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Regional Seminar Proceedings 1992
SESSION 5: COMPACTION
SUMMARY Compaction of 95 % and more of maximum dry density which is normally specified for fill, sub-base is hard to achieve without equipment. The question of appropriate compaction methods remains to a certain extent unresolved. Since standard rollers are too costly and their productivity too high to be compatible with a labour-based construction unit, pedestrian rollers have been recommended. How these pedestrian rollers perform is reviewed by Htun Hlaing. Whether existing compaction specifications are appropriate for low traffic earth and gravel roads is discussed. Andreas Beusch explains how in the Kenyan Rural Access Road Programme roads were constructed to satisfactory standards without compaction equipment only using natural and traffic compaction. Dr. Kyulule presents a proposal for a research programme on compaction for labour-based road projects. I. Lightweight Compaction Equipment II. Road Performance without Compaction III. Technology Development Programme (TDP) I. LIGHTWEIGHT COMPACTION EQUIPMENT
Presented by Htun Hlaing, ILO Training Adviser labour Construction Unit, Ministry of Works, Lesotho Pedestrian vibrating rollers can be used for compaction in labour-based road works. In Ghana rollers are used for compaction in activities such as cut-to-formation, camber formation and gravelling. In formation activity the fill materials were compacterd in layers not greater than 150 mm at a time. The water content in the loose material were checked and if necessary water was applied before compaction. After formation, camber was formed using materials excavated form the side ditches and slopes. After compaction a 7 % camber was to be achieved. The compaction for camber formation and gravelling was done half-road-width at a time. This enables the traffic to move on the other half width of road. Compaction was done from the outer side of the road carriage way towards the centre of the road. The roller tracks were to overlap each other about 100 mm side to side. As a rule of thumb, any point along the carriage way should be compacted without vibrating for one pass and then with vibration for another five passes before the final pass which was done without vibrating. The moisture content before compacting should be checked and if necessary watered. Along the dege of the road compaction was done manually by hand rammers. Compaction tests were carried out and 98 % density was achieved after compacting using the above method (The Ghana standard requirement for compaction is 89 %). In The Ghana Labour-based Feeder Road Project, two types of vibratory rollers were used for compaction. First the Benford 2-60B rollers were used. After two years of use on the site, these rollers started to have frequent bradkdowns which seriously effected the progress of work. It was found to be no more economical to keep on using these rollers after two years. Due to the frequency of the breakdowns on this type of rollers it was decided to purchase a different type of rollers. As a trial Bomag BW 65 S rollers were purchased. The Bogmag BW 65 S rollers were giving problems even before they were one year old such as malfunction of the vibrating system and frequent breakage of the vee belts. Therefore, through this experience it was obvious that these types of rollers were not meant for continuous running throughout the day. Towing trailers were used for moving the rollers from one place to another but the towing trailers were low tooo for some rough terrains. The above two models of rollers can also be transported by Land Rover Pick-ups. Finally the Bomag BW 90 S which was also used in Lesotho was accepted in Ghana as the suitable model. The rollers from Lesotho do not have a common specific part that breakdown. Therefore it is difficult to say which part is the common breakdown. Most breakdowns are caused by the operator's carelessness. One important point for the supervisor is to make sure that the roller operator uses the vibration system of the roller for four passes after he has compacted without using the vibration system. The roller operators do not like to use the vibration system because the handle of the rollers get vibrated strongly effecting ease of handling the handle. This can result in roads not being compacted well. Another common carelessness is that the operators put the lubricants such as engines oil into where hydraulic fluid is to be used and vice-versa. In Lesotho the roller operators sometimes become careless that during moving/driving of the roller from one place to the other, they still keep the vibration system running causing the parts in the roller to wear out faster. Sometimes the operator will be running the equipment without checking the engine oil level.
COMPARISON OF PERFORMANCE ON PEDESTRIAN VIBRATORY ROLLERS
PROS AND CONS OF THE PEDESTRIAN VIBRATORY ROLLERS
COMPACTION TEST RESULTS
LABOUR-BASED ROADS IN GHANA
Where: moisture content is 12 % to 14 % tests conducted using sand replacement test, Ghana required standard for compaction is 98 % and gravels are well graded granual materials.
COMPACTION TEST RESULTS FOR LABOUR-BASED GRAVEL ROADS IN GHANA II. ROAD PERFORMANCE WITHOUT COMPACTION THE KENYAN EXPERIENCE Presented by Andreas Beusch, Intech Beusch + Co. Compaction in the Kenyan Rural Access Roads Programme As a programme policy no formal compaction - equipment was used in the construction of Rural Access Roads (7230 km). Gravelling was done 6 months or more after completion of construction. The natural setting of the road during at least one rainy season and compaction by traffic was considered sufficient for the type of roads under the project: RAR's are no through roads, maximal length = 10 km Design speed = 30 km/h Max. 50 VPD Main purpose is to provide all-year access Certain roughness caused by lack of controlled compaction is acceptable Special attention has to be given to continuous reshaping of the carriageway during the period between contruction and gravelling. Routine maintenance length persons are able to cope with this work (section length about 1.5 km). Sufficient material is required to form a camber crossfall of up to 10 % during construction. This allows the camber to settle to a final crossfall of approximately 5 %. Gravelling is done by dumping and spreading immediately by working away form the quarry. In this way the tractors and trailers will drive over the newly gravelled road by driging on the edge of the carriageway moving towards the centre with each trip.
Compaction in the Kenyan Minor Roads Programme The Minor Roads Programme improves classified roads of a higher grade (usually D or E class roads) with a wider carriageway and higher traffic volumes. Apart from providing all-year access, road user costs become a factor of higher importance that in the RARP. A form of simple compaction was therefore considered as wishful for the programme. Since compaction with equipment such as tractor towed dead weight rollers, self propelled vibrating rollers, etc., was considered less suitable for a labour-based programme, a steel roller which can be pulled by labourers or animals was developed. Field trials with this roller have shown the following results: The roller consists of a hollow steel drum which can be filled with water for operation and emptied for easier transport from site to site. The weight for the empty roller is 500 kg and when filled with water 1200 kg. The width of the drum is 90 cm. Compaction is done without watering. Although the moisture content of the soils compacted is usually less that the optimum moisture contect, 8 - 12 passes of the roller can achieve a density of 95 % of the Maximum Dry Density. In dry areas or on stony or sandy soils the roller is less effective. The roller can be towed by labourers or donkys or oxen.
(On gradients of more that 5 % animals are unable to restrain the roller while going downhill). NOTE: All dimensions are in milimeters. DETAILS OF PRINCIPAL COMPONENTS
III. TECHNOLOGY DEVELOPMENT PROGRAMME (TDP) LABOUR-BASED COMPACTION METHODS FOR RURAL ROADS Presented by Dr. A. L. Kyulule Faculty of Engineering, Department of Civil Engineering University of Dar es Salaam
1.0 INTRODUCTION 1.1 Background Due to lack of heavy compaction equipment, many developing countries have been forced to execute most of their road construction works on labour-based methods, this being particularly true in the rural areas. Table 1.1 gives some examples of semi-equipment and labour-based compaction methods commonly used in developing countries. Table 1.1: Semi-Equipment and Labour-Based Compaction Methods
1.2 Research Problem The research work will focus on labour-based compaction methods for rural roads. The intention is not to look at the methods that achieve 95 % to 100 % dry densities on thick pavement layers, this is already well documented. Tractor towed dead weight rollers or self propelled vibrating rollers are the minimum level of equipment required to achieve this. What is necessary is to look at the effectiveness of light animal or human towed compactors on new road construction. 1.3 Justification and Relevance of Research Although issues pertaining to labour-based compaction in developing countries have been reviewed before in various parts of the world, a systematic and analytical study has not been forthcoming. This research work is intended to fill that gap. Limitations of labour-based compaction techniques as well as appropriate field control tests will also be examined. The study will result in the selection of the most suitable compaction methods for rural roads and will greatly enhance the execution of the 'Intergrated road Programme' which Tanzania is currently undertaking. The application of the research findings in Kenya, Tanzania and Zambia is expected to result in considerable economic gain for the entire region. It is also expected that the research findings will be included in the Curriculum of the University for undergraduate studies. 1.4 Literature Survey A number of literature on labour-based compaction of rural roads will be reviewed. The main sources are experiences gained from Kenya, Ghana, Thailand, Lesotho, Botswana, Namibia and other developing countries undertaking labour-based construction of rural roads. 2.0 OBJECTIVES The research work, as introduced above, will be carried jointly between the Department of Civil Engineering at the University of Dar es Salaam and the International Labour Organisation (ILO). The objectives of the research work shall be:
3.0 METHODOLOGY The research and development work would consist of studies and investigations which will be carried out in the field as well as in the Soil Mechanics Laboratory of the University of Dar-es Salaam. The research will be divided into two main phases: PHASE 1: Field and Laboratory Tests The human-towed smooth wheel steel roller will be manufactured at the Institute of Production Innovation in Dar es Salaam. Field tests will be set up in Kisii and Nyanza Province in Kenya; Kilimanjaro and Mbeya in Tanzania; and Kasama in Northern Zambia. Figure 1 shows typical test sections to be set up at each location. Soil samples will be taken from each test area for testing and analysis in the Soil Mechanics laboratory at the University of Dar es Salaam. Gravel compacted Gravel compacted No gravel placed Gravel placed Gravel placed normally, using haulage using hand-towed yet (to be placed after immediately immediately equipment roller 6 months) and compacted & compacted by hand-towed tractor towed roller roller Formation not Formation not Formation compacted Formation Formation compacted, left for compacted left for at each of the 3 stages compacted at compacted at 6 months under traffic 6 months under traffic by hand-drawn roller each of the 3 each of the 3 stages by hand stage by drawn roller tractor-towed roller In addition to field trials using human-drawn smooth roller, the following tests will be conducted in the field: (1) Determination of moisture content (2) Determination of density using the sand replacement method (3) Determination of variation of density with depth using the TRRL penetrometer equipment. PHASE 2: Monitoring of Performance of Test Sections Test sections at the various locations will be monitored with respect to the following aspects: (a) Rutting (i.e. tyre penetration into the fill material) after a specified period. (b) General settlement pattern of the fill material after a given period. (c) Erosion patterns on fills to establish the influence of compaction using light-weight equipment on drainage. 4.0 TIME SCHEDULE The research work is expected to last for a total duration of 1.2 years. Phase 1 which involves field tests and laboratory tests is expected to last for a period of 4 months. Phase 2 which involves monitoring is expected to last for period of 9 months. Appendix 2 shows the detailed time schedules of activities. 5.0 REPORTING In the course of the research work a total of 2 reports will be submitted, i.e. one progress report at the completion of phase 1 and a final report at the completion of phase 2. 6.0 COST ESTIMATES Given below is a summary of cost estimates for the research work. The breakdown of the financial requirements can be ssen in Appendix 1. 1. Phase 1: Field and laboratory tests: TShs. 1,091,738.00 2. Phase 2: Monitoring of performance of test sections TShs. 496,000.00 Total Costs for Research Tshs. 1,746,511.80 APPENDIX 1: DETAILS OF FINANCIAL REQUIREMENTS Phase 1: 1.0 Field and laboratory tests Amount (Tshs) 1.1 Initial visits to Tanga, Kilimanjaro Mbeya and Kasama (Zambia) to prepare for field tests Honoraria - 0.5 man-month researcher (Kyulule) 0.5 x 88,000/= 44,000.00 Per diem 15 days x 4.800/= 72,000.00 The costs for visit to Kasama (Zambia) Will be paid separately using external funds. 1.2 Manufacture of human-towed 1.2 tonnes smooth wheel steel roller 372,738.00 1.3 Execution of field compaction trial tests (i) At Kisii and South Nyanza (Kenya), researcher (Kyulule) Costs for the researcher to be covered using external funds. Anticipated duration 2 weeks. (ii) At Tanga, Kilimanjaro and mbeya (1 month) Honoraria 1.0 man-month, researcher (Kyulule) 1.0 x 88,000/= 88,000,00 Man-month, technician (Mwaisanila) 1.0 x 44,000/= 44,000.00 Per diems 30 days x 4,800/= (Kyulule) 144,000.00 30 days x 4,800/= (Mwaisanila) (iii) At Kasam (Zambia), researcher (Kyulule) Costs for the researcher to be covered using external funds. Anticipated duration 1 week. 1.4 Soil sample testing at the Soil Mechanics Laboratory, University of Dar es Salaam Classification tests (30 samples, i.e. 5 samples from each test area) Honoraria (Technician, Mwaisanila) 21 man-days x 2000/= 42,000.00 Machine charges 30 tests x 1,200/= 36,000.00 Standard compaction tests (30 samples, i.e. 5 samples from each test area.) Honoraria (Technicians Kisimbo, Mwasanila) 21 man-days x 3,000/= + 21 man-days x 2,000/= 105,000.00 Phase 2
2.0 Monitoring of performance of test sections (i) At Kisii and South Nyanza (Kenya) Costs to be covered using external funds. Anticipated duration, 2 weeks. (ii) At Tanga, Kilimanjaro and Mbeya (1 month) Honoraria 1.0 man-month researcher (Kyulule) 1.0 x 88,000/= 88,000.00 Per diem 30 days x 4,800/= 144,000.00 (iii) At kasam (Zambia) Costs to be covered using external funds. Anticipated duration, 1 week.
2.1 Data analysis and report writing, researcher (Kyulule) 3 man-months x 88,000/= 264,000.00 SUBTOTAL TShs.1,587,738.00 BICO Charges 10% TShs. 158,773.80 TOTAL COSTS FOR RESEARCH: TShs. 1,746,511.80
DISCUSSION
Rollers The disappointing durability of the light pedestrian roller was a surprise to may participants. That piston rings on pedestrian rollers used in Lesotho needed replacement already after 3 months is serious. However, it was pointed out that some problems were caused by careless operation and a lack of or incorrect maintenance of the equipment. Problems decreased considerably after operators had been trained in preventive and routine maintenance and correct operation of the equipment. In Mozambique the experience with vibrating rollers has also been poor. Currently, the project uses tractor towed vibrating rollers. These also have not been very reliable. Towed rollers are difficult to use on narrow mountain roads where there is limited space for turning. However, this problem can be reduced by using longer pitches. In Madagascar the roads authority applies the same compaction specifications to labour-based and equipment-based works. Contractors there use heavy static towed and self-propelled rollers, because they are given on loan by the Ministry on the condition that the contractors repair and maintain them. Natural Compaction Traffic compaction and natural consolidation have been proven effective on several projects. In the rural Access Road Programme in Kenya deformation due to absence of compaction was compensated by reshaping works in the initial period after the road section was completed. Also some experimentation with light compaction by manual/donkey/oxen towed rollers was done. Although there are no data collected on this issue, not compacting and reshaping the deformed road as an (extra) maintenance activity appears to be bogh cheap and effective. The increase in vehicle operating costs has not been measured, but the roads concerned only receive a traffic of less that 30 VPD, so this cost increase is not significant. The effectiveness of natural compaction for these type of roads has been confirmed by the Transport and Roads Research Laboratory (Study unpublished). For gravel and earth roads the limited deformation is simple and cheap to rectify. However, in the case of bitumen surfaced roads insufficient compaction will lead to the destruction of the surface layers, which implies that high compaction standards are required. Separate guidelines are needed on how and when to apply natural consolidation and traffic compaction for earth and gravel works. The effect of using light weight rollers to reduce the rutting in the initial phase should be further investigated. Dry Compaction The Kenyan experience with natural consolidation and traffic compaction has been obtained in areas with sufficient rainfall. However, soil and climatic conditions differ considerably on the various labour-based programmes. In Mozambique for example water has to be broughtin by bowser or compaction has to be restricted to the 2 months per year with rainfall. Data on dry compaction would be useful for arid areas with poor access to water. The TRRL are currently doing research on dry compaction with heavy vibrating rollers in arid area in Kenya. In Namibia several studies on this topic have been undertaken using different methods, materials and maintenance systems. However, it was found that the use of water still gives the best results. Therefore, temporary pipelines have been laid from boreholes along the road alignment to the construction sites. Guidelines There is a great demand from countries establishing labour-based road programmes for guidelines on appropriate compaction methods and standards. In the past, the choice of compaction methods has been more determined by factors such as funding, available equipment, mechanical maintenance facilities or previous practice than by scientific data. As described in the papers presented, several viable and appropriate methods of compaction have been developed for labour-based road construction works. These methods will have to be incorporated in a database and accepted as viable and credible engineering. Special attention should be given to this issue when introducing contractors to labour-based works. It is then important that compaction specifications are adapted to the use of labour-based methods and that appropriate compaction methods are introduced and standardised. During the meeting an ad hoc committee of interested participants was set up to formulate their requirements. They were also requested to comment on Dr Kyulule's compaction study proposal to ASIST by mid April 1992. |
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