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7/28/2019 TC2-5 - Slope Stability Guideline
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ST IVES GOLD MINESLOPE STABILITY GUIDELINES
Document No: SIG-EHS-GU013Document Owner: Senior GeotechnicalEngineerRevision No: 2Issue Date: 23/05/07Page: 1 of 36
UNCONTROLLED COPY - PRINTED 23/06/10 REFER TO INTRANET FOR LATEST REVISION
Filename: http://sgmmoss.gfa.local/docs/Occupational Health and Safety/SIG-EHS-GU013.docx
SLOPE STABILITY GUIDELINES
SIG-EHS-GU013
Revision Approved Date Description
0 A. Vasey 19/04/1999 Approved and Current
1 D. Watts 19/09/2005 Approved and Current
2 D Watts 23/05/07 Approved and Current
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ST IVES GOLD MINESLOPE STABILITY GUIDELINES
Document No: SIG-EHS-GU013Document Owner: Senior GeotechnicalEngineerRevision No: 2Issue Date: 23/05/07Page: 2 of 36
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TABLE OF CONTENTS
1.0 OVERVIEW ........................................................................................................ 4
1.1 DOSSIER DETAILS ......................................................................................... 5
2.0 GUIDELINES FOR DATA COLLECTION .......................................................... 6
2.1 EXPLORATION AND PREFEASIBILITY STAGE ..................................................... 62.2 FEASABILITY AND DESIGN STAGE ................................................................... 82.3 SEISMIC STUDIES........................................................................................ 112.4 UNDERGROUND MINING AND KNOWN VOIDS ................................................. 122.5 ADDITIONAL INVESTIGATIONS ....................................................................... 12
3.0 GUIDELINES FOR SLOPE STABILITY ANALYSES ...................................... 12
3.1 INTRODUCTION ........................................................................................... 123.2 RISKASSESSMENT ..................................................................................... 123.3 IDENTIFICATION OF POSSIBLE FAILURE MECHANISMS..................................... 123.4 SLOPE DATA COLLECTION AND INTERPRETATION........................................... 133.5 STABILITYANALYSIS METHODS .................................................................... 13
4.0 GUIDELINES FOR SLOPE MONITORING ...................................................... 15
4.1 INTRODUCTION ........................................................................................... 154.2 VISUAL INSPECTIONS................................................................................... 154.3 SURVEY MONITORING TECHNIQUES.............................................................. 154.4 INSTRUMENTAL MONITORING TECHNIQUES ................................................... 164.5 PIT WALL AND PIT FLOOR PILLAR MONITORING ............................................. 164.6 MONITORING TECHNIQUE REVIEWS .............................................................. 16
5.0 GUIDELINES FOR INVESTIGATING AND MINING THROUGH VOIDS ......... 16
5.1 VOID INVESTIGATION ................................................................................... 175.2 VOID INVESTIGATION TECHNIQUES ............................................................... 185.3 GUIDELINES FOR VISUAL INSPECTION OF VOIDS ............................................ 185.4 GUIDELINES FOR PROBE DRILLING FOR VOIDS .............................................. 185.5 GUIDELINES FOR SURVEYING OR GEOPHYSICAL INVESTIGATION OF VOIDS....... 195.6 GUIDELINES FOR MINING THROUGH FOR VOIDS ............................................. 195.7 GUIDELINES FOR PIT PLANNING ................................................................... 20
6.0
GUIDELINES FOR CORE LOGGING AND EXPOSURE MAPPING ............... 20
6.1 DRILL HOLE SURVEYING,LOGGING AND PRESERVATION OF DRILL CORES....... 206.2 PHOTOGRAPHY OF DRILL CORES ................................................................. 206.3 STANDARD CODES AND DATABASE............................................................... 246.4 GEOTECHNICAL DATABASE SYSTEM ............................................................. 29
7.0 APPENDICES .................................................................................................. 30
7.1 APPENDIX 1EXAMPLE OF A SLOPE STATUS REPORT................................... 317.2 APPENDIX 2EXAMPLE 1SLOPE RISK AND HAZARD MATRIX ...................... 327.3 APPENDIX 2EXAMPLE 2SLOPE RISK AND HAZARD MATRIXNATURAL
SLOPES ..................................................................................................... 33
7.4 APPENDIX 2PROFORMA SLOPE RISK AND HAZARD MATRIXROCK SLOPES 347.5 RANKING GUIDELINES AND EXPLANATORY NOTESROCK SLOPES ................ 35
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ST IVES GOLD MINESLOPE STABILITY GUIDELINES
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ST IVES GOLD MINESLOPE STABILITY GUIDELINES
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1.0 OVERVIEW
A Slope Stability Dossier is a collection of data and documents on a slope orgroup of slopes organised and stored in a standard way.
Its purpose is to make it easier to:
Rapidly access or check previous work on the slope
Keep track of the status of each slope
Monitor progress of work on slope stability issues.
It is a requirement of the Slope Stability Standard that a Slope Stability Dossierbe maintained for all slopes as part of the Slope Management System and thatall data and documents relating to slope stabilities be indexed and stored in theslope stability dossier. The Slope Standard also requires that the Guidelines forData Collection be followed which in turn specifies the indexation and storageof data, reports and documents in a slope dossier.
On a typical mine/project site there may be several dossiers covering differentgroups of slopes, for example:
Dossier 1 Pit XXXX slopes
Dossier 2Pit YYYY slopes
Dossier 3 Stockpiles
Dossier 4Dumps
Dossier 5 Water and tailings storages
Dossier 6Natural and modified slopes
The grouping of slopes into different dossiers is recommended to allow ease ofaccess, reporting and clear identification of responsibilities. Grouping alsoallows a dossier to be closed and archived.
For ease of use, all slope dossiers have a standard structure with the followingsections:
1. Slope status reports
2. Slope identification plan
3. Slope risk and hazard assessment4. Cross reference index of the document collection
5. Incident reports
6. Minutes of slope status meetings
7. Slope management instructions
8. Action plans
All file notes, drawings, photographs, SWPs and relevant reports will becontained in a document collection
The physical document collection should be securely stored in a cupboard or
filing cabinet with an index and a section for recording all material borrowedfrom the collection (Item, borrower, date taken, date returned).
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1.1 Dossier Details
Section 1 - Slope Status Report
This is a tabulated summary of the current status of slopes (see examplebelow).
Section 2 - Slope Identification Plan(s)
Pit or site plan(s) showing the location/identification of the slopes.
Section 3 - Slope Risk and Hazard Assessment
There are a variety of risk assessment tools that can be used to assess therisks associated with slope failures.
The Slope Risk and Hazard Matrix developed for the various types of slopes(examples in this guideline) is intended to provide a simple means to indicateslopes that are potentially hazardous to personnel if they fail
Identify which slopes should be monitored
Facilitate setting of priorities for any outstanding work pertaining to slopesafety.
The first step in assessment of slope stability is to use the Slope Matrix. Thematrix is revised as work on the slope proceeds or as conditions change.
The matrices are divided into four sections:
1. An assessment of the potential for causing serious injuries or fatalities isgiven by the rating.
2. An assessment of slope vulnerability to failure. Category 1 slopes are themost vulnerable to failure and Category 5 the least. This categorisationserves two purposes:
- as a baseline indicator of the likelihood of a slope failure, and- to set the standards required for data collection and analysis in the slope
stability assessment, and the minimum standards required for slope safetymeasures.
3. Slope Stability Data in which the quality of the data used for slope stabilityassessments are ranked according to a set of guidelines. The mostvulnerable Category 1 slopes require the highest level of confidence in the
data and would be ranked I and Category 5, the lowest level of confidence(Rank 5). This serves to highlight where the data may be deficient. ie Allinput data for a Category 3 slope stability assessment should have a rank of3 or less.
4. A Slope Safety Assessment in which the factors affecting the safety of theslope of the slope are ranked. This serves to highlight where catch berms,cable bolts etc require attention. ie All safety features on a Category 3 slopestability assessment should have a rank of 3 or less.
There are four types of Slope Risk and Hazard Matrices:
Rock slopes
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Soil slopes, waste dumps, leach pads, stockpiles and earth embankments(ordinary and water retaining structures)
Tailings storage embankments
Natural slopes
An example of a completed matrix, proformas for the four matrices and theguidelines are given below. There are a variety of additional risk assessmenttools that can be used to compliment the Risk and Hazard Assessment.
Section 4 - Cross Reference Index of the Document Collection
The purpose of this index is to ensure that all related technical information/datais clearly referenced and can be easily found when required.
Sites will need to develop their specific index headings. Suggested headingsinclude:
Slope Stability Analyses
Geological structures and structural analyses
Risk areas identified in reports requiring further investigation
Materials test work
Hydrology, hydrogeology and groundwater
Seismic risk assessments
Slope design parameters and slope reinforcement designs
Slope stability monitoring and leading indicators
Slope failuresSlope remedial works
Section 5 - Slope Incident Reports
This is a compilation of all incident reports.
Section 6 - Minutes of Slope Status Meetings
These may be the full minutes or extracts from the minutes of slope statusmeetings.
Section 7 - Slope Management Instructions
This is a compilation of slope management instructions.Section 8 - Action Plans
This is a compilation of action plans relating to slopes.
2.0 GUIDELINES FOR DATA COLLECTION
2.1 Exploration and Prefeasibility Stage
It is important not to lose the opportunity to collect information that laterdevelopments on the site may obscure. This information may have a bearing on thecourse of future investigations and ultimately slope stability and safety. Furtherearthworks may obscure fault or shear exposures, sinkholes, old mine workings, old
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landslides and groundwater seeps. Copies of all reports, maps, logs, photographsand records shall be preserved for future reference in a secure place. There are fourareas where opportunities to collect data may be lost due to the development of the
site:
2.1.1 Geological and Geotechnical Mapping
All available exposures in the project area and vicinity are geologically andgeotechnically mapped and interpreted if sufficient data is available:
Feature checklist: Rock or soil types Nature and orientation of structures: faults and shear zones, joints,veins, bedding and foliation. Lineaments and drainage lines
Exposure checklist: Outcrops and stream beds Costeans Road and drilling pad cuttings Exploration adits and other workings.
2.1.2 Topographic Mapping
All topographic features should be mapped, and relevant local history regardingthe mapped features recorded. Aerial and site feature photographs should beretained of the undisturbed site.
Feature checklist:
Topography and surface features Sinkholes and caves Mine workings Landslides and slips Surface water ponding, channels, springs and groundwater seeps.
2.1.3 Drill Cores
It is important that for any potential mining project, all drill holes are surveyed,and the cores properly logged, photographed and stored, so that informationmay have a bearing on the course of future investigations and ultimately slopestability is not lost. The Guidelines for Core Logging and Exposure Mapping
(see below).shall be followed. The following basic geotechnical data shall belogged:
Interval (from to)
Core recovery
Rock type
Alteration
Weathering
Fracturing, crushing or shearingAll the properties required for rock mass classification in all major classificationsystems, vis the NGI (Bartons) Q system, CSIR (Bieniawskis) RMR system,
GSI (Hoek) and the MRMR (Laubschers) Mining Rock Mass Classificationsystem.
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All major structures should also be individually logged as geotechnical zones ifwide enough, or as single features with the following items recorded:
Depth or depth interval (or distances)Intersection angle (alpha angle) or orientation
Structure type (fault, shear zone etc.)
Brecciation, shearing, infill strength and width
Wall rock alteration and weathering
Evidence of waterAdditional geotechnical items to be logged if present:
Stress induced core discing, borehole caving orborehole breakouts
Variations in rock densities and porosity.
2.1.4 Hydrology and HydrogeologyComplete histories of rainfall and stream flows are important:As soon as a presence is established on site, start recording rainfall andwater flows
Collect and record historical and anecdotal rainfall and water flow data
Monitor groundwater levels and quality in drill holes
Drawdown measurement with groundwater pumping tests.
2.2 Feasability and Design Stage
In a feasibility study all aspects, which could affect slope stability, should beinvestigated or identified for future investigation and the slope stability dossierinitiated. Specific site investigations are required to determine foundationconditions for treatment plants, dumps, dams and tailings storage facilities.Specialist civil engineering geotechnical consultants normally undertake theseinvestigations. These investigations should also address slope stability issuesespecially in high relief terrain. In the design stage further data collection maybe required to improve the quality of data and to fill gaps identified during thefeasibility study. However, due to practical limitations there may still be areasthat cannot be fully investigated (previous underground mining is a case inpoint). These should be identified for investigation during the early constructstage to address any deficiencies. Key areas include:
2.2.1 Topographical Mapping
Detailed ground or aerial topographical survey maps are essential prerequisitesfor other data collection. These should show all surface features including:
Cuttings, embankments and drains
Sinkholes
Mine workings
Landslides and slips
Surface water ponding areas and groundwater seeps and springs.The scale of the maps should allow all surface features to be shown insufficient detail for project planning and with contour intervals that allow forrecognition of drainage courses and areas of potential flooding. Ideally, themaps should be prepared in the following formats:
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Drafting film for working plans
Digital strings for importation into mine planning software
Digital GIS model for data presentation and other studies.
2.2.2 Geotechnical Model
A geotechnical model is a simplified representation of the real rock and soilproperties in the project area, in which the area is subdivided into several zones(ordomains) with similar geotechnical characteristics. It is based on an analysisand interpretation of the results of geological and geotechnical mapping andlogging programmes. All available exposures and drilling data should be lookedat and considered in this interpretation. A well-distributed and representativerange of exposures, costeans and diamond drill cores should be selected andgeologically and geotechnically mapped or logged. The specific objectives ofthis mapping and logging are to:
Understand project area geological structure the distribution andrelationships of the main rock and soil types, the nature and location offaults, folds and inflections, facies changes, effects of weathering, etc.
Determine the location, orientation, and nature of major structures (e.g.faults, shear, and crush zones, material contacts and weak beds)
Identify and define structural domains and characterise the materialswithin them.
The required standard for the geotechnical mapping and logging is the BasicGeotechnical Logging Standard (see detailed description below).
The proportion of the surface exposures and exploration and resourceevaluation diamond drill holes that should be geotechnically logged is sitedependent. In all cases, it should be sufficient to identify all major structuresand to define domainsand characterise the rocks within them. In some cases additional geotechnicalholes may be required to investigate specific structures or fill in gaps in thedistribution of source data.
2.2.3 Materials Testing
Tests are required to form the basis for estimates of the physical properties of
the soil or rock in each domain. Durability tests to check the potential for loss ofstrength due to exposure, desiccation etc. may be required. Elastic moduli mayalso be required for modelling of stress in rock slopes. The test work shouldcomprise both field index tests and laboratory tests on a suite of representativesamples of all major materials. The choice and numbers of tests are dependenton the project ground conditions. Tests are to comply with Australian orInternational Standards. Ideally, sufficient tests should be performed on eachmaterial to provide confidence in the estimates of the material strengths.
2.2.4 Detailed Structural (Defect) Surveys and Analyses
In hard rock domains slope stability is likely to be structurally controlled with themain failure mechanisms being toppling, planar, wedge or steppath failures on
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faults or shears, bedding and joints or a combination of these. For the design ofslopes in these materials the orientation, spacing, continuity and shearstrengths are required for:
Major structures, faults, shear and crush zonesBedding planes and weak strata
Foliation partings
Joints and veins.The data collection programme should include:
Structural and geotechnical line or face mapping of representativeexposures and costeans. Estimates of joint continuities can only beobtained from
exposure mapping
Geotechnical and structural logs of orientated diamond drill cores which
are representative of the rock types in each of the hard rock domainsSpecial geotechnical drill holes where required to provide an unbiasedsampling of the structures and to fill in any gaps in the coverage
In poor ground where the core orientation is not possible, applicabledownhole geo-physical and sonic logging techniques such as the sonic.Televiewer should be considered.
The Structural Mapping and Orientated Core Logging Guidelines (see below)shall be used for the geotechnical mapping and logging. This also detailsthe requirements for orientated core drilling. The proportion of the surfaceexposures, exploration and orientated cores that are mapped or logged, should
be sufficient to identify and characterise the joint sets and major structures ineach domain. The drill holes should be orientated to ensure that criticaljoint sets and bedding or foliation planes are adequately sampled. In somecases supplementary geotechnical holes may be required to investigatespecific structures or fill in gaps in drilling coverage.
2.2.5 Stress Regime
High stresses can affect pit slope stability. Evidence of high stresses may beseen in discing in drill cores or borehole breakouts (frequently called caving).If high stresses are indicated, stress measurements may be required.
2.2.6 Hydrogeology InvestigationsGroundwater pressures can have a significant effect on the stability of slopes.These have to be taken into account in slope stability analyses and slopedesign. The design may incorporate water controls, slope drainage and/ordepressurisation measures where appropriate. The following aspects should bedetermined:
Sources of water
Current water table(s)
Potential phreatic surfaces
Design criteria for wall rock drainage or wall depressurisation
The potential for slope destabilisation by surface water ingress, erosion,flooding.
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Checklist of items to be investigated:
Cavities, caves and channelled water
Underground mine workings
PaleochannelsPerched water tables
Location and nature of aquifers and aquitards
Water quality.Test work may include packer, pump and air lift tests to determine porosity,permeabilities, storativity of the main aquifers and water bearing structures.
2.2.7 Surface Hydrology
Slope stabilities can be affected by erosion arising from storm and floodwatersand the replenishment of groundwater. Adequate drainage and floodwater
control measures should be incorporated in the site planning. The catchmentarea should be monitored for changes, which may increase the flood risk ormodify the groundwater levels. Checklist of items to be investigated andmonitored:
Stream catchment areas
Rainfall data
Snow and ice accumulations
Stream gradient profiles, bed characteristics and debris accumulations
Lakes and depressions
Man made modifications bridges, dams, embankments, roadformations and subsequent alterations
Stormwater and water supply pipelines.Reports and aerial photographs and/or GIS models of the catchment andproject areas shall be placed in the Slope Stability Dossier for the purposes ofchange monitoring.
2.3 Seismic Studies
Seismic risks should be assessed in terms of the regional geology, especiallyseismically active faults, and by probabilistic analyses of the earthquake record. Inlow seismic risk areas, the published studies may be sufficient, but in seismically
active areas, a seismic study for the project is required to provide the followingdesign parameters. Open pits, modified and natural slopes:
Earthquake magnitudes and return periods
Peak particle accelerations
Soil and topographic amplification factors
Material properties.Dams and tailings dams:
Magnitudes and return periods
Maximum credible earthquakes
Design base earthquakes
Spectral accelerationsMaterial properties.
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Refer to WMC Guidelines for the Design of Tailings Storages
2.4 Underground Mining and Known Voids
Where there are voids in the vicinity of the proposed pit, dumps, tailings facilities andother slopes there should be a thorough search for all existing information. Wherethere is incomplete or insufficient information available specific investigations will berequired. (see Guidelines for Investigating and mining through voids). Duerecognition should be taken of the probability that:
The actual limits of mining may differ from the plans due to subsequent miningor stope collapses
Stope filling is incomplete.The data should be assessed and recorded in the study documentation and SlopeDossier for further detailed investigation.
2.5 Additional Investigations
There may be a requirement for specific or special investigations. These should beidentified in the study documentation to ensure they are conducted at the appropriatetime.
3.0 GUIDELINES FOR SLOPE STABILITY ANALYSES
3.1 Introduction
The steps in slope stability analysis generally include (but may not be limited to):
Risk assessment (Hazard and Risk Matrix or other appropriate assessment)Identification of possible failure mechanisms and appropriate analysismethods
Data collection and interpretation
Material testing
Back analyses
Stability analysis methods
A re-assessment of the hazard and risks
Recommendations for action or design
Documentation
Where a deficiency in the data is identified, this will need to be addressed,and the slope stability analysis repeated.
The related procedures outlined in WMCs GL 68 must also be followed for thedesign of tailings dams.
3.2 Risk Assessment
As a guide to appropriate slope stability analysis methods, the slope stability riskand hazard rating should be used and complimented with a relevant technicalstandard method(s).
3.3 Identification of Possible Failure Mechanisms
The best data available should be used to determine the possible failuremechanisms at the site in question. The following is a checklist of the possible
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mechanisms:
3.3.1 Soil and Granular Materials, also Highly Fractured Rocks
Circular failuresNon circular failures
Combined failure slip circle and a weak substratum or fault
Two wedge e.g. for spoil piles
Liquefaction.
3.3.2 Rock Slopes
Rotational failures on substratum or fault
Planar failures
Step-path failures
Wedge failuresToppling failures
Ravelling failures
Rock falls.
3.4 Slope Data Collection and Interpretation
Further data collection and or testing programmes may be required to meet thespecific requirements of the analyses. Common data requirements for both granularand rock slopes are:
Slope geometry and the location of tension cracks
Slope material profiles and propertiesKnowledge of geological structures
Ground water profiles
Seismic information.The data requirements for slopes in soils and granular materials differ from rockslopes.
3.4.1 Granular Materials
Mohr-Coulomb strength parameters are usually required. In fine-grained soils,these can be determined by laboratory triaxial strength tests on undisturbedsamples. These should be threestage drained or undrained tests asappropriate to the slopedrainage conditions. In highly fragmented rock, the MohrCoulomb strengthscan be estimated by an empirical method(s).
3.4.2 Rock Slopes
Joint orientation data, joint spacing and continuity data, joint shear strength testdata, (or estimates of joint strength data from joint properties) are required.
3.5 Stability Analysis Methods
The analysis methods and path followed is dependent on the risk of slope
failure and the failure mechanism. The greater the risk the more rigorousthe analysis process. This may include multiple and sensitivity analyses.
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Analysis methods may include but are not limited to:
Precedence or slope experience
Empirical
KinematicNumerical (deterministic or probabilistic)
Dynamic
Time dependant.For example the following may apply:
3.5.1 Low-Risk Slopes
For these slopes it may be sufficient to use slope design charts such asdescribed in Hoek, E. and Bray, J. (1981), Rock Slope Engineering, revisedthird edition, Institute of Mining and Metalurgy. Where there are no geological
complications, Haines and Terbrugges RMR (1995) based slope anglecharts can also be used. Haines A. (1993) Rock Slope Classification forOptimum design ofmonitoring networks in Swedzicki, T. 1993GeotechnicalInstrumentation and Monitoring in Open Pit and Underground Mining, BulkemaISBN 90 5410 3213).
3.5.2 Medium to High-Risk Slopes
More rigorous processes including computer based methods should be used. Inmedium risk slopes these can be deterministic, but probabilistic methodsshould be included in higher risk slopes. There is an increasing number ofcomputer packages for the analysis of slope stability. It is important to choose
the most appropriate package(s) for the expected failure mechanism. Whereverpossible, the analyses should be repeated on another package. The slopestability analysis packages should allow modelling the effects of the following:
Position and depth of a tension crack
Water in the tension crack
Blasting and seismic loading
Ground water pressures
Different materials and properties
Geological structures.In seismic risk areas, the effects of earthquake forces should be investigated. In
medium risk slopes, it is sufficient to treat seismic forces as pseudo static forces, butin high-risk soil slopes dynamic modelling of the slopes may be required. The effectof topographic amplification factors should be considered. (Davis L. L. and West L.R. Observed effects of Topography on ground motion, bull. Sesm. Society ofAmerica, 63, 1, pp. 283289). In weaker rocks or high stress areas, two or threedimensional stress/strength analyses should also be performed. Destabilisingeffects of voids requires special and rigorous consideration.
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4.0 GUIDELINES FOR SLOPE MONITORING
4.1 Introduction
The objective of slope monitoring is the early detection of developing hazards andidentification of sections of slopes that may be approaching instability so thatappropriate precautions can be taken. The Slope Risk and Hazard Matrix (seeabove) can be used as a guide to identify those slopes that will need to be regularlyinspected and/or monitored. Some instrumentation may also be required. Thenature of the hazard will determine the frequency and type of monitoring.
4.2 Visual Inspections
Regular inspections of slopes should be carried out to check:
For potentially hazardous loose rocks
For deterioration in the condition of slopes due to weathering, erosion,undercutting, loosening or blast damage
The condition of berms and capacity of the berms to catch and hold scat andminor batter failures
For corrosion of reinforcement
Opening cracks and subsidence in crests, berms and haul roads as anindicator of possible impending failures.
The appearance of cracks can be an early sign of a major failure developing and it isessential that the development of the cracks be monitored. This may be done by:
Recording the number of cracks and their widths at regular time intervals. This
is suitable for low hazard potential failuresEstablishing a number of line traverses and logging the cracks (location andwidth) along each traverse. Repeating the logging at intervals will indicatewhether the slope is stabilising or deteriorating.
Crack dilation monitoring instruments (e.g. measurement between pins driveninto the ground and/or simple surface extensometers or other crackmonitoring devices such as glass plates, wedges )
Displacement monitoring by survey or extensometers.
4.3 Survey Monitoring Techniques
The most common method of pit wall monitoring is to use a total station (ElectronicDistance Measurement (EDM)/theodolite) to measure the distances from a basestation to an array of survey markers (corner cube reflectors or prisms) mountedon the slope. It is critical that the EDM technique has an accuracy and precisionappropriate to the expected rate and magnitude of displacement. The minimumrequirements for the system are:
Survey base stations located on stable ground, or the means to check thelocation of the base stations by instrumental or survey methods. The basestations are best located opposite the slope to be monitored as the EDMdistance measurements are generally more accurate than the angularmeasurements.
Adequate numbers of prisms located on the potential failure slope. The prismsshould be mounted so that they are not easily disturbed or destroyed by
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deteriorating surface conditions on the slope and sufficient should be installedto cater for the inevitable losses.
The survey results should be graphed or mathematically analysed on a time-displacement basis. Predictions of the time of failure are frequently possible bymanual or mathematical extrapolation of the displacement rates. When progressivefailure conditions become apparent, the monitoring frequency should be increased toimprove the prediction accuracy. Other survey techniques may include:
Precise levelling
Global Positioning System
Triangulation
Photogrammetry.
4.4 Instrumental Monitoring Techniques
There are a large number of instruments available for monitoring such asextensometers, inclinometers, shear detectors, and microseismic monitoring system.These should be installed in accordance with the manufacturer's recommendations.The monitoring programs should include devices capable of monitoring thedisplacement of the slope so that timedisplacement analyses can be done andpredictions of the time of failure made. Where the consequences of a failure couldbe lifethreatening, instruments capable of monitoring slopes continuously and beinglinked to audible and mine radio alarm systems should be used where possible.In earthquake prone areas seismometers linked to audible and mine radio alarmsshould also be used.
4.5 Pit Wall and Pit Floor Pillar Monitoring
Where the pit is close to voids, monitoring of the stability of the pillars is essential.The location size and condition of the voids should have been investigated by probedrilling and/or geophysical or photographic techniques. As each bench is mined, theremaining pillars should be re-investigated by the most suitable of these methods.Generally, pit mining face advances preclude longer term monitoring instrumentssuch as extensometers, inclinometers, and shear detectors. Microseismic monitoringsystems have the potential to remotely monitor failing ground, however these alsopick up other pit operating noises and if these can be filtered out, they could offercontinuous monitoring and links to audible, visual and/or radio alarm systems.
4.6 Monitoring Technique Reviews
Periodic reassessments should be done on the type(s) of monitoring, location anddensity of instruments and frequency of observations. Adjustments should be madewhere necessary.
5.0 GUIDELINES FOR INVESTIGATING AND MINING THROUGHVOIDS
Where there are natural voids or underground mining on a site, precautions need tobe taken to ensure that:
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Open pit mining can proceed safely and stopes or remaining pillars do notcollapse and destabilise the pit slopes above it
The pit floor does not collapse into an underlying stope and endanger the
safety of personnel operating in the pitDumps and tailings storage facilities are not constructed over potentiallyunstable slopes
For the feasibility study, a first pass estimate of the location, size and nature of theprevious workings may be sufficient. This should include a review of theunderground mine plans and stoping data while recognising that the actual limits ofmining may differ from the plans due to subsequent mining or stope collapses.Through out this guideline the titles of Pit Supervisor, Geotechnical Engineer andSurveyor are used in a generic sense. Each operation may have a different title orname for this duty eg may be called Production Engineer or Mine Manager. The
intent is clear in that a person shall designated to have specific responsibility foreach of the steps or activities and be accountable for compliance with the step orprocess. It is critical that relevant experience or qualifications are held by the personcharged with the responsibility.
5.1 Void Investigation
Two or more stages of investigation may be required.
5.1.1 Initial Stage, to determine:
Whether the voids will affect the stability of pit walls and floors or the
safety of personnel working in the pitWhat void investigation techniques are required and can be safely used
Safe working practices for further investigation of the nature and locationof the voids
5.1.2 Advanced Stage
In practice it may be necessary to make some conservative assumptions on theminimum distance in order to develop the pit to a position where the stopes canbe investigated more fully. Probe and or geophysical techniques to determine:
The location and size and nature of the voids or workings to a precision
required for safe mining through the voidsThe state of the voids: the condition of the ground forming the back, walls and pillars the presence of stope backfill, its condition, the degree of stope
filling and presence of water in the stope stope back reinforcement (cable bolting) and its condition
The minimum distance that must be left between the open pit and stopesto ensure the stability of the stopes and stope pillars, open pit walls andfloor. This would normally involve stress and displacement modellingwith measured or estimated in situ stresses and rock mass strengths.
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5.2 Void Investigation Techniques
The following techniques can be used to investigate the location and size of thestopes:
Visual inspection of voids that are safely accessible from underground
Borehole probe drilling (see Probe Drilling SWP below): Purpose drilled probe holes with closed circuit television if the
cavities are not flooded Grade control drilling Blast holes for small openings
Remote cavity surveying techniques: Cavity Monitoring System (CMS ) This requires access to the void
from underground Cavity Auto Laser Scanner (CALS) a 100 mm diameter survey
instrument that can be lowered down a boreholeGeophysical methods
Microgravity
Seismic tomography (e.g. RockVision)
Ground Probing Radar (GPR)
Radio imaging (e.g. RIM II).
Resistivity.
5.3 Guidelines for Visual Inspection of Voids
SWPs shall be developed to ensure the safety of personnel undertaking the
inspections Precautions shall include:Examinations of plans sections etc so that inspection personnel do not enterpossibly unstable undercut areas
Inspection and barring down of development backs to avoid rockfalls
Personnel entering the void periphery wearing safety harnesses with SALAfall arrest blocks and safety lines properly secured to a safe anchorage
5.4 Guidelines for Probe Drilling for Voids
The stages and responsibility for the work shall include:
Examinations of plans sections etc to identify possibly undercut areas anddetermining minimum safe approach distances and planning the investigation
(Responsibility Geotechnical Engineer and /or Pit Supervisor)Marking out the exclusion zones by red and white flagging tape(Responsibility Surveyors)
Marking out the drilling traverse lines (Responsibility Surveyors)
Drilling probe holes at specified intervals and angles and depths specified bythe Pit Supervisor (Responsibility Driller)
Logging the probe holes (Date, driller, Location ie bench, traverse anddistance from start peg, depth to break through depth to floor) (ResponsibilityDriller and/or Sampler)
Reporting voids located to Pit Supervisor (Responsibility Driller and/or
Sampler)
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Plotting of reported cavities and re-examination of plans sections etc todetermine minimum safe approach distances and planning furtherinvestigation (Responsibility Geotechnical Engineer and/or Pit Supervisor)
Maintenance of up to date plans sections etc to determine shoeing voidoutlines, minimum safe approach distances and maintaining up top dateexclusion zone flagging (Responsibility Surveyors)
SWPs shall be developed to ensure the safety of personnel undertaking theinvestigations.
Precautions shall include:
Standing instructions that no one shall enter an exclusion zone marked by redand white flagging tape except certain persons instructed to do so by the pitsupervisor to undertake specific tasks (Responsibility Pit Supervisor)
Safety training of persons required to work in an exclusion zone and provisionof belts and safety lines etc for them (Responsibility Pit Supervisor)
Maintenance of the exclusion zone markers (if any red and white flagging tapeis cut or moved it shall be restored immediately) (Responsibility all pitworkers).
5.5 Guidelines for Surveying or Geophysical Investigation of Voids
The stages and responsibility for the work shall include:
Planning the investigation with due regard for known undercut areas andminimum safe approach distances (Responsibility Geotechnical Engineer andPit Supervisor)
Conducting the investigation and reporting of results (Responsibility
Geotechnical Engineer and Surveyor)Plotting of reported cavities and re-examination of plans sections etc todetermine minimum safe approach distances and planning furtherinvestigation (Responsibility Pit Supervisor).
5.6 Guidelines for Mining through for Voids
The stages and responsibility for the work shall include:
Analysis of all void data to determine a safe mining strategy and detailedplanning (Responsibility Geotechnical Engineer and Pit Supervisor)
Appointment of personnel with specific responsibilities in the plan for mining
through voids. The may include the appointment of a Void Officer tocoordinate work and maintain records on voids. (Responsibility MineManager)
Preparation of SWPs for the safety of personnel mining through andmonitoring the stability of pillars between stope and pit See Guidelines onpillar stability monitoring (ResponsibilityPit Supervisor)
Mining operations and monitoring the stability of voids, pillars and slopes(ResponsibilityGeotechnical Engineer and Pit Supervisor).
Precautions should include:
Exclusion zones shall be marked by red and white flagging tape and no oneshall enter an except certain persons instructed to do so by the pit supervisor
to undertake specific tasks (ResponsibilityPit Supervisor)
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Safety training of persons required to work in an exclusion zone and provisionof belts and safety lines etc for them (ResponsibilityPit Supervisor)
Backfilling of voids This will be a normal procedure except where the void is
too small to fill effectively or there is an obstruction that cannot be removedsafely that will prevent adequate filling of the void (ResponsibilityGeotechnical Engineer and
Pit Supervisor). Standing instructions shall be developed for the placement ofthe back fill (back fill materials, direct tipping, bulldozing etc.) (ResponsibilityPit Supervisor) Until the void is filled to the satisfaction of the GeotechnicalEngineer and Pit Supervisor, the exclusion zone markers shall be maintained(if any red and white flagging tape is cut or moved it shall be restoredimmediately - Responsibilityall pit workers)
Drilling and Blasting Pillars above VoidsSafe and effective procedures shallbe devised for drilling and firing pillars next to or above voids (ResponsibilityGeotechnical Engineer and Pit Supervisor). Standing instructions shall bedeveloped for the drilling and charging (ResponsibilityPit Supervisor) Until thevoid is effectively destroyed to the satisfaction of the Geotechnical Engineerand Pit Supervisor, the exclusion zone markers shall be maintained. Thecurrent Western Australia Department of Minerals and Energy Guidelines forOpen pit mining through underground workings shall be consulted.
5.7 Guidelines for Pit Planning
Pit shall be designed sot that all ramps avoid possibly undercut areas and within a
minimum safe approach distances based on the size and condition of the void andduty of the ramp. (ResponsibilityGeotechnical Engineer and Pit Supervisor).
6.0 GUIDELINES FOR CORE LOGGING AND EXPOSURE MAPPING
6.1 Drill Hole Surveying, Logging and Preservation of Drill Cores
All drill holes used in slope stability assessments should have
Collar positions surveyed
Down hole traces surveyed.
Before the core is cut for assaying, all diamond drill cores shall also be:Geologically and geotechnically logged
Photographed (see Guidelines for Core Photography)
Representative samples of relevant materials are preserved for later testing.The remaining cores after assaying are preserved for further inspection.
6.2 Photography of Drill Cores
High quality and good clear core photographs are invaluable in establishinggeological and geotechnical models. The preferable requirements for good corephotographs are:
One core tray per photo
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Photograph core after core recovery has been measured, depth blocks havebeen checked and before the core is split
Photograph in full sun, but avoid midday sun, as it is difficult to eliminate the
photographers shadows, also avoid early morning and late afternoon as thecolours may be distorted. Photographs on overcast days can produceacceptable results if colours are not critical to rock type differentiation
Use colour print film and print on 100 x 150 mm paper is preferable but digitalphotos may be taken (1.3 to 1.5 megapixel/frame camera with printsreproduced by a colour laser printer on photoquality paper) A colour chartshould be included in the header board to ensure consistent colours duringprinting.
Use a frame to hold the camera directly above the centre of the core tray andheading board for best results, hand held cameras even disposable cameras
can produce acceptable results if used with care
Check that depth blocks are the right way up and not in deep shadow
If the core is orientated, arrange core so that orientation line can be seen
Arrange core tray to avoid shadows across it
Use a heading board to record hole number, tray number and the start andend depths in the core tray and other comments (precollar depths, core loss,EOH etc.)
Preferably place the heading board at the top of the tray, with the start of thecore in the tray at the top left.
Set camera focal length or distance so that the tray almost fills the frame.Check the other camera settings
A light spray of water will enhance colours and help in rock type identification,however, if the rock is dark or black, structures are easier to see in photos ofdry core
Avoid artificial lighting (flash or fluorescent), especially if cores are wet.
Standard Terminology for Geotechnical Mapping and Logging Drill Cores
6.2.1 Introduction
Geotechnical data forms the basis for modelling and is essential in the efficientrunning of mines. This guideline outlines the standard terminology for data.Several terms used in the descriptions below to describe natural breaks in the
rock mass. Defects include schistosity, foliation, bedding, veins, joints andfaults. Discontinuity and fracture exclude schistosity, foliation, but includebedding, veins, joints and faults. Joints is used in the normal geotechnicalsense ie the common discontinuities which define the shape and size of rockblocks.
6.2.2 Data Fields
The following are a list of all the data fields currently used for geotechnical data.The codes only relevant to in-situ measurements are outlined:
Recovered Core Length: total length of core recovered from interval(Recovery is calculated from it)
Core > 10 cm: total length of all core > 10 cm (RQD may be calculated fromit)
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Weathering: degree of weathering
QSI: estimated rock strength (or Qualitative Strength Index)
Fractures per interval: calculates Fracture per metre (FPM) or Joint
SpacingFracture Type: Type of discontinuity
Joint Sets: degree of jointing
Joint Roughness: the nature of the discontinuity wall
Fracture Infill: the type of joint infill and its alteration
Fracture Infill Mineral: the main mineral in the joint
Fracture Thickness: the thickness of the fractures
Fracture Length (only for in-situ measurements)
Fracture Spacing (only for in-situ measurements)
Fracture Termination (only for in-situ measurements)
Seepage: water flow and free moisture in discontinuities or rock mass (JointWater Pressure) (only for in-situ measurements)
Stress Reduction Factor: weakness zones intersecting excavation (only forin-situ measurements)
Angle to Core Axis: angle to core axis (Alpha angle)
Rotation Angle: called also (Beta Angle)
OutputsGeotechnical data is further processed for indexes to quantify rock mass quality.The main currently used indexes are RQD, Q, RMR and MRMR. RQD is thepercentage of core length>10 for the interval. The other indexes require more
complex manipulation as illustrated below:Field Q modified RMR MRMR Structure
Recovery
Core >10cm
Weathering
Rock Strength ()
Fracture/m (FPM)
Type
Number of sets
Joint Roughness
Alteration/ Infill
Infill Mineral
Infill Thickness Seepage ()
Stress Reduction Factor ()
Angle to Core Axis
Rotation Axis
() full Q index
6.2.3 Core Logging for Open pits and Underground Mines
In Underground Mines, all diamond holes should be geotechnically logging within
20 m (true thickness) on either side of the orebody. In Open pits all diamond drill
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holes that intersect the current or possible future pit walls should begeotechnically logged.Logging forms shall designed to capture the following data to allow the rock
mass to be rated in any of the above classification systems. For the hole:HOLE ID: Hole number
LOGGED BY: Name of the logger
DATE: Date of logging
DIAMETER: The diameter of drill core. (Can be obtained from other drillhole information)
HOLE COMMENT:Comment for hole.
For logging intervals (specific to geotechnical logging-does not require to be thesame as assay intervals)
FROM: The start of the downhole interval for similar rockmass
TO: The end of the downhole interval for similar rockmass
CORE10: The total length of core greater >10 cm for RQD
NO / FRACTURES: The number of fractures for interval for fracturefrequency (FPM)
QSI: The ISRM category for estimated UCS
TYPE: The nature of the dominant fracture
NO OF SETS: The number of discontinuity sets
JOINT INFILL:The type of joint infill and its wall rock alteration (gouge,breccia carbonate cement, weathering, chloritic alteration, talcification,argillic or propylitic alterations must be recorded. The nature of the
dominant infill if infill > 1 mm and wall rock alteration if infill < 1 mmTHICKNESS: The thickness of the fracture
ROUGH: The topography of the continuity
COMMENT: Comment for interval.
The above format is very similar to most current geotechnical core logging formscurrently used within WMC. It has to be mentioned that the core recovery anddip and dip direction are not included. The recovery measuring the recoveredcore length can be either captured for the logged interval or for different intervalson a different form e.g. between the drillers core blocks. The dip and dip
direction for oriented cores should also be included with the alpha and betaangles.
6.2.4 Exposure Mapping
In-situ mapping will be performed by line mapping or window mapping. Theinformation is treated like a drill hole information and store in the drill holeGeodata\Geobase database. The following data is recorded for window mappingand the mapper may use the electronic Breithaupt Tectronic compass toreduce the data entry time. For the location (not recorded in electroniccompass):
FACERUN ID: The ID of the mapping location (e.g. Mine prefix + level +
number)MAPPED BY: The mappers name
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6.3.2 Core > 10 cm
The core >10 cm is the total of all the core greater than 10 cm in length, ignoringend of run and core tray breaks, within the interval. Joints that run parallel to the
core axis are to be ignored.
6.3.3 Weathering
Weathering field records the degree of weathering on the rocks. The data entrysystem uses the following codes:
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6.3.4 QSI (Qualitative Strength Index)
The qualitative strength index is an estimating rock strength by index tests as listed
below.
6.3.5 Fracture Number per Interval
The fracture number per interval is the number of discontinuities for the interval.The fracture number per interval is processed to provide fractures per metre.Fracture TypeA fracture is defined as any plane or surface which is now or has been in thepast been broken. Fracture type include joints, veins, faults, shears and beddingplanes. Care must be taken in identifying major structures such as faults andshears as these are the key controlling features in slope stability.
Code joi: Joint con: Lithological Contact zon: Fault or Shear Zone fol: Foliation Discontinuity bed: Bedding Plane Discontinuity vei: Vein Parallel Discontinuity dis: Discrete Fault or Shear
Joint SetsThe joint sets field define the number of joint sets present.. Joints are common
discontinuities which define the shape and size of rock blocks. The codesare based on the Barton Tunnelling Quality Index Q.
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Code mnf: Massive or few joints 1js: One joint set
1jr: One joint plus random 2js: Two joint sets 2jr: Two joint sets plus random 3js: Three joint sets 3jr: Three joint sets plus random 4js: Four or more joint sets, random, heavily joined cre: Crushed rock, earth like
Joint RoughnessJoint roughness refers to the nature of the discontinuity walls and to the smallirregularities on the fracture surface. The codes are based on the BartonTunnelling Quality Index Q. The RMR rating for joint condition is a combination
of joint roughness, fracture infill and fracture infill thickness.Code
rad: Rough and discontinuous smd: Smooth and discontinuous rau: Rough and undulatory ssd: Slickensided and discontinuous smu: Smooth and undulatory rap: Rough and planar ssu: Slickensided and undulatory or gouge filled and
discontinuous smp: Smooth and planar gpu: Gouge filled with nor rock wall contact and planar and
undulatory ssp: Slickensided and planar
Fracture InfillThe fracture infill records the type of joint fill and its alteration. The codes arebased on the Barton Tunnelling Quality Index Q.
Code non: None or tightly healed or hard, nonsoftening, impermeable,
unweathered filling e.g.quartz una: Unaltered joint with surface staining only
sli: Slightly altered or weathered joint walls, hard mineral coating,may include small clay free sandy particles
mod: Silty or sandy clay coating, small clay fraction sof: Soft infill including low friction clay, platy mica, talc, gypsum
and graphite bad: Soft and highly weathered swelling clay filling e.g.
MontmorilloniteFracture Infill MineralThe fracture infill mineral field records the mineral in the fracture. The mineralcodes are the standard WMC legend mineral codes. There are 586 mineralcodes stored in the min.val file.
Fracture Thickness
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The fracture thickness records the thickness of the fracture measure at rightangle to the fracture.
Code
t 5 mm nwc: Sheared with no wall contact or thick zones of decomposed
or highly weathered material.Fracture LengthThe fracture length records the length of the fracture in metres. This is recordedin mapping by in-situ measurements.
Code l
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cont: Indeterminable (continuity).Seepage - Joint Water PressureThe water seepage (or joint water pressure) field is an estimate of the water flow
through the rock. Seepage is an in-situ measurement and is not used incore logging. However it can be used in window mapping.
Code dry: Dry dmi: Damp or minor flow wet: Wet drp: Dripping mip: Medium inflow or pressure lpc: Large inflow/high pressure in competent rock lhp: Large inflow/high pressure ehd: Exceptionally high inflow decaying with time
ehp: Exceptionally high inflow or pressure.Stress Reduction FactorThe stress reduction factor is an indication of the weakness zones which may beloosening of rock mass when a tunnel is excavated. This is an in-situmeasurement but it has been included in the list because it can be used for facerun in future line or window mapping.
Code sr3: single weakness zones containing clay (depth of excavation
> 50 m) sr5: single weakness zones containing clay (depth of excavation
< 50 m) sr2.5: single shear zones in competent rock (clay free) depth of
excavation > 50 m sr5.0: single shear zones in competent rock (clay free) depth of
excavation < 5 0m sr7.5: multiple shear zones in competent rock loose surrounding
rock sr10: multiple occurrences of weakness with clay sr12: loose open joints, heavily jointed or sugar cube.
Angle to Core Axis (Alpha angle)The angle to core axis is the angle between the core axis and the plane of the
fracture. If the rotation angle (Beta angle) is measured, the true dip and dipdirection can be calculated for the plane.Rotation Angle (Beta angle)A plan in the core has an elliptical trace on the surface of the core. The rotationangle is the angle between the reference line and the up hole apex of theelliptical trace. If the angle to core axis (Alpha angle) is measured, the true dipand dip direction of the planar fracture can be calculated for the plane.
6.4 Geotechnical Database System
Data FlowThe data flow of the geotechnical information is summarised below:
1. Log data either on a paper form or in the geological logging system (GLS)2. If it is a paper form, enter the system on the geotechnical data entry system
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3. Send the transaction files either from the GLS or from the geotechnical dataentry system to the Geodata logging update directory.4.The data is then automatically loaded to the Geodata database (e.g. Once a
day)5. Geodata geotechnical logging information is then down loaded automaticallyto the drill_geotech table in Geobase6. Data can be then retrieved automatically or inter actively to aDatamine/Surpac format and include in the current Datamine extract used by alloperations.7. Geotechnical data can be retrieved on plans and sections with Geoview.8. Data can be extracted to a text file to load to Excel spreadsheet or othersoftware package.9. Added value can be input back into the database. For example, it is quitecommon to assign lode codes to an interval (e.g. Hole XXXX from 100.6
to 112.00 lodecode = HV1). Similar practices could applied to geotechnical dataand domain codes could be defined and stored in the database.
7.0 APPENDICES
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7.1 Appendix 1 Example of a Slope Status Report
Slope LocationDate ofLastInspection
Slope Status Action Action StatusResponsiblePerson/s
ActionbyDate
Safety Issues
Rd]
RedeemerNorth wall
31/3/98 Failure imminent -crack width increasingrapidly - lmm/day
Pit abandoned -close haul roadadjacent to northside of pit
Action complete- earth bundsconstructedacross haul roadat two sections
A N Othe r Erect warning signs atbunds - no furthermonitoring - no personnelallowed in vicinity of northside of pit. D Milton toobserve daily and report toRM
Rd3Redeemer eastwall
25Oct1998 Pit slope under reviewwith view to steepenbatter slope
Review ofstability analysisrequired
Review ofanalysis underway - completeby 3/11/98
T. Li 3/11/98 None
Rd4 Redeemer westwall, southernsection
25 Oct1998 Crack observed onberm at RL 220on30/10/98 - crackabout 35m long and 5mm wide
Monitor slopemovementDevelop andimplement SWPfor work invicinity of slope
Action plan to bereviewed andapproved by RMand SEQmanager SWPundercompilationTemporarysafety measuresimplemented
D Milton - ActionPlanP Arthur - SWP
1.2/1i/98
Barriers to be erected toprevent vehicular accessonto berm
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7.2 Appendix 2 Example 1 Slope Risk and Hazard Matrix
SLOPE RISK AND HAZARD MATRIX ROCK SLOPES
Pit Nil Desperandum Slope Sector 1 South East Batters 350-500m
Asse ssor I M Notjoking Revision No - 5 Date 2 Feb 1998
POTENTIAL CONSEQUENCE OF FAILUREPotential Human exposure
SLOPE VULNERABILITY CATEGORYSlope height and steepness
Vulnerability & probability of natural events Likelihood of failure
SLOPE STABILITY DATASlope stability analyses
Confidence level in material strengths Confidence levels in ground water conditions
Confidence level in geological structures Design consideration of natural events
SLOPE STABILITY ASSESSMENTCrest and wall condition
Cable bolt and other supportCatch berm and catch fence conditions
PROTECTION MEASURESProtection fences and warning signs
Slope stability inspection and monitoring Slope specific SWPs
Multiple X None
Regard as an action priority ranking
CategorySteep/ highVulnerable / High
Highly likely
1 2 3 4 5 LowNot VulnerableUnlikely
X
X
X
RankRigorous
KnownKnownKnown
Rigorous
1 2 3 4 5NoneAssum edAssum edAssum edNot Considered
X
X
X
X
X
RankSoundGood
Wide and Clear
1 2 3 4 5Poor/ deterioratingPoor/ deterioratingNarrow or full
X
X
X
Not required Required
Good conditionOperating satisfactorily
In force
X Incomplete/ faultyPlanned/ suspendedPending
X
X
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7.3 Appendix 2 Example 2 Slope Risk and Hazard Matrix Natural Slopes
SLOPE RISK AND HAZARD MATRIX ROCK SLOPESPit Slope Height
Asse ssor Revis ion No Date
POTENTIAL CONSEQUENCE OF FAILUREPotential Human exposure
SLOPE VULNERABILITY CATEGORYSlope height and steepnessProbability of natural events
Slope geological profileLand use effects
Likelihood of failure
SLOPE STABILITY DATAConfidence levels in ground water
Confidence level in geological structuresNatural events in stability assessment
SLOPE STABILITY ASSESSMENTCrest and wall condition
Cable bolt and other supportCatch berm and catch fence conditions
PROTECTION MEASURESProtection fences and warning signs Slope stability inspection and monitoring
Slope specific SWPs
Multiple X None
Regard as an action priority ranking
CategorySteep/ high
High/ criticalHazardous
1 2 3 4 5LowLow Sound
X
X
X
Critical X Minimal
Highly likely X Unlikely
RankKnownKnown
Known & Considered
1 2 3 4 5Assum edAssum edIgnored
X
X
X
RankSoundGood
Wide and Clear
1 2 3 4 5Poor/ deterioratingPoor/ deterioratingNarrow or full
X
X
X
Not required RequiredX Good condition
Operating satisfactorilyIn force
Incomplete/ faultyPlanned/ suspendedPending
X
X
Note: Likelihood of failure. Use lowest category.
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7.4 Appendix 2 Proforma Slope Risk and Hazard Matrix Rock Slopes
SLOPE RISK AND HAZARD MATRIX ROCK SLOPES
Pit Slope BattersAsse ssor Revi sion No Date
POTENTIAL CONSEQUENCE OF FAILUREPotential Human exposure to failure
SLOPE VULNERABILITY CATEGORYSlope height and steepness
Vulnerability & probability of natural events Likelihood of failure
SLOPE STABILITY DATASlope stability analyses
Confidence level in material strengths Confidence levels in ground water conditions
Confidence level in geological structures Design consideration of natural events
SLOPE STABILITY ASSESSMENTCrest and wall condition
Cable bolt and other supportCatch berm and catch fence conditions
PROTECTION MEASURESProtection fences and warning signs Slope stability inspection and monitoring
Slope specific SWPs
Multiple None
Regard as an action priority ranking
CategorySteep/ high
Vulnerable / HighHighly likely
1 2 3 4 5LowNot VulnerableUnlikely
RankRigorous
KnownKnownKnown
Rigorous
1 2 3 4 5NoneAssum edAssum edAssum edNot Considered
RankSoundGood
Wide and Clear
1 2 3 4 5Poor/ deterioratingPoor/ deterioratingNarrow or full
Not required Required
Good conditionOperating satisfactorily
In force
Incomplete/ faultyPlanned/ suspendedPending
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7.5 Ranking Guidelines and Explanatory Notes Rock SlopesRanking/ Category 1 2 3 4 5
POTENTIALCONSEQUENCE OFFAILURE
Multiplefatalities in amajor failure
Single fatailityin a majorfailure
Serious LTI Possible LTI orMTI No injuries orloss
SLOPEVULNERABILITY
Ranking based on factors of safety, probablility of sliding or assessed stability relativeto other slopes on site, taking into consideration the possible consequences a major
failure. The possible influences of underground mining must be considered.
Slope height andSteepness
FoS50% or
severecracking or
failing
FoS=1.2-1.5 orPoS>20-50%
or minorcracking
FoS=1.5-2 orPoS>5-20%Apparently
stable
FoS=2-3 orPoS>0-5%Apparently
stable
FoS>3 orPoS>0-5%
Stable
Vulnerability &
probability of naturalevents
Critical and>=1 in slope
life
Vulnerableand >=1 inslope life
Vulnerableand >=1 in 100Years
Vulnerable or>=1 in 100Years
Not vulnerableor
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fracturedrock
Cable and othersupport
Condition of cable bolting, mesh, shear pins or catch fences
Sound/ notrequired
Mildcorrosion ordeterioration
Moderatecorrosion ordeterioiration
Heavycorrosion
Severelycorroded
Catch berm andcatch fence
condition
Capacity of berm to hold scat and rock falls
Wide/ clear Fall Capacity20 BCM/m
Fall Capacity10 BCM/m
Fall Capacity5 BCM/m
Narrow/ full