snowy Tunnel at 23.5 km. It washorseshoe-shaped and had a diameter of 6.9 m. The best tunnelling ratewas in the Tooma–Tumut tunnel, where a 160-m drive was achieved ina 6-day week.Legacy of the SnowyThe legacy of the Snowy for engineering geologists has includeddisciplined rock description and classification, improved quality ofdiamond drilling and in situ testing and pioneering of methodsinformation for tenderers.In rock-bolt research, the legacy has been pioneering of patternbolting, instigating bolt grouting and improving installation procedures.The discipline of rock mechanics has benefited from developmentof in-stress measurements and rock-support analysis methods.As well as the testimony of the successful completion of the majordams, tunnels and power stations, Daniel Moye published graphicaccounts of the way geology was applied during their planning andconstruction. Most of the principles and techniques of engineeringgeology described in these accounts are still accepted and indeed arestandard practice worldwide today.ROBERT GOLDSMITHR E F E R E N C E SBrown, ET, 1999. Rock Mechanics and the Snowy Mountains Scheme. The Spirit of theSnowy — fifty years on. Australian Academy of Technological Sciences andEngineering, p 89–101.Moye, DG, 1955. ‘Engineering geology for the Snowy Mountains Scheme’. Journal ofthe Institute of Engineers Australia 27: 287–298.McHugh, S, 1989. The Snowy — the people behind the power. William Heinemann,Australia.Mills, W, 2005. ‘…the most significant engineering development made on the Snowyscheme’. Newsletter of Engineering Heritage, Australia.24 |TAG March 2013
Page 3 and 4: From the PresidentWelcome back from
Page 5 and 6: Society UpdateGovernance changesCom
Page 9 and 10: Society UpdateFrom the AJES Hon Edi
Page 11 and 12: Society UpdateEducation&OutreachIn
Page 13 and 14: A conference in 2014 is envisaged a
Page 15 and 16: NEWSIn the news this issuen NRG Roc
Page 17 and 18: It is proposed that an important el
Page 19 and 20: IGCP projects with Australian leade
Page 21 and 22: Ediacaran Golden Spike localityVisi
Page 23: Feature 1Feature 1Snowy Mountains H
Page 31 and 32: Fossil hunting organised by Kronosa
Page 33 and 34: Fortunately for Paul Stumkat, he is
Page 35 and 36: Year 12 EES students from across WA
Page 37 and 38: Special Report 3Global warming and
Page 39 and 40: As indicated in the table accompany
Page 41 and 42: Ian Percival spoke on protecting an
Page 43 and 44: Books for reviewPlease contact the
Page 45 and 46: An introductory paper to the volume
Page 47 and 48: this land, and showing the richness
Page 49 and 50: Geology of QueenslandP Jell (Ed)Dep
Page 51 and 52: O B I T U A R I E SSylvia Whitehead
Page 53: The Australian GeologistBackground

TAG 166 - Geological Society of Australia

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