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Paper and Presentation for the DME Open Pit Safety Workshop

December 7th 2006 Witbank, Mpumulanga Province, South Africa

Designing and benchmarking mine roads for safe and efficient hauling

R J Thompson Professor

Department of Mining Engineering University of Pretoria

PRETORIA 0002 South Africa

A T Visser SA Roads Board Professor of Transportation Engineering

Department of Civil Engineering University of Pretoria

PRETORIA 0002 South Africa

Tel 012 420 3195 Fax 012 420 4242 E-mail roger.thompson@ up.ac.za

Designing and benchmarking mine roads 1 Thompson, RJ & Visser, AT for safe and efficient hauling DME Open-Pit Safety Workshop, Witbank, 7th Dec 2006

Designing and benchmarking mine roads for safe and efficient hauling

Abstract Mining in South Africa often employs free-steered vehicles running on haul- or road-ways for the transport of rock from the excavation faces to the loading, transfer or dump point. This accomplished by haul trucks, load-haul-dumpers and/or service vehicles running on unpaved haul roads that have, at best, been empirically designed, often with little or no recognition of the consequences of inadequate design on health and safety. In transport-related accidents and incidents, if adequate and benchmarkable standards were established, some of the typical accidents encountered could be reduced by providing greater accommodation of error, or reducing the inherent potential and hazards associated with transport operations. This paper and presentation focuses on industry ‘best-practice’ design and benchmarks applicable to road design in the mining industry. In addition to highlighting the various design standards of road geometrics, structural, functional and maintenance aspects, the presentation also introduces a safety audit approach in which a number of key design components are recognised and audit benchmarks established. The benefits of the approach are seen as a basis for reducing the potential of an under-designed mine road to lead to accidents and secondly as a means of giving haul road safety issues greater prominence in the minds of the road-user, operator, mine planner and designer alike.

Introduction Transport and tramming operations on mines are an area of considerable accident risk, 51 percent of accidents, 30 percent of fatalities and 48 percent of injuries on mines were associated with transport and tramming machinery and mining (T&M) operations1. Seventy-four percent of these accidents on surface mines were associated with ore transfer by haul truck and service vehicle operation2. For underground mines, ore transfer by load-haul-dumper and service vehicle operation represented 56 percent of the potential active failures observed.

To what extent is haul road design – or lack of – a contributory factor? The haul road design forms a principal component of a transport and tramming operation on both surface and underground mines. The effect or impact of haul road design, construction and maintenance practices on safety and health is not well defined at present. However, most mine operators agree that a strong relationship exists between well constructed and maintained roads and safe, efficient mining operations. Large modern surface mining operations in which extensive use is made of free-steered vehicles operating on unpaved roads generally incorporate high standards of road design work into the overall mine plan. The result is usually a well constructed roadway that is safe to operate and easy to maintain. This situation can be quite different for smaller surface or underground mining operations where either only a few vehicles are used in the transport of material or traffic volumes are comparatively low. Larger operations usually exhibit and stronger and more well-defined management philosophy in which special localised consideration is often given to haul road construction and maintenance, whereas smaller operations, by virtue of their size, generally operate without such extensive management. The design and management of mine haul roads encompasses geometric, structural, functional (wearing course), and maintenance categories. These are defined3 as;

Geometric design. This refers to the layout and alignment of the road, in both the horizontal (curve radius, etc.) and vertical (incline, decline, ramp gradients, cross-fall, camber, super-elevation) plane, stopping distances, sight distances, junction layout, berm walls, provision of shoulders and road width variation and should accommodate optimal vehicle speeds, stability, road performance and safety.

Structural design. This concerns the ability of a haul road to carry the imposed loads without excessive pavement deformation and consequently the need for excessive maintenance.


Functional design. This refers to the ability of the haul road to perform its function, i.e. to provide an economic, safe and vehicle friendly ride. The selection and management of wearing course materials (or surfacing) primarily controls the functional performance.

Maintenance design. The management and scheduling of maintenance (blading, watering and regravelling) of the wearing course according to the limits of the expected and actual road performance.

A literature review encompassing these design categories in conjunction with free-steered vehicles operating on unpaved surface or underground mine haul roads revealed considerable information outlining good operational and construction practices4, 5, 6, albeit without any definite correlation to safety or accident impacts. No data was reported on the precise contribution of poor structural design work on the incidence of accidents, other than in terms of an overall increase in vehicle operating and road maintenance costs. Similar data limitations were seen in respect of functional design. Although an abundance of information on the geometric design of roads was found, again, scant attention was paid to the role of poor design in transportation accidents, suffice to say that whilst the cost of applying the correct design criteria is often excessive to the operator, the benefits therefrom, in terms of improved transportation safety, were often impossible to determine since they were hidden in such intangible factors as reduced accidents and injuries. Benefits, in terms of improved productivity – cost per unit hauled – is however much easier to asses when improved design techniques are used. A well designed road is often COST effective as well as SAFE to operate This paper briefly presents an analysis of transport related accidents and shows how poor road design is often implicated. Using the critical road design deficiencies identified, a mine haul road safety audit system is proposed. The adoption of the mine haul road safety audit system is recommended as a means to attaining a reduction in accidents through the structured recognition and assessment of haulage hazards and the application of optimally safe designs for mine haul- and roadways.

T&M Accidents In Surface And Underground Mining The SAMRASS data-base gives an overview of accidents in the South African mining industry. Approximately 20 percent of total accidents recorded are classified as T&M accidents. Figure 1 summarises the information based on the attributable reportable accident rate per 1000 persons per class of mine.

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Transport and Mining Accidents

Percentage of total attributable T&M accidents per 1000 persons per mine type

Percentage T&M accidents of total accidents reported

Percentage T&M accidents per mine type attributable to vehicles on mine haul or roadways

Figure 1 Transport and mining (T&M) typical percentages of total attributable accident rate/1000 persons per mine type

Higher accident rates (per 1000 workers) were seen to be associated with copper, iron, granite, limestone and clay mining operations which, although not reporting a large number of attributable accidents per year, exhibited higher than average accident rates. Between 20-30 percent of the total attributable accident rate is derived from


these classes of mine. When the data was split according to the type of operation (surface or underground), a similar trend was seen, with consistently high percentage contributions of iron, granite, limestone and clay surface mining operations.

What sub-standard ACTS or CONDITIONS lead to these high accident rates? The attributable accident records were further analysed to determine the sub-standard act or condition which either led to, or was implicated in each attributable accident. Table 1 shows the criteria used in the assessment where the agency involved is initially identified (either sub-standard acts or conditions). Once the agency is identified, the specific action or condition implicated is identified. Table 2 summarises the principal deficient road design factors thus determined, whilst Figure 2 presents the various percentages of agency factors implicated in these attributable accidents.

Table 1 Classification system adopted to determine T&M attributable accident causes

ACCIDENT AGENCY

Sub-standard acts

Sub-standard conditions

Road design factor

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Percentage of road design factors implicated in attributable T&M accidents

Maintenance1%

Road design related accidents

47%

Other issues5%

Not attributable53%

Practices9%

Functional8%

Geometric10%

Human Error14%

Figure 2 Role of road design in T&M attributable accidents

Of the total T&M accidents analysed and categorised, 53 percent were found not to be attributable to acts or conditions listed in Table 1. Of the 47 percent attributable, 57 percent were associated with non-standard acts including human error. Of the 43 percent associated with sub-standard road design factors, geometric and functional components predominate as the agencies implicated, with maintenance and structural design


exhibiting very little influence. From an analysis of the principal sub-standard surface mine road design factors which were most frequently encountered in the accident reports, the primary areas of concern were the functional factors of dustiness, poor visibility, skid resistance and large stones in or on the road. In the case of geometric design it was seen that inappropriate junction layout, the absence of safety berms and lack of a road shoulder area were most frequently cited as factors in sub-standard geometric design. Table 2 Summary of principle deficient surface mine road design factors

Functional Design

Geometric Design

Dustiness Wearing course material selection inappropriate

Junction layout Poor junction layout or incorrect or inappropriate signage. Poor visibility of or from junction.

Poor visibility Excessive dustiness generated from vehicle wind shear or due to windy conditions, especially at night

Safety berms No safety berms where road runs on an embankment (fill area) or berms too small. Vehicles which lost control on these sections ran off the road.

Skid resistance Wet wearing course material, either after rain or watering to allay dust. In several instances, dry skid resistance also problematic.

Road shoulders Collisions with vehicles (breakdown, etc.) parked on roadside, no shoulder or road too narrow.

Large stones LDV's or smaller utility vehicles running over large stones protruding from the wearing course. Spillage from trucks is also a common causative factor.

Run-aways- brakes Accidents due to brake failures whilst hauling laden down-grade or vehicle run-aways down-grade. Excessive gradients (>10%).

In the majority of accident reports analysed, scant attention or recognition was given to basic road design components, even where the deficient condition which led directly to the accident was clearly stated. Figure 3 shows how the type of design activity relates to attributable accident rate (T&M accidents that involved vehicles on mine haul or roadways). It is seen that the more ‘formal’ a design activity is, the less is the attributable accident rate.

Correlation between formal haul road design activities and T&M accident rates

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Percentage attributable T&M accidents / 1000 workers

Functional design methodsGeometric design methodsTrend for Geometric DesignsTrend for Functional Designs

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No design methods

Figure 3 Relationship between how well the road is designed and the attributable T&M accident rates

Solutions to mine haul road safety problems are mostly physical in nature since they relate to the road design components of geometry and function mostly. However, this work has shown that human factors (including non-standard practices), vehicle (mechanical) factors and deficiencies in road design are all implicated in attributable


accidents. Figure 4 illustrates the relative percentage contributions of each of these factors to attributable T&M accidents.

Human error and non-standard acts 47%

Road design factors 43%

Vehicle mechanical and 'other' factors

19%

25%

14%3%

1,5%4%

1,5%

Figure 4 Factors interactions contributing to T&M attributable accidents

Whilst improved mine haul road design activities may well reduce design-related accidents, it would appear that little recognition is given to the human factors which are present in attributable T&M accidents to the greatest extent.

The human factor is the most problematic to address in a road design. It is often easier break the link between the interactive effects which may lead to accidents than trying to predict and reduce human error

These human factor interactive effects include the structural, functional, maintenance and geometric design components and from Figure 4 it is seen that 25 percent of the attributable accidents in which human error was implicated were also associated with deficiencies in road design. To prevent an accident or reduce the severity of its consequences, a road should be more accommodating to human error. In this way a haul road can be designed to compensate for human error; the more that is known about human error, the better the road can be designed to accommodate those actions or non-standard practices. A typical illustration of this approach is to consider the many accidents caused by drivers falling asleep at the wheel. Rather than directly address the problem detecting drowsiness, it is often easier to design a road that will warn the driver, by deflecting the vehicle away from danger and/or preventing vehicles from running in to each other or off the road by using centreline and crest berms.

Mine Haul Road Safety Audit System In the analysis of T&M accidents and in particular those attributable to road design factors it was found that although only a small percentage of such accidents are directly attributable to poor design standards, there was a general lack of recognition of the role of the various design factors in safe transportation operations. A haul road safety audit can be defined as7;

‘A formal examination of an existing or proposed haul road which interacts with the road-users, in which an examiner reports on the road or project accident potential and safety performance’.

In the light results of the foregoing analyses, the objectives of conducting a haul road safety audit may be summarised as;


o To provide a structured appraisal of potential safety problems for road-users and road operators alike

o To provide a structured appraisal of potential safety problems for road-users and road operators alike

o To ensure that suitable measures safety problem elimination are fully evaluated and applied o To ensure that suitable measures safety problem elimination are fully evaluated and applied whilst the benefits are seen as; whilst the benefits are seen as;

o A potential reduction in the number and severity of T&M accidents o A potential reduction in the number and severity of T&M accidents

o Haul road safety is given greater prominence in the minds of road-user, operators and designers

o Haul road safety is given greater prominence in the minds of road-user, operators and designers

o The need for costly remedial work is reduced (if the audit is implemented at the design stage)

o The need for costly remedial work is reduced (if the audit is implemented at the design stage)

A mine haul road safety audit can be conducted on any existing haul road, surface or underground, or on any proposal which is likely to alter the interactions between different road-users (i.e. haul trucks, service vehicles, maintenance equipment and the road), or between road-users and their physical environment. Its purpose is to consider the accident potential and safety performance of the road or proposal using a formal structured appraisal of a number of defined design category factors. Through the use and adoption of such an audit scheme, mine personnel will become conversant with the various haulage safety hazards associated with poor design and this will enable operators to more readily evaluate the safety risks generated by existing or proposed modifications to a particular haul road or section of road.

A mine haul road safety audit can be conducted on any existing haul road, surface or underground, or on any proposal which is likely to alter the interactions between different road-users (i.e. haul trucks, service vehicles, maintenance equipment and the road), or between road-users and their physical environment. Its purpose is to consider the accident potential and safety performance of the road or proposal using a formal structured appraisal of a number of defined design category factors. Through the use and adoption of such an audit scheme, mine personnel will become conversant with the various haulage safety hazards associated with poor design and this will enable operators to more readily evaluate the safety risks generated by existing or proposed modifications to a particular haul road or section of road. Stages and components of a haul road safety audit Stages and components of a haul road safety audit The approach to haul road safety auditing is based on the application of the technique at the earliest possible stage of the project, thereby ensuring early elimination of any potential safety problems. It is recognised that the technique should also be applicable to existing roads to enable operators to identify potential safety problems and take appropriate steps to rectify them. Thus five stages are involved;

The approach to haul road safety auditing is based on the application of the technique at the earliest possible stage of the project, thereby ensuring early elimination of any potential safety problems. It is recognised that the technique should also be applicable to existing roads to enable operators to identify potential safety problems and take appropriate steps to rectify them. Thus five stages are involved; 1 The feasibility stage 1 The feasibility stage 2 The draft design stage 2 The draft design stage 3 The detailed design stage 3 The detailed design stage 4 The pre-opening stage 4 The pre-opening stage 5 The audit of existing haul roads 5 The audit of existing haul roads For each stage the components of structural, functional, maintenance and geometric design are assessed according to a number of design factor issues for each component. The scope of the design factor issues increases as the design process becomes finalised, the most comprehensive list of issues being associated with the audit of existing haul roads. Table 3 illustrates the breakdown of audit stages and design components.

For each stage the components of structural, functional, maintenance and geometric design are assessed according to a number of design factor issues for each component. The scope of the design factor issues increases as the design process becomes finalised, the most comprehensive list of issues being associated with the audit of existing haul roads. Table 3 illustrates the breakdown of audit stages and design components.

1 2 3 4 54 5AUDIT STAGE FEASIBILITY DRAFT

DESIGN DETAILED

DESIGN PRE-OPENING EXISTING

Des

ign

com

pone

nts

General Topics General Design Issues Alignment Junctions Environmental Road Users

General Topics General Design Issues Alignment Junctions Environmental Road Users Signs and lighting Other

General Topics General Design Issues Alignment and cross section Junctions Environmental Road Users Signs and lighting Physical Objects Construction Other

General Topics General Design Issues Alignment and cross section Junctions Road Users Signs and lighting Physical Objects Maintenance Finishing Training road-users Other

General Topics General Design Issues Alignment and cross section Junctions Road Users Signs and lighting Physical Objects Maintenance Training road-users Road-user feedback

Table 3 Mine haul road design safety audit components

The first four checklists are most usefully applied consecutively during a road design project. The checklist compiled for existing roads may be used as a guide to the efficacy of an established design and as an aid in recognising specific transportation and haul road hazards. This should ideally be carried out when some modification to the haul road network, traffic volumes or vehicle types are made.


The safety audit approach is based on the recognition and systematic auditing of a number of key design components and issues. The benefits of the approach, in the light of the findings relating to the role of road design in T&M accidents are seen as a potential reduction in the number and severity of T&M accidents and secondly, haul road safety is given greater prominence in the minds of the road-user, operator and designer alike. Appendix 1 contains the audit checklists for existing roads, and the full audit checklists can be found on the Mine Health and Safety Council (SIMRAC) web-site8.

Conclusions Although the contribution to total mine accidents from inadequate road design is relatively small, it is nevertheless a significant source of accidents in a number of specific types of mining, especially surface limestone, dimension stone, chrome, iron and sand and clay. There is also clear evidence to suggest that there is no formal recognition of road design requirements in many of these operations. A formal checklist of road design components would enable mine operators to focus on the particular design deficiency identified in the accident and improve or modify that design component accordingly. It was also argued that of those accidents in which human error or non-standard practices were implicated, if adequate road design standards were generally in use, some of these types of accidents could have been avoided by providing greater accommodation of error, or reducing the inherent error potential and hazards associated with transportation operations. A mine haul road safety audit system was developed to improve awareness of the role of good design in reducing transportation accidents. The safety audit approach was based on the recognition and systematic auditing of a number of key design components and issues. The benefits of the approach, in the light of the findings relating to the role of road design in T&M accidents are seen as a potential reduction in the number and severity of T&M accidents and secondly, haul road safety is given greater prominence in the minds of the road-user, operator and designer alike. Acknowledgements The work described in this paper was carried out as part 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. References 1 PHILLIPS, H.R. & LANDMAN, G. 1995. Safety in Mines Research Advisory Committee, Collieries Sub-committee final project

report COL034, Department of Minerals and Energy, Pretoria, South Africa. 2 SIMPSON, G.C, RUSHWORTH, A.M, VON GLEHN, F.H. AND LOMAS, R.H. 1996. Investigation into the causes of transport and

tramming accidents on mines other than coal, gold and platinum. Safety in Mines Research Advisory Committee, Other Mines Sub-committee final project report OTH202, Department of Minerals and Energy, Pretoria, South Africa.

3 THOMPSON, R.J. 1996. The design and management of surface mine haul roads. PhD thesis, University of Pretoria, South Africa.

4 THOMPSON, R.J. AND VISSER, A.T: ‘Towards a mechanistic structural design method for surface mine haul roads’, Jnl. South African Institution of Civil Engineering, 38, n2, Johannesburg, South Africa, 1996, pp13-21

5 KAUFMAN, W.W. & AULT, J.C: ‘The design of surface mine haul roads manual’, USDOI Information circular 8758, USBM, 1977, pp 2-7, 19-30.

6 THOMPSON, R.J. AND VISSER, A.T. The functional design of surface mine haul roads. Jnl. of the South African Institute of Mining and Metallurgy, v100, n3, May/June 2000, Johannesburg, South Africa, pp169-180.

7 AUSTROADS. 1994. Road safety audit. National Association of Road Transport and Transport Authorities of Australia, AP-30/94, Sydney, Australia.

8 MINE HEALTH AND SAFETY COUNCIL. 2006. Safety in Mines Research Advisory Committee (SIMRAC). www.simrac.co.za/report/Reports/thrust5/oth308/oth308.htm. Last accessed 18.09/2006-09-20.

Useful websites (haul truck guidance, collision avoidance and RF technology) www.advminingtech.com.auwww.acumine.comhttp://jnbqp1.corporate.aaplc.com/hme (by invitation - ) Haul road design and management publications and guidelines www.up.ac.za/academic/mining/research/research_frame.htm

http://www.simrac.co.za/report/Reports/thrust5/oth308/oth308.htm

http://www.advminingtech.com.au/

http://www.acumine.com/

http://jnbqp1.corporate.aaplc.com/hme

http://www.up.ac.za/academic/mining/research/research_frame.htm


Appendix: Audit Checklists – Stage 5 – Existing Roads

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