Designing and Benchmarking Mine Roads for Safe and Efficient Haulage Roger Thompson Alex Visser Departments of Mining and Civil & Bio-systems Engineering University of Pretoria, South Africa Aim of Presentation An overview of industry best-practice in haul- or roadway As a basis for reducing accident potential associated with poorly roads 1
Scope of Presentation Introduction Mine Road Design Categories Transport and Mining Accident Stats Mine Haul Road Safety Audit System Conclusions Introduction - application scenario Historically, mine road was empirical, ad- hoc and not always focused on the accident potential of poor work Traffic volumes are low, but highly variable over an extensive network of unpaved roads 2
Introduction - application scenario Historically, mine road was empirical, ad-hoc and not always focused on the accident potential of poor work Mine Road Design Categories BASIC DATA Geometric Modify wearing course selection Structural Functional Maintenance Management System Chemical palliation Palliative Performance Model Dust Model Dust Palliative Management Water-based spraying Within limits no treatment required Components of a mine road include; geometric (alignment) structural (thickness and strength) functional (surfacing) maintenance management (blading, grading) 3
Integrating the Categories of a Haul Road Design BASIC DATA Geometric Modify wearing course selection Structural Functional Maintenance Management System Chemical palliation Palliative Performance Model Dust Model Dust Palliative Management Water-based spraying Within limits no treatment required What are the safety critical issues in road? BASIC DATA Geometric Modify wearing course selection Structural Functional Maintenance Management System Chemical palliation Palliative Performance Model Dust Model Dust Palliative Management Water-based spraying Within limits no treatment required 4
What are the safety critical issues in road? Geometric Structural Functional Berm Wearing course selection Vertical and alignment Wearing course dust treatments Horizontal and alignment sight distances Skid resistance and loose material - stoniness Geometric Design Use a structured approach to geometric ; Firstly, a set of mine geometric standards Secondly, the conceptual Finally, the as-built 5
Truck minimum braking distances (unassisted) Truck typical speeds up- and down-grade Truck sight distance requirements Lay out the road according to 9-11% max sustained grade Assume initial width of road 4,5x width of truck including berms and drains Highlight location of Switchbacks Curves (horizontal and vertical) Intersections Locate switch-backs on section of road with no vertical grades Conceptual road vertical and horizontal layout Separate vertical and horizontal curves where possible Intersection Drainage Locate intersections on level with adequate sight, curves and run-out. Design drainage system, especially road-side, culvert location, switchback and intersection drainage. Examine conceptual following vertical and horizontal alignment requirements Design berms (median and outslope) with largest truck and speed in in mind. Berm Vertical and alignment Establish optimum grade 9-11%,. Establish minimum vertical curve lengths based on change in in grade (%) or headlight distance for sag curves, for minimum stopping distance For every 1% increase in in rolling resistance over 2%, reduce optimum grade by 1% Where pit geometry does not allow for minimum requirements, apply speed limit to each curve not meeting requirements Horizontal and alignment Drainage re-evaluation evaluation Final geometric Establish width of road according to; Truck width Traffic (1-2 lanes) Safety berm at outslope and centre of road Establish minimum horizontal curve layback based on braking distance Establish cross-fall value or camber (2-4%). Laden lane at uphill side of crossfall. Establish minimum horizontal curve radius based on speed of truck and superelevation (5% max) Establish run-outs based on curve superelevation, cross-fall and camber. Where pit geometry does not allow for minimum requirements, apply speed limit to each curve not meeting requirements Where pit geometry does not allow for minimum requirements, apply speed limit to each curve not meeting requirements 6
Geometric Design Well documented but take special care with; Ramps width, junction visibility, spillage and drainage Geometric Design Well documented but take special care with; Ramps width, junction visibility, spillage and drainage Switchbacks and curves larger radius, super-elevated elevated and sight / stopping distances 7
Geometric Design Well documented but take special care with; Ramps grade breaks and max productive total resistance (grade + rolling) Switchbacks and curves larger radius, super-elevated elevated and sight / stopping distances Geometric Design Berms especially centre berms large enough to arrest vehicle but visibility issues for smaller vehicles 8
Geometric Design Berms especially centre berms large enough to arrest vehicle but visibility issues for smaller vehicles Drainage cross-fall or camber and roadside drainage ditches Geometric Design Berms especially centre berms large enough to arrest vehicle but visibility issues for smaller vehicles Drainage cross-fall or camber and roadside drainage ditches 9
Geometric Design Make sure that what you have ed is built and maintained correctly Make use of signage to assist grader and truck operators to make maximal use of the road Structural Design Load carrying capacity of the road. Design for; Better pavement response to applied loads Reduced deflection on surface and deformation in sub-grade or in-situ = Better directional stability of truck 10
Structural Design Case Study W/course Selected blasted waste rock Layer 3 In-situ Wearing course New Design Layer Depths (mm) 0 250 500 750 1000 1250 1500 1750 2000 2250 2500 Wearing course Base Structural comparisons 0 In-situ (soft) 250 500 750 1000 1250 1500 1750 2000 2250 2500 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Old Design Layer Depths (mm) W/course Fill layer Layer 3 In-situ Base Vertical (micro) strain in pavement In-situ (soft) Old Design New Design Functional Design Wearing course material selection. Design for; Reduced wearing course defects especially dustiness and loose material Reduced deterioration rates and maintenance frequency 11
Functional Design Shrinkage Product. 400 350 300 250 200 150 Dustiness Wearing Course Selection Slippery when wet 100 Loose stones 50 Tyre damage Corrugates Loose material 0 0 5 10 15 20 25 30 35 40 45 50 Grading Coefficient Recommended (1) Recommended (2) Practical Application Shrinkage product. 550 500 450 400 350 300 250 200 150 100 50 0 Wet skid resistance Dustiness Loose stoniness 2 Loose material Corrugations Dry skid resistance 0 10 20 30 40 50 Grading coefficient 1 12
Practical Application Shrinkage product. 550 500 450 400 350 300 250 200 150 100 50 0 Dustiness Loose stoniness Dry skid resistance 0 10 20 30 40 50 Grading coefficient 1 Practical Application Consider the use of dust palliatives to improve wearing course performance BUT; Will not fix an inherently poorly road (expensive) Require dedicated and modified road management approach one product doesn t fit all types of applications 13
Transport & Mining Accident Statistics About half of all attributable transport accidents are road- related; Geometric problems Functional problems Human error Non-standard practices Percentage of road factors implicated in attributable T&M accidents Geometric 10% Not attributable 53% Road related accidents 47% Functional 8% Other issues 5% Practices 9% Maintenance 1% Human Error 14% 14
High accident potential unforgiving conditions No formal Ad-hoc Heightened safety accommodate human error Generic Formal Road factors 43% 14% 4% 1,5% 25% 19% Heightened safety accommodate human error 3% Human error and nonstandard acts 47% 1,5% Vehicle mechanical and 'other' factors 10% 15
Mine Haul Road Safety Audits The objectives of using a safety audit systems are; To provide a structured appraisal of potential safety problems for road-users and road operators To ensure that suitable measures for the problem elimination are fully evaluated and applied Mine Haul Road Safety Audits The benefits of using a safety audit systems are; A potential reduction in the number and severity of T&M accidents Haul road safety is given greater prominence in the minds of road-user, operators and ers The need for costly remedial work is reduced (if the audit is implemented at the stage) 16
Mine Haul Road Safety Audits Audit Stage Feasibility Design Component Assessed General Topics General Design Issues Alignment Junctions Environmental Road Users Mine Haul Road Safety Audits Audit Stage Draft Design Design Component Assessed General Topics General Design Issues Alignment Junctions Environmental Road Users Signs and lighting Other 17
Mine Haul Road Safety Audits Audit Stage Detailed Design Design Component Assessed General Topics General Design Issues Alignment and cross section Junctions Environmental Road Users Signs and lighting Physical Objects Construction Other Mine Haul Road Safety Audits Audit Stage Pre-Opening Design Component Assessed General Topics General Design Issues Alignment and cross section Junctions Road Users Signs and lighting Physical Objects Maintenance Finishing Training road-users Other 18
Mine Haul Road Safety Audits Audit Stage Existing roads Design Component Assessed General Topics General Design Issues Alignment and cross section Junctions Road Users Signs and lighting Physical Objects Maintenance Training road-users Road-user feedback 19
Practical Applications ID the KPS Key Performance Segments on your road network; Safety-critical segments intersections, ramps, switchbacks, etc. High speed high tonnage roads Prioritize remediation on these segments Practical Applications Visual inspections mark roads where maintenance should be done with red, yellow or green cones prioritize. Record maintenance intervention (what done) and frequencies (how often) per segment establish a rehabilitation schedule prioritize BUT. 20
Practical Applications Why does the segment have safety-critical issues? Poor and / or build specs; Geometrics Structure (layer works and materials) Functional (wearing course) Investigate the root-cause of the under- performance before deciding on a remediation strategy Conclusions The Problem Poor or no haul- and roadway often leads to otherwise avoidable T&M accidents 21
Conclusions The Challenge How to a haul- or roadway that is more accommodating for driver error? How to benchmark the suitability of existing roads? How to remediate haul road problems? Conclusions The Way Ahead Training mine staff in the principles of good road The use of more formal geometric and functional procedures to assist in eliminating accidents The use of a haul road audit system to evaluate proposed or current road and safety performance 22
Conclusions Additional Resources Technology www.advminingtech.com.au www.acumine.com http://jnbqp1.corporate.aaplc.com/hme (by invitation) Road guidelines and performance benchmarking www.up.ac.za/academic/mining/research/research_frame.htm Road and management training courses www.ceatup.com Acknowledgements Parts of the work described in this paper was carried out as part t of the other mines research program of the Mine Health and Safety Council Safety in Mines Research Advisory Committee. The authors gratefully acknowledge the financial assistance and support received from the SIMRAC and SIMOT committees. Details may be found from; www.simrac.co.za/report/reports/thrust5/oth308/oth308.htm. 23