Table of Contents

Acknowledgements
1    OBJECTIVE AND METHODICS OF THIS THESIS
1.1  PREFACE
1.2  THE EVALUATION OF THE CURRENT POSITION
1.3  THE NAMIBIAN ROADS MODEL OF THE FUTURE
2     DEVELOPMENT OF A ROADS SYSTEM 1965 TO DATE
2.1  PLANNING TO DATE
2.2  PRESENT SITUATION OF THE ROADS SYSTEM
2.3  STRUCTURAL DEVELOPMENT OF PAVEMENTS AND EXPERIENCES
2.4  FUTURE DEVELOPMENT
3    ENVIRONMENTAL INFLUENCES ON ROAD BUILDING
3.1  CLIMATE IN NAMIBIA
3.2  FLOOD CALCULATIONS FOR NAMIBIAN CONDITIONS
3.3  OCCURRENCE OF NATURAL ROAD BUILDING MATERIALS
4    THE LOCATION AND PROPERTIES OF ROAD BUILDING MATERIALS
4.1    THE VAALIAN AGE
4.2    THE MOKOLIAN AGE
4.2.1 KHOABENDUS GROUP
4.2.2 THE REHOBOTH AND SINCLAIR SEQUENCES

4.3   THE NAMIBIAN AND CAMBRIAN AGES
4.3.1 DAMARA SEQUENCE: NORTHERN ZONE
4.3.2 DAMARA SEQUENCE: CENTRAL ZONE
4.3.3 DAMARA SEQUENCE: SOUTHERN ZONE
4.3.4 THE GARIEP COMPLEX
4.3.5 THE NAMA GROUP

4.4    THE KAROO SEQUENCE
4.4.1 TILLITE AND OTHER STRATA OF THE DWYKA FORMATION
4.4.2 KAROO SANDSTONES AND MUDROCKS
4.4.3 VOLCANIC ROCKS OF THE KAROO SEQUENCE
4.4.4 KAROO DOLERITE
4.5   THE TERTIARY TO QUATERNARY AGES: KALAHARI SEQUENCE

4.6   SAND AS IMPORTANT NAMIBIAN ROAD BUILDING MATERIAL
4.6.1 COASTAL DEPOSITS FROM TERTIARY TO RECENT
4.6.2 INTERIOR DEPOSITS FROM TERTIARY TO RECENT
4.7   THE USE OF PEDOCRETES IN NAMIBIA
5      THE DEVELOPMENT OF VEHICLE OPERATING COSTS FOR NAMIBIA
5.1.   INTRODUCTORY REMARKS
5.2    THE DEVELOPMENT OF 'VOC' INVESTIGATIONS
5.3    THE SOUTH AFRICAN 'VOC' STUDY
5.3.1  QUANTIFIABLE ELEMENTS OF THE SOUTH AFRICAN STUDY
5.3.1.1  FUEL RELATIONSHIPS
5.3.1.2  TYRE RELATIONSHIPS
5.3.1.3  VEHICLE MAINTENANCE RELATIONSHIPS
5.3.1.4  VEHICLE DEPRECIATION RELATIONSHIPS
5.3.2 RESULTS OF THE SOUTH AFRICAN 'VOC' STUDY
5.3.3 THE NAMIBIAN 'VOC' STUDY
5.3.3.1  ROAD TEST SECTIONS
5.3.3.2  TEST VEHICLE
5.3.3.3 ANALYSIS OF RESULTS
5.3.4 COMPARISON BETWEEN NAMIBIAN AND HDM 3 'VOC' STUDIES
6      A COST AND QUALITY OPTIMISED MODEL FOR PAVED ROADS
6.1    NAMIBIA'S BUDGETARY MAINTENANCE PREDICAMENT
6.2    VISUAL-SENSITIVE METHODS TO SOLVE THE PROBLEM
6.2.1 VISUAL SURVEYS
6.3    THE FIRST NAMIBIAN RESEAL ALGORITHM
6.4    REVISED PROPOSALS FOR A RESEAL ALGORITHM
6.4.1 REVISED VISUAL SURVEYS AND SERIOUS RATINGS
6.4.2 PROPOSED NEW RESEAL ALGORITHM
6.5    STRUCTURAL ASPECTS OF PAVEMENTS
6.5.1 STRUCTURE OF PAVEMENTS OF PAVED ROADS
6.6   RESULTS OF THE PERFORMANCE MODEL STRUCTURE
6.7   THE RELATIONSHIP BETWEEN 'VOC' AND 'PMS'
6.8   PROPOSAL FOR A RELAXED MATERIALS SPECIFICATION
7      A COST AND QUALITY OPTIMISED MODEL FOR UNPAVED ROADS
7.1   DESIGN AND MAINTENANCE CRITERIA
7.1.1 INTRODUCTORY REMARKS
7.1.2 PROBLEM IDENTIFICATION
7.2   RESULTANT LEVEL OF SERVICE
7.3   PREDICTING UNPAVED ROAD PERFORMANCE
7.3.1 DRY WEATHER DETERIORATION
7.3.2 GENERAL WET WEATHER DETERIORATION
7.3.3 WET WEATHER DETERIORATION FOR WEAK ROADS
7.3.4 EVALUATION OF EMPIRICAL STUDIES
7.3.5 PREDICTION FOR COST/QUALITY OPTIMISED MODELS
7.3.5.1 PREDICTION MODEL FOR ROUGHNESS
7.3.5.2 PREDICTION MODEL FOR GRAVEL LOSSES
7.3.6 PREDICTION EQUATIONS FOR GENERAL PERFORMANCE
7.3.6.1 PREDICTION MODEL FOR RUT DEPTH
7.3.6.2 PREDICTION MODEL FOR CORRUGATIONS
7.3.6.3 PREDICTION MODEL FOR DUST
7.3.6.4 PREDICTION MODEL FOR POT-HOLES
7.3.6.5 PREDICTION MODEL FOR CRACKS
7.3.6.6 PREDICTION MODEL FOR SMALL STONES
7.3.6.7 PREDICTION MODEL FOR SURFACE DRAINAGE
7.3.7 GENERAL PERFORMANCE WITHOUT PREDICTION MODELS
7.3.7.1 LARGE STONES
7.3.7.2 SKID RESISTANCE

7.4    OPTIMAL MATERIALS SPECIFICATION
7.4.1 NORMAL GRAVEL AND EARTH ROADS
7.4.2 ATLANTIC COAST SALT-GRAVEL ROADS
7.4.3 THE MATERIAL SPECIFICATION FOR UNPAVED ROADS
7.5    COST AND QUALITY OPTIMISED MODELS
7.5.1 DETERMINATION OF OPTIMAL GRADING FREQUENCIES
7.5.2 DETERMINATION OF OPTIMAL GRAVELLING FREQUENCIES
7.5.3 DETERMINATION OF THE OPTIMAL SURFACING POINT
8      TECHNICAL ASPECTS OF APPROPRIATE LOW-VOLUME ROADS
8.1    GENERAL APPROACH
8.2    PERFORMANCE OF LOW-VOLUME AND LOW-COST ROADS
8.2.1 DESIGN STANDARDS FOR ROAD PAVEMENTS
8.3    DISCUSSION OF A PROPOSED SYSTEM OF LOW-VOLUME ROADS
8.3.1 CLASS A LOW-VOLUME ROADS: EARTH ROADS
8.3.1.1 DESIGN CONSIDERATIONS
8.3.1.1.1 GEOMETRICAL DESIGN PARAMETERS
8.3.1.1.2 STRUCTURAL DESIGN PARAMETERS
8.3.1.2 CONSTRUCTION CONSIDERATIONS
8.3.1.3 MAINTENANCE CONSIDERATIONS
8.3.2 CLASS B LOW-VOLUME-ROADS: GRAVEL ROADS
8.3.2.1 DESIGN CONSIDERATIONS
8.3.2.1.1 GEOMETRICAL DESIGN PARAMETERS
8.3.2.1.2 STRUCTURAL DESIGN PARAMETERS
8.3.2.2 CONSTRUCTION CONSIDERATIONS
8.3.2.3 MAINTENANCE CONSIDERATIONS
8.3.3 CLASS C: LOW-COST ROADS WITH BITUMEN PAVING

8.3.3.1 DESIGN CONSIDERATIONS
8.3.3.1.1 GEOMETRICAL DESIGN PARAMETERS
8.3.3.1.2 STRUCTURAL DESIGN PARAMETERS
8.3.3.2 CONSTRUCTION CONSIDERATIONS
8.3.3.2.1 BITUMINOUS BINDERS
8.3.3.2.2 TYPE OF AGGREGATES
8.3.3.2.3 SEAL TYPES
8.3.3.3 MAINTENANCE CONSIDERATIONS
8.3.4 CLASS D: LOW-COST ROADS WITH CONCRETE PAVINGS
8.3.4.1 DESIGN CONSIDERATIONS
8.3.4.1.1 GEOMETRICAL DESIGN PARAMETERS
8.3.4.1.2 STRUCTURAL DESIGN PARAMETERS
8.3.4.2 CONSTRUCTION CONSIDERATIONS
8.3.4.2.1 CONSTRUCTION POINTS
8.3.4.2.2 MANUFACTURE OF "SPOORBAAN" BLOCKS
8.3.4.2.3 ESTABLISHMENT
8.3.4.2.4 LABOUR
8.3.4.2.5 RAW MATERIALS
8.3.4.2.6 TRANSPORT
8.3.4.2.7 CONSTRUCTION OF THE SPOORBAAN ROAD
8.3.4.3 MAINTENANCE CONSIDERATIONS
8.3.5 FIRST EXPERIENCES WITH SPOORBAAN TEST
8.3.5.1 OBJECTIVE OF THE TEST SECTION

8.3.5.2 IMPLEMENTATION OF THE TEST SECTION
8.3.5.3 EVALUATION OF PERFORMANCE
8.3.5.3.1 EXPERIENCES WITH SECTION 1
8.3.5.3.2 EXPERIENCES WITH SECTION 2
8.3.5.3.3 EXPERIENCES WITH SECTION 3
8.3.5.3.4 EXPERIENCES WITH SECTION 4
8.3.5.4 CRITICAL ASSESSMENT OF THE TEST
8.3.5.5 RECOMMENDATIONS FOR A SPECIFICATION
8.3.5.6 FURTHER CLASS D ROAD CONSIDERATIONS
8.3.5.6.1 SUB-SURFACE MEMBRANES AND MATRICES
8.3.5.6.2 STABILISATION WITH FOAMED BITUMEN
8.3.5.6.3 PERFORMANCE OF SALT-GRAVEL ROADS
8.3.6 A CASE FOR LABOUR-BASED METHODS
9      CONCLUSION AND SUMMARY
10     USED LITERATURE
11     APPENDICES
        APPENDIX 1 LIST OF IMPORTANT ABBREVIATIONS

        APPENDIX TABLE 1: FUEL CONSUMPTION ON PAVED ROADS
        APPENDIX TABLE 2: FUEL CONSUMPTION ON UNPAVED ROADS
        APPEMDIX MAP 1: MAJOR TRUNK AND MAIN ROADS
        APPENDIX MAP 2: TRAFFIC VOLUMES
        APPENDIX MAP 3: NATURALLY OCCURRING BUILDING MATERIALS
        APPENDIX MAP 4 GEOLOGY OF NAMIBIA
        APPENDIX SKETCH 1: TYPICAL SECTION OF SPOORBAAN STRIP ROAD
        APPENDIX SKETCH 2:  DIMENSIONS OF SPOORBAAN BLOCK
TABLES

TABLE 1 STATUS OF NATIONAL ROADS: ODENDAAL COMMISSION
TABLE 2 NAMIBIA: ROAD NETWORK BY ROAD CATEGORIES (km)
TABLE 3 GEOGRAPHICAL DISTRIBUTION OF VARIOUS ROAD CLASSES
TABLE 4 NAMIBIA: THE ROADS SYSTEM ON A DISTRICT BASIS, 1986
TABLE 5 VEHICLE NUMBERS IN NAMIBIA ACCORDING TO THEIR TYPES
TABLE 6 NAMIBIA: ROADS ACCORDING TO THEIR PAVEMENT TYPES
TABLE 7 DEVELOPMENT OF PAVEMENTS FOR PAVED ROADS: 1957-1985
TABLE 8 RUN-OFF COEFFICIENTS: RATIONAL FORMULA: D.o.T.
TABLE 9 MEAN ANNUAL PRECIPITATION FOR 35 RAINFALL STATIONS

TABLE 10 ROAD BUILDING MATERIALS IN NAMIBIA: ROCKS AND STONES
TABLE 11 ROAD BUILDING MATERIALS IN NAMIBIA: SAND

TABLE 12 LOCATION AND PROPERTIES OF VAALIAN AND MOKOLIAN ROCKS
TABLE 13 PHYSICAL PROPERTIES OF QUARRIED DOLOMITE: OTAVI GROUP
TABLE 14 ROAD-BUILDING PROPERTIES OF WEATHERED MULDEN PHYLLITE
TABLE 15 ROAD BUILDING PROPERTIES OF WEATHERED SALEM GRANITE
TABLE 16 LOCATION AND PROPERTIES: NAMIBIAN AND CAMBRIAN ROCKS
TABLE 17 LOCATION AND PROPERTIES OF KAROO ROCKS
TABLE 18 LOCATION/PROPERTIES OF TERTIARY AND QUATERNARY ROCKS

TABLE 19 TYPICAL CHEMICAL COMPOSITIONS OF PEDOCRETES
TABLE 20 RECOGNITION OF PROBLEM PEDOCRETES

TABLE 21 SURVEY DATA FOR 'VOC' MAIN STUDIES
TABLE 22 HDM3 PREDICTION OF 'VOC' FOR A MEDIUM TRUCK: PAVED ROAD
TABLE 23 QUANTIFIABLE ELEMENTS OF ROAD USER COSTS
TABLE 24 THE EFFECT OF ROAD ROUGHNESS ON FUEL CONSUMPTION
TABLE 25 VEHICLE OPERATING COSTS FOR A PASSENGER BUS
TABLE 26 VEHICLE OPERATING COSTS FOR A PASSENGER CAR
TABLE 27 VEHICLE OPERATING COSTS FOR A MEDIUM TRUCK

TABLE 28 SERIOUSNESS RATING FOR CRACKING
TABLE 29 SERIOUSNESS RATING: SURFACING AGGREGATE AND BLEEDING
TABLE 30 SERIOUSNESS RATING FOR CRACKING: REVISED METHOD
TABLE 31 SERIOUSNESS RATING: SURFACING AGGREGATE AND BLEEDING
TABLE 32 PREDICTED SAVINGS IN 'VOC' FOR PAVED ROADS

TABLE 33 MAINTENANCE PARAMETERS OF SOME UNPAVED ROADS
TABLE 34 SUBJECTIVE RIDING QUALITY AS FUNCTION OF ROUGHNESS
TABLE 35 CONTRIBUTION FACTORS TO POOR RIDING QUALITY
TABLE 36 PERFORMANCE CRITERIA FOR UNPAVED ROADS
TABLE 37 UNPAVED ROAD SECTIONS FOR NAMIBIAN 'MDS' SYSTEM
TABLE 38 RIDING QUALITIES STATISTICS OF SAMPLE SOURCES
TABLE 39 MATERIAL PROPERTIES STATISTICS
TABLE 40 MATERIALS SPECIFICATION FOR GRAVEL WEARING COURSES

TABLE 41 SPOORBAAN EXPERIMENTAL SECTION: BASIC PARAMETERS
TABLE 42 SPOORBAAN EXPERIMENTAL SECTION: OSHANA REGION
TABLE 43 DESIGN PARAMETERS: SECTION 2: SPOORBAAN EXPERIMENT
TABLE 44 LOWER COST ACTIVITIES: LABOUR AGAINST EQUIPMENT

FIGURES

FIGURE 1 GRADINGS OF TYPICAL NAMIB AND KALAHARI SANDS
FIGURE 2 VEHICLE OPERATING COSTS: FUEL: SURFACED PAVEMENTS
FIGURE 3 VEHICLE OPERATING COSTS: FUEL: UNPAVED ROADS
FIGURE 4 COMPARISON OF 'VOC' FOR RSA/NAMIBIAN AND HDM 3
FIGURE 5 JUDGEMENT OF PAVEMENT DEFECTS
FIGURE 6 APPROPRIATENESS OF A RESEAL
FIGURE 7 REVISED RESEAL ALGORITHM
FIGURE 8 NAMIBIAN MAINTENANCE DESIGN SYSTEM
FIGURE 9 ACCEPTABILITY CRITERIA AS FUNCTION OF ROAD ROUGHNESS
FIGURE 10 INTERACTION OF PAVEMENT DETERIORATION MODES
FIGURE 11 PREDICTION: ROUGHNESS CHANGE AS FUNCTION OF 'ADT'
FIGURE 12 PREDICTION: GRAVEL LOSS AS FUNCTION OF 'ADT'
FIGURE 13 PREDICTION: RUT DEPTH AS FUNCTION OF 'ADT'
FIGURE 14 OPTIMAL POINT OF GRADING OF UNPAVED ROADS
FIGURE 15 OPTIMAL POINT OF SURFACING UNPAVED ROADS
FIGURE 16 RIDING QUALITY RESULTS: SPOORBAAN TRIAL: D.R.3613
FIGURE 17 APPROPRIATENESS OF LABOUR-BASED ACTIVITIES 206

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