Surveying at Oyu Tolgoi Copper/Gold Mine - Chris Hutchison - AIMS

SURVEYING AT OYU TOLGOI 

COPPER/GOLD MINE 

MONGOLIA 

March/April 2010 

AIMS NATIONAL CONFERENCE ‐ CAIRNS 

8‐10 August 2012 

Chris Hutchison FAIMS, MIS 

Registered Surveyor

OWNERSHIP & HISTORY 

• Copper has been recovered from this 

area since the bronze age as indicated 

d 

from the existence of small circular 

pits and minor copper smelting slag. 

• This site was discovered by Ivanhoe 

Mines (a Canadian Company with 

worldwide interests) and verified by 

drilling over the last 10 years. 

• In October 2006, Ivanhoe Mines and Rio Tinto signed a long term 

investment agreement with the Mongolian Government for the 

construction and operation of the Oyu Tolgoi copper‐gold mining 

complex. In March 2010, the Mongolian Government announced 

that conditions i precedent had hdbeen satisfied ifidand that the 

agreement now has full legal effect.

OWNERSHIP & HISTORY (cont) 

• The Investment Agreement created a Partnership: 

‐ Ivanhoe Mines 66% 

‐ Mongolian Government 34% 

• Rio Tinto joined Ivanhoe Mines as a strategic 29.6% 

interest partner in the venture in 2006. 

• Based on drilling results, there are verified estimates that 

the Oyu Tolgoi resource contains 81 billion pounds of 

copper and 46 million ounces of gold.

OWNERSHIP & HISTORY (cont) 

• Development is ahead of schedule for initial production 

to commence later this year with the start of commercial 

production in 2013. 

• A 100,000000 tonnes of ore per day copper concentrator will 

process the initial open pit operation. 

• This paper refers to survey work associated with an 

85,000 tonnes per day underground block‐cave mining 

operation being developed at the Hugo Dummet North 

Deposit with initial production in 2015. Lateral 

development on the 1300 metre level at Hugo North is 

ahead of schedule.

GEOLOGY 

The South Gobi area 

lies near the boundary 

of the South 

Mongolian and the 

South Gobi tectonic 

units. 

It has been 

increasingly arid since 

the late Cretaceous 

period and has been 

subject to continental 

uplift since the early 

Mesozoic period.

GEOLOGY (cont) 

The Oyu Tolgoi property, in general, has sparse outcrops comprising 

less than 20% of the area. Mineralisation at the site is characterised 

by multiple copper gold porphyry centres which occur above and 

partially telescoped onto the underlying Cu‐Au porphyry systems. 

Hugo Dummet North is almost 

entirely within basalt. 

Molybdenite occurs locally in all 

rock types. Gold (ppm):Copper 

(%) ratios over much of the 

deposit are 110b 1:10 but, in strongly 

quartz‐veined intrusions, the 

ratios increase to 1:1.

SITE CONDITIONS 

Temperature at 

the mine varied 

from +10°C 

to ‐20°C during 

March 2010 while 

we were on site.

SITE CONDITIONS (cont) 

Accommodation at the site was in a camp and most of it is in “Girs”. 

These are the felt 

tent‐like houses used 

by the Mongolian 

nomadic people. 

We were 

accommodated in 

a twin room with 

shower/toilet 

facilities in the 

building similar to 

many Australian 

mine sites.


Transport to the mine from 

Ulaanbaatar was by a 90 seat 

aircraft chartered by the 

mine which operates into and 

out of the mine four days per 

week. 

Heavy equipment is brought 

to the site by overland 

transport through the desert. 

There are no formed roads or 

railways between the mine 

and Ulaanbaatar. 

The mine site is only 90 km from the Chinese border and there are 

likely to be connections made to Chinese infrastructure.


The mine lies in the South Gobi Desert which is an extension of the Tibetan Plateau. 

The site is at 1280 metres above sea level. 

It is in UTM Zone 48 

and the site 

coordinates are WGS84 

which makes them, in 

practical terms, the 

same as our MGA but 

in Zone 48.


Mongolia has a population 

of about 4 – 5 million. 

About 1 million live in the 

capital, Ulaanbaatar, there 

are another 4 or 5 regional 

cities and the remainder of 

the population live the 

nomadic rural life that is 

centuries old. 

There are no rural fences. All appears to be “common” land where stock (horses, 

pp ( , 

sheep, goats and camels) are grazed. There must be farms of some sort as trucks 

bring vegetables into Ulaanbataar daily but I didn’t see any farms.

PROJECT REQUIREMENTS 

AND PROJECT TEAM 

• Redpath, a Canadian company, has been contracted to construct the shafts 

and underground development at the Hugo North mine. 

• C R Hutchison & Co Pty Ltd had provided 

gyro orientation services and technical 

support to CEH Dapto during the 

completion of a survey contract on the 

Big Gossan Project at the Freeport Mine 

in Indonesia a few years ago for Redpath. 

The success of that project encouraged 

Redpath to contact Matthew Smith of 

CEH Dapto in Wll Wollongong with a view to 

engaging him on a similar project in 

Mongolia. Matthew contacted C R 

Hutchison & Co with a request for gyro 

and specialised equipment support for 

the project. 

• The Australian team for this project 

was Team Leader Matthew Smith of 

CEH Dapto and Chris Hutchison (who 

couldn’t resist the opportunity).


AND PROJECT TEAM (cont) 

• The project required that we: 

‐ Transfer survey 

control from the 

surface network to 

the shaft collar and 

the centre of a raise 

bore site which was 

proposed to be drilled 

from the surface to 

the 512 level;


AND PROJECT TEAM (cont) 

‐ Transfer survey control via the single existing shaft to the 512 level, establish 

orientation at that level, traverse to the design location of the raise bore at that 

level and establish control there for a raise bore from 512 level to the 1300 level; 

‐ Transfer survey control via the 

shaft to the bottom of the mine 

at the 1300 level, establish 

orientation at that level, 

traverse control to the raise 

bore chamber on that level and 

extend survey control by gyro 

supported traverse throughout 

the 1300 level workings; and 

‐ Report the results of this work.

TECHNICAL SOLUTIONS 

• Due to the isolated area of the mine, it 

was decided dto use our GAK1 gyro 

attachment to our T2 theodolite for gyro 

orientation work rather than risk sending 

one of our Gyromats unaccompanied to 

Mongolia and back. 

The GAK1 was carried in hand luggage all 

the way to protect it. It did create a lot 

of interest at customs X‐ray check points 

and a copy of its handbook was essential 

to convince security that it was really a 

piece of surveying equipment. 

• Our TCRP1201 total station was taken 

and, together with Leica precise prisms, 

used for traverse work on the surface 

and underground.

TECHNICAL SOLUTIONS (cont) 

• Laser plumbing equipment, umbrellas (also caused some interest in 

customs), the trusty HP41CV calculator, diagonal eye pieces (for 

sighting shaft plumbing piano wires), laptop computers and other 

small items were all taken as passenger’s luggage (which included a lot 

of cold weather gear, some from Antarctic days) and made the 

combined luggage of the team 100 kg overweight from the Air China 

point of view. 

It made me very thankful that Matthew Smith is a very fit and strong 

It made me very thankful that Matthew Smith is a very fit and strong 

young man when it came to moving this gear through security for 

various air transport movements.


• A German team had been at Oyu Tolgoi in 2007 to transfer control down 

the #1 shaft at Hugo North. They used a DMT Gyromat (early model) to 

establish orientation and some 8 wall stations at the 1300 level with 3D 

coordinates. 

They plumbed the shaft using optical plumbing from the surface with 

verification by measurement of horizontal and vertical angles and slope 

distances from the foot of the shaft to stations at the shaft collar using a 

high precision total station. 

However, due to the temperature gradient in the shaft of about 40 

degrees Celsius, the effects of refraction reduced the precision of the 

plumbing so that the German group reported that the accuracy of their 

results was not better than plus or minus 100 mm. Our hope was to 

achieve a tighter coordinate solution as it was a requirement that the 

two raise bores became a single vertical shaft from the surface to the 

1300 level.


• As the mine is relatively new, we enquired by email if any of the piano 

wires used to sink the shaft still existed and we were told that three of 

the original six remained. 

The team resolved to go back to the “tried and true” old fashioned 

method of plumbing the shaft using those wires. They were thoroughly 

checked to ensure they were not fouled on any part of the shaft 

concrete and all the steady brackets were fully opened to ensure the 

wires followed gravity without a bend. 

Prior to commencement, 100 pound weights were attached to each 

wire and each weight was damped in a 44 gallon drum filled with oil. 

The ventilation was shut down for 12 hours before measurement so 

that the wires could steady.


• Rather than observe Weisbach triangles at 

the 512 and 1300 levels from the wires into 

each drive, it was decided to “radiate” each 

of the three wires using the gyro orientation 

bearing so that there were three 

independent coordinates available for the 

initial station at each level. 

The wires were carefully observed a 

number of times at each level (using the 

diagonal eye piece at 1300 level because of 

cage infrastructure) and we were surprised 

to find them very stable with ihno long period 

oscillation discerned. Distances to the wires 

were measured reflectorless with a backing 

sheet held behind the wire to assist where 

possible.


• Gyro orientations were measured at the shaft at 512 and 1300 levels as 

well as at the raise bore chamber (512 level) and at the furthest inbye 

traverse leg (1300 level). 

At the surface, a comparison 

gyro orientation was 

measured between two 

survey control pillars (which 

provided a rotation for the 

other orientations) and 

another gyro orientation was 

measured on a baseline 

straddling the surface raise 

bore position to “close” the 

surface traverse angles at 

that site.


• Connections were made from the 

surface traverse to the #1 shaft 

subcollar area and at that level to the 

top of the three piano wires to 

determine their coordinates which 

were transferred to the lower levels. 

• The underground traversing was 

completed using the TCRP1201 

and precise prisms using “sets of 

angles” software.

CONCLUSION 

• The coordinate transfer from the surface to the 512 level by three wires showed 

a standard deviation of plus or minus 5 mm, a surprisingly good result. 

The coordinate 

transferred from the 

surface to the 1300 level 

by three wires showed a 

standard deviation of 

plus or minus 10 mm, an 

equally surprisingly good 

result.

CONCLUSION (cont) 

• Our GAK1 gyro was calibrated at Newcastle University baseline 

just prior to departure for Mongolia. 

The comparison between our GAK1 and the datum line of 

orientation adopted for the project (baseline joining OT13 and 

OT11 surface pillars) was GAK1 plus 31.6 arc seconds equals 

datum. This rotation of +31.6 arc seconds was applied to all 

other gyro orientations to maintain their relativity to the surface 

datum line. 

At the surface raise bore baseline, the initial gyro comparison 

showed that the coordinate join by the mine coordinates differed 

by 36 arc seconds (higher) h than the gyro bearing. 

At the 512 level, the mine coordinate join at the shaft differed by 

7 minutes 36 seconds (higher) than the gyro bearing and 2 

minutes 44 seconds (higher) than the gyro bearing at the raise 

bore chamber.


At the 1300 level, the mine coordinate join near the shaft differed by 6 seconds 

(higher) than the gyro bearing. This shows a good comparison between the German 

gyro controlled coordinates of the wall stations at that level. 

The angular misclose in our traverse at 1300 level compared to the initial gyro showed 

only 11 arc seconds and, at the 512 level, the difference between the gyro 

orientations was 4 arc seconds. After adjustment of our traverse for the angular 

miscloses revealed by the gyro orientations and using the coordinates we transferred 

to the surface and into the mine, the new coordinate joins differed from the gyro 

bearing as follows: 

‐ Surface calibration baseline coordinate grid ±0.0 seconds to gyro (datum line) 

‐ Surface raise bore baseline coordinate grid ‐0.2 seconds equals gyro 

‐ 512 level (shaft) coordinate grid +1.4 arc seconds equals gyro 

‐ 512 level (raise bore) coordinate grid +1.0 arc seconds equals gyro 

‐ 1300 level (shaft) coordinate grid ‐0.7arc seconds equals gyro 

‐ 1300 level (inbye traverse end) coordinate grid +0.3 arc seconds equals gyro


The raise bore positions at surface, 512 level and 1300 level are affected by the 

combined projection and height scale factors at their levels. The projection scale 

factor is a constant but, because of the mine location in the zone and the latitude of 

the mine, the height scale factor varied by about 200 mm per kilometre between the 

surface and the 1300 level. 

This fact is further complicated by the local Mine Surveyors not using either a 

projection or height scale factor in their traverses and the principal’s requirements 

that we provide plane rectangular (mine grid) coordinates for survey stations 

(including the raise bore sites) at each level. 

This led to there being a different local coordinate at each mine level for the raise 

bore site to maintain a truly vertical shaft hftowards the centre of the earth.


There were, as a result, some time 

consuming calculations (and check 

calculations) to finally provide the 

requested coordinates. 

However, we were very pleased to 

have the principle of our work 

proven in August 2010 when we 

received an email from Mongolia 

advising that the drill hole from 

the surface to the 512 level broke 

through “spot on” our prediction. 

As we have not received any further information it is believed they 

are still working on the 512 to 1300 level and we are hoping for a 

similar result.

Acknowledgements 

• Thanks are due to Matthew Smith and CEH Dapto for 

giving me the opportunity to take part in this interesting 

project. 

• Thanks are also due to Paul Beveridge, the new owner 

of C R Hutchison & Co Pty Ltd, for his positive attitude 

to the project and his trust that the special surveying 

equipment would be returned to Australia safe and 

sound. 

• Thanks to Nigel Atkinson, Nicholas Baillieu and the 

committee organising this conference for the 

opportunity to talk about this project. 

Chris Hutchison FAIMS, MIS 

Registered Surveyor

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Surveying at Oyu Tolgoi Copper/Gold Mine - Chris Hutchison - AIMS

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