The coal mining industry depended on a wide range of skills and occupations for the design and management of its operations. One of those professional skills which is far less well-known than it deserves is that of the mine surveyor, guiding and documenting underground mining operations, in an industry where operations underground often came within metres of each other. From their knowledge and experience of this central work, Andy Hubscher and John Coll have provided the article which follows.
The mine surveyor is required to conduct surveys, prepare plans and securely maintain survey data to the standards required by current legislation. The technical support provided by the surveyor is critical to the design, planning, day to day operation and safety of surface and underground mining activities
The basic principles of mine surveying have not changed throughout history, but the development of instruments and data management has been revolutionary.
Surveying in mines has existed for as long as tunnels and shafts were driven to mine seams of coal. Early methods involved the use of chains or measuring tapes and the “Miners Dial” which was a magnetic compass set upon a tripod. Headings (tunnels) and cut throughs (joining sets of headings) had to be driven to a plan set by the manager of the mine. Early mining layouts where haphazardly driven with only the main rope haulage tunnels required to be reasonably straight. Other tunnels were driven to the conditions that existed, mainly geological which include roll stones, igneous intrusions, roof rolls, dip of the seam, cleat of the coal and faults.
With the introduction of mining machinery the layout of the mine consisting of these headings and cut throughs had to be more accurately laid out by the mine surveyor. Direction control was achieved by “line of sight” through the survey stations. This was later achieved by the use of the theodolite to keep the headings and cut throughs on a pre-planned direction and to measure angles accurately as required. Up until the 1950s theodolites were of the Vernier type to measure angles. These were superseded by the introduction of the Microptic theodolites, giving a higher accuracy of angle readings.
(1) Telescope, (2) Vertical Circle, (3) Spirit Level, (4) Vertical Standards, (5) Horizontal Circle, (6) Bottom Clamp, (7) Levelling Head Screws, (8) Top Clamp, (9) Horizontal Axis, (10) Slow Motion Tangent Screw, (11) Reading Microscopes, (12) Vernier Clamp, (13) Slow Motion or Tangent Screw, (14) Centring Device, (15) Spirit Level
In the 1980s lasers were introduced and set up on survey sights for machine guidance. The Laser Plummet is now also used for vertical alignment in shafts, replacing the plum bob.
It was also required to establish a level datum in a mine, to enable contours to be drawn for the mine workings on the various mine plans. The level and staff were used for this purpose.
Calculations to enable workings to be plotted on the particular plan were computed using seven figure logarithms to obtain the co-ordinates for survey stations in and on the surface of the mine. Logarithms were a slow and arduous method of calculating co-ordinates for established survey stations.
Survey field books, calculations and plans were “Hard Copy”. Plans were initially hand drafted on paper and special linen using Indian ink and quill pens. The next advance was the development of stable drafting film, isograph pens and stencils for lettering. Plans on drafting film could be easily reproduced onto light sensitive paper and carefully edited.
The digital revolution began for the surveying profession began in the late 1960s when the “Scientific Calculator” was introduced, greatly improving the speed with which calculation were carried out.
In the “field” advances that followed included Electronic Distance Measuring (EDM) devices using reflective prisms in conjunction the theodolite. Then came digital levels, electronic theodolites and total station instruments with built in computers, lasers, robotics, reflectorless (EDM) measuring, scanning ability, 3-dimensional (3D) data storage and download capabilities.
Surface surveying also uses Global Positioning System GPS) based on satellite signals to position survey stations. Drones and laser scanners with appropriate software are used to carry out detail surveys particularly in inaccessible locations. All these advances in the “field”, when used by competent operators, have greatly improved accuracy and data collection.
In the “office”, computers both mainframe and “desktop” had arrived. Software programmes were developed for data processing including routine survey calculation, control survey adjustment and drafting. Computer Aided Drafting (CAD) had taken over from hand drawn plans. This was the birth of “Soft Copy” digital plans which are Portable Digital Format (PDF). Field notes are also created in the total station and stored digitally.
Field work is now carefully downloaded from the instrument and automatically represented in 3D by the appropriate CAD software. The survey can strategically edit the digital plan and attach additional spatial data such as dates of mining and extraction.
The mine surveyor’s skill set has to expand to keep pace with the evolving technical advances while adhering to the basic principles of surveying and the constantly changing legislation..
The Mining Surveyor (NSW)
At the time of writing, the duties of the mining surveyor are strictly regulated by:-
- Work Health and Safety in Coal Mines and Petroleum Sites) Regulation 2014
- Survey and Spatial Information Regulation 2017
- Survey and Drafting Directions for Mining Surveyors 2020 (NSW Mines)
- Australian Standard for Mine Plans – Preparation and Symbols (AS-2916 ) 2007
The mine surveyor must at present have university degree qualifications and complete the Board of Surveying and Spatial Information (BOSSI) examination. Prior to this, the Mines Department of NSW, now renamed The Department of Primary Industry and Investment, set the Mine Surveyor’s Certificate of Competency examination two times a year. The examination consisted of two surveying computation papers and a mine plan drawing paper. Upon passing these examinations, the candidate had to then participate in a practical survey and oral examination. Evidence of practical experience and the completion of a TAFE (Technical and Further Education) Mine Surveyors Certificate Course was also required, with a minimum age of 21 being a prerequisite prior to being appointed as a Mine Surveyor.
In addition to surveying subjects at TAFE, basic geology, mining practices and legislation were also part of the certificate course.
The Nominated Mine Surveyor is appointed at the mine by the colliery Mine Manager.
Underground Mine Surveying
Origin of Coordinates
Probably the most important function to setting up a mine from the surveyors perspective, is to establish a highly accurate baseline and height datum on the site, to be included in the State Survey Control Network. The current coordinate system and height datum for surveys and plans must be Map Grid of Australia 2020 (MGA2020) and Australian Height Datum (AHD71). The baseline must be well protected from possible movement by outside sources and ground movement from mine subsidence. The transfer of a baseline from the surface to the underground workings at a mine, with only shaft access or shaft and drift mine access, is extra challenging.
Secondary and Subsidiary Surveys
These are surveys carried out to allow the mining process to advance into the seam with headings and cut-throughs being driven to predetermined dimensions. Lasers are now used and provide a highly accurate method of keeping “on line”. Surveys to determine the levels of each intersection are carried out with the total station during routine advancement of survey stations to determine dip and seam floor contours. The contours are generated by software programmes.
These surveys are substantially marked, closed on the survey network and completed to the prescribed accuracy. Some longwall mines experience significant horizontal roof movement, it therefore prudent to re-survey these suspect areas after mining has passed.
Maintenance of survey equipment: Survey equipment must be maintained, kept in good adjustment and calibrated annually against an approved baseline. The surveyor must ensure Electronic Survey Equipment is “fit for purpose”, approved and inspected for use in hazardous environments.
Specific Survey Requirements
Most modern mining operations require the Mine Surveyor to provide Geospatial Data as stated below.
- Plans required under the Work Health and Safety (Mines and Petroleum Sites) Regulation 2014
- The Mine Surveyor has roles and responsibilities under the Safety Management System designed to control critical processes and manage hazards identified and adapted for the particular mine.
Mine Management Plans cover: – Emergency Response, Fire and Explosion, Evacuation, Inrush, Ventilation, Outburst, Gas Monitoring, Strata Control, Connecting Workings, Conveyor Belts, Transport, Hazardous Substances, Refuse Emplacement, Wastewater and Pumping
- The Mine Surveyor must submit the Mine Survey Plan Soft Copy in PDF format & Mine Working Digital Spatial Information in data files, and Declaration of Certification to the NSW Resources Regulator at 12 monthly intervals and at cessation of workings. These submissions are uploaded electronically through NSW Resources Regulator Portal.
- Operational Plans
The mine surveyor is crucial to the day to day running of the mine providing spatial data and for:-
- For Short and Long Term Planning Conferences;
- Provide plans which show driving sequences and auxiliary ventilation, geological information etc.
- For Longwall Operations;
- Plans showing seam thicknesses, contours, geological information.
- Positioning installation of machinery
- Reference marking for face position
- Positioning marks for longwall removal
- Plans showing outburst information
- Outburst Management for Development Drivages
- Plans showing drilling patterns for each section of the mine
- Plan showing changes in mining methods.
- Plan showing geology
- Plans showing insitu gas content and composition samples
- Plans showing zones of authorised for mining
- Special Projects
- Layout and survey information for stone excavation of bins, drifts, shafts and staple shafts.
- Survey information for underground excavations, such as conveyor belt installations.
- Set Out for the accurate positioning of machinery and plant.
The following are typical of the mine surveyor’s miscellaneous duties:-
- Ensure a safe working environment for his area of responsibility
- Report and rectify if possible any risks to safety observed in the workplace
- Provide technical support to the mining and engineering staff
- Participate in Risk Assessments to identify hazards, evaluate the risks and determinate ways to eliminate or control them.
- Provide induction, education and training to enhance the technical skills of trainees. Monitor their level of competency.
- Set standards and keep abreast of new technology.
- Maintain good external relationships with government departments, consultants, contractors and neighbouring colliery surveyors and staff.
- Set and control the survey department’s budget.
- Maintain and update the survey office computer’s hardware and software.
The future mine working layout is mostly determined by the mine manager, assisted by the planning manager, ventilation officer, geologist, gas drainage coordinator, surveyor, and environmental specialist.
The following geospatial data has to be considered when laying out a mine
- Size of the lease area and position of entries
- Adjacent colliery workings – abandoned, operating or proposed to ensure the prevention of inundations of gas or water.
- Depth of cover. Depth, aquifers, other seams, strata. Depth of cover also determines pillar dimensions. This information is gotten from borehole information
- Seam thickness. Determines machinery type to be installed
- Multiple seams. Order of extraction of seams and effects this will have on future operations
- Dip of the seam.
- Virgin seam gas composition and content.
- Geological features. Dykes, volcanic activity, faults, disturbed zones
- Surface features. Dams, creeks, ocean bodies, swamps, lakes, flood zones, catchment areas, cliff lines
- Surface infrastructures. Roads and tunnels, railways and tunnels, gas and water pipelines, water tunnels, overhead power lines, urban areas
- Subsidence effects
- Mining legislation
All of the above involve the participation of the Mine Surveyor. Plans have to be drawn, surveys made, infrastructure has to be positioned.
Compiled by Andy Hubscher and John Coll. 2022