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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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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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


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


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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Document No: SIG-EHS-GU013Document Owner: OHS CoordinatorRevision No: 1Issue Date: 08/09/2005Page: 31 of 36



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



PROTECTION MEASURESProtection fences and warning signs Slope stability inspection and monitoring

Slope specific SWPs

Multiple X None


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


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



PROTECTION MEASURESProtection fences and warning signs Slope stability inspection and monitoring

Slope specific SWPs

Multiple None


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


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

TC2-5 - Slope Stability Guideline

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