Pavement assessment of Thuchi-Nkubu Road B6 road
Abstract.
The pavement assessment was carried out through visual inspection and deflections. To determine the strength of the existing pavement a deflection survey was done using the rebound method. From the deflection survey, it was observed that Thuchi-Nkubu Road had a wide range of equivalent moduli. The average DBM overlay thickness required was found to be 110mm. Therefore, the contracted DBM thickness of 80mm was inadequate. The worn out sections should be reconstructed from the existing base to form the sub base. The DBM overlay of 110mm on average is required for the entire road section, however the 80mm provided for should suffice for the traffic using the road. For accesses to Chogoria, Kibugua and Igoji that are low volume, resealing was recommended. To curb further deterioration of the pavement, the road was to be maintained ahead of works.
Cracks Investigation of a Box culvert at Km 4+750 along Ilasit-Olkiloriti/Njukini Road
Abstract.
The box culvert cracks investigation involved four main tests i.e. Visual Inspection, Electromagnetic testing, Ultrasonic testing and Rebound hammer tests. From the results of the tests carried out, it was recommended that elaborate protection works be put in place to curb erosion of the back fill. Construction of another box culvert to compensate for the swell of the river should be considered.
Maintenance Study of Unsealed Roads – Dust Emission from Unpaved Roads in Kenya
Abstract.
“This report describes the problems of dust emitted from unpaved roads in developing countries through the action of traffic. The significance of the loss of material is discussed in terms of the increased regravelling requirement and the attention is drawn to the effect that dust has on traffic accidents by reducing visibility. It describes a study in Kenya which measured the rate of loss of airborne fine materials dispersed from the road relative to the speeds and types of vehicle. Recent experimental studies in the United States of America and Canada are reviewed together with a summary of their results. Methods are also reviewed of utilizing bitumens, chemicals, waste chemicals and local materials for dust proofing unpaved roads, and a critical appraisal is made of the techniques. The conclusions of the research are that most of the dust proofing treatments currently available vary considerably in their effectiveness and with the exception of the local materials, are usually more expensive than bituminous surface dressing. Where the latter techniques are unavailable, chemical stabilisers can provide an alternative solution”.
The Kenya Maintenance Study of Unpaved Roads – Research on Deterioration
Abstract.
“This report describes a study of the deterioration of unpaved roads which was undertaken in Kenya. The work formed part of a larger study of the effectiveness of various maintenance strategies on the performance of unpaved roads. The primary objective described in this report was to provide new and improved deterioration relationships for unpaved roads for use in a computer model for estimating the construction cost, maintenance costs and vehicle operating costs of roads in developing countries. Experimental test sections were located on the public road network in Kenya and their rates of deterioration were measured and quantified in terms of gravel loss of the wearing course, surface roughness, depth of loose surface material and rut depths. The test sections were monitored for a period of over 2years. The deterioration of the test sections were related to cumulative traffic, original design standards and construction, maintenance strategy and climate”.
The Kenya Maintenance Study of Unpaved Roads – Optimum Maintenance Strategies
Abstract.
“This report describes a study of the effect of various maintenance strategies utilizing both mechanical plant and labour intensive methods, on the performance of unpaved roads in Kenya. The results show that on properly constructed roads, towed graders can carry out the surface maintenance as effectively as motor graders. Towed graders can be produced in most if not all developing countries and if augmented by labour intensive methods would reduce the reliance of these countries on imported machinery for the maintenance of unpaved roads. The use of various mechanical drags for maintaining low volume roads was quantified and recommendations made for suitable designs of drag for differing road conditions. Results of labour intensive trials showed that they could be effective but that this form of maintenance is strongly influenced by the degree of supervision”.
Soil Additives - Road packer and Soil-Consolidation RPS; investigation of Effects on Soil for Road-building purposes
Abstract.
Arrangements were made between the Road packer agents and the City Council of Nairobi for the latter to prepare trial sections. The total experimental length was 600m. This was divided into 3 equal sections. Each section was then given different treatment to enable comparisons to be made between the effect of the additive and the associated processing and same treatment without an additive and the untreated section. Tests were carried during the whole study. University College agreed to carry out their own testing on Road packer. Neither of the two additives appeared to have caused any significant improvement in the soil properties tested. There were differences in the individual CBR test results but, when the averages were taken, results with and without additive were found to be similar. It was recommended that these additives were not for use in road construction in Kenya.
Investigation of Failures and Report on Pavement Strengthening
Abstract.
Investigations carried out included General observations and photographs, In-situ tests and Laboratory tests. General observation involved traversing the road while assessing the general nature of the road. A programme of in-situ testing was carried out to determine the in-situ condition and strength of the various portions of the road structure. Areas of failure and sound areas were tested for comparison. It was proposed that a 21/2” thick penetration or grouted macadam was to be laid over the full length of the road. The existing 5” base was to be re-stabilised for a length of approximately 10miles.
Penetrometric Investigation of High Embankments
Abstract.
The investigations were done using a dynamic cone penetrometer. Investigations carried out included execution of eight penetrometric tests from the top of the first fill. Two profiles of three tests were done on the second embankment, which was also located in line with the edges of the pavement. In conclusion, special attention should be given to the two embankments as well as the other fills, up to km 21, which also seemed to present problems of insufficient shearing resistance.
Strengthening of Flexible Roads in the Tropics; the use of Deflection Measurements
Abstract.
“The use of deflection techniques for pavement evaluation and the design of road strengthening measures are discussed. The concept of deflection criterion curves is introduced and their role in the road strengthening design process is described. A deflection survey procedure using hand deflection beams is outlined and a method of analyzing deflection survey data in a convenient form for overlay design is suggested”.
Derivation of Specification on Road Marking Paints and Proposed Field Trials in Kenya.
Abstract.
Road marking paints were assessed on each brands performance in a wear test, under actual traffic conditions. When the paint was applied, notes were made of its brushability and whether there was any each the bleeding of the bitumen into the paint. The time taken for the paint to reach the touch dry conditions was noted and was considered satisfactory if it was less than 15minutes. The stripes were then inspected regularly, once a month for signs of wear. An estimate was then made of the percentage of road surface showing along the line. In an attempt to quantify the wear performance of the paints, traffic flow counts for the trial roads were recorded. The results from these tests and trials outlined should greatly aid the selection of, a road marking technique and road marking materials that are most appropriate to Kenya conditions.
Experimental Stabilized-Soil Road, Makuyu, after one year in service
Abstract.
It is to be noted that during construction, cement, lime, bitumen and a chemical known as analine furfural dye were used as stabilizers. The materials stabilized were two main types of red coffee soil and a murram gravel. The road’s performance was then monitored for a period of one year. Visual inspection, In-situ CBR measurements and moisture contents for the base, sub base and subgrade were recorded. The cement stabilized mixes at 1 year was at least 140% of that at 7days cure. In situ measurements of subgrade CBR’s to date indicate that the strengths are higher than the initial estimates. For these soils with adequate compaction and favourable drainage conditions the subgrade CBR’s are usually not less than 10%. With very good drainage conditions the CBR’s obtained are substantially higher than this.
Techniques to Estimate Pavement Bearing Capacity in Kenya – Study and Assessment of Benkleman beam, Dynaflect and Dynamic Cone Penetrometer testing equipment.
Abstract.
The basis of the research was to employ different evaluation techniques on sample lengths of a number of roads representing a range of pavement types and strengths. An economic comparison for routine maintenance (between the Benkelman beam and the Dynaflect) should be based on an ‘optimal’ use of the Benkleman beam in terms of spacing number of lanes/wheel paths measured, radii and repetition of measurements.
Stabilization of soils with Reynolds Road Packer (RRP).
Abstract.
The execution of the experimental section was carried out under direction of a representative from the manufacturer/supplier of RRP. On completion of every operation, and when found necessary the Materials Branch carried out the relevant tests. From the tests of both laboratory and field, it was not possible to establish the use of RRP for road construction.
Collapsible soils in Kenya
Abstract.
The reason for investigations were to carry out further studies on collapsible soils and to present the collapse data from the 15 different sites sampled. Undisturbed samples from different sites in Kenya were tested for collapse by using oedometer tests. The loading used at submersion was the load of the actual structure on the site. Sampling techniques effects on collapse was also determined for the different sites in Kenya. The tests were then analysed and conclusions made.
An evaluation of binder ageing in Kenya
Abstract.
Due to problems Kenya experiences with binder ageing, it was decided to make a special study of this subject.The methodology for this study involved, a review of the background for the ageing problems in Kenya, a survey and digest of literature on ageing from different parts of the world, bitumen specifications, analysis of results from the laboratory for the recovered binders and evaluation of the results, thereby indicating the possible ways to reduce the binder ageing problems in Kenya.
Determination of Liquid Limit (LL) using Cone-Penetrometer and Casagrande method for some Kenyan Soils
Abstract.
This study compares test data in regard to Liquid Limit (LL) using the Cone Penetrometer and Casagrande Method.
Standard Penetration Test, SPT (N) Versus Shear Strength (Su) for Cohesive Soil (Clay)
Abstract.
This study compares test data in regard to SPT (N) values and shear strength (Su) collected from the road slide at Mikindani, Mombasa
The Effect of tyre pressure on the Road Deterioration in Kenya with emphasis on Low traffic Roads with Thin Bituminous Surfacings.
Abstract.
This study investigates the effects of tyre pressures on the road deterioration in Kenya with emphasis on Low Traffic Roads with thin Bituminous surfacings. A literature study was first done on the road deterioration caused by tyre pressure. A tyre pressure survey was then done. The axle load and tyre pressure were measured on a total of 654 heavy trucks at five different locations namely, Athi River, Gilgil, Ruiru, Mariakani and Kiambaa. In situ testing of the gravel base materials was then carried out using a portable Dynamic Cone Penetrometer. A PC based computer program, CHEVRON was then used to investigate how tyre pressure deteriorates the five different road sections in Kenya. The computations were based on results from the axle load and tyre pressure survey, pavement construction data and traffic data from the actual sites.
Roughness Measurements of the Paved Road Network
Abstract.
Roughness measurements were taken continuously and the value for each half kilometer section was recorded by presetting the counters. The towed bump integrator was used to carry out surveys; the instrument was towed at a testing speed of 32km/hr and frequent checks were made to correct the tyre pressure and fluid levels in the dashpots. Visual inspection was also done in a support vehicle of the construction and the condition of the road pavement and any maintenance measures that had been carried out in the previous survey. The data obtained was then analysed.
Early Performance of Some experimental Bituminous Overlays in Kenya
Abstract.
“This report describes the performance of bituminous overlays on roads in tropical and sub-tropical environments in Kenya. Considerable hardening of the binder occurred throughout the depth of the overlays during the first five to seven years, but negligible rutting developed. The main form of deterioration was, cracking which was initiated at the surface of the overlays. The reduction in pavement deflections produced by the overlays is shown to be only slightly less than those obtained in Britain despite the higher ambient temperatures in Kenya. The performance of the overlays is shown to be primarily dependent on the properties of the overlay material itself. No correlation could be established between the development of cracking on each test section and the corresponding values of surface deflection and curvature, traffic loading or overlay thickness. However the overlays have remained serviceable for up to seven years and have carried up to 43 x 106 equivalent standard (80kN) axles”.
Alternative Soils Stabilizers-Anyway (RBI)
Abstract.
The tasks under this research included Laboratory trials which was done in 2005, Construction of the trial section on the 120m section of Machakos-Kangundo Road with RBI stabilised gravel base and subbase was carried out under contract between the months of March and November 2008. The research is currently under a baseline evaluation which is to be finalised this financial year
Alternative Soils Stabilizers-Permazyme
Abstract.
The tasks under this research included Laboratory trials which was done in 2005, Construction of the trial section on the 400m section of Machakos-Kangundo Road with Permazyme stabilised gravel base and subbase was carried out under contract between the months of March and November 2008. The research is currently under a baseline evaluation which is to be finalized this financial year.
Alternative Soils Stabilizers-Superpave
Abstract.
Due to problems Kenya experiences with marginal soils such as black cotton and red coffee soils, it was decided to carry out trial sections with addition of soil stabilizers with an aim of improving their properties. Demonstration trials were carried out on the Northern bypass near Ruiru in 2005, Construction of the trial section with superpave was carried out. Laboratory trials are ongoing in preparation for road trials proposed for Kenol-Koma Road on a 3km section.
Alternative Soils Stabilizers-Novocrete
Abstract.
A delegation from the Ministry of Roads visited the manufacturer plant for Novocrete (Infracrete) in Germany in 2008. Laboratory trials will be carried out this financial year (2014/15)
Alternative Soils Stabilizers-Probase
Abstract.
Due to problems Kenya experiences with marginal soils such as black cotton and red coffee soils, it was decided to carry out trial sections with addition of soil stabilizers with an aim of improving their properties. Laboratory trials for probase have commenced. Field trials to be carried out on Kabete-Kikuyu road, on a 7km unpaved section under funding by Kikuyu Constituency Development Fund.
Alternative Soils Stabilizers-Pavezyme
Abstract.
The additives for Pavezyme were proposed in the year 2014. A review of the manufacture's specifications, environmental compliance certification from country of origin (USA) and verification protocal has commenced.
Dowel Jointed Plain Concrete Pavement
Abstract.
A trial section on Dowel Jointed Plain Concrete Pavement was constructed on Mbagathi Road Nairobi with the assistance of cement manufacturers association. A post construction performance evaluationto inform development of design procedures and construction specification is yet to be done to finalize on this study.
Road Research Unit Organization
Abstract.
Ten areas of study that have the highest priority for the MOW are presented. The extent of each research is clearly defined. A programme for execution of the work is then presented which defines: the forecast procedures required to accomplish the various studies, the planning of the engineers and field teams activities and the personnel and equipment required for satisfactory completion of works in the allowed timescale.in addition the appendices attached to the report define in more detail, the line of study, the objection of each step of the work and the timetable. It was concluded that the research operations would be done in three stages: preliminary investigations, study and analysis and reporting. All the studies directly connected with road construction would be concluded by reports giving recommendations for changes in the MOW Specifications. These reports would be of two types: (1) Reports which will close the research by giving conclusive advice. (2) Provisional documents which will need confirmation from further research.
Bitumen Standard Pavement Design
Abstract.
Sources of hardstone for this project were Mazeras-Kokotoni area, Ribe and near Kaloleni, 3Km along the road to Mariakani.
A standard procedure for a Pavement Condition Survey and a Preliminary Overlay Design method
Abstract.
In order to predict the appropriate measures, a frequent assessment of the pavement condition and its residual strength is required. Preferably this has to be carried out by a simple, little time consuming, non-destructive method. The report is meant to describe a standard procedure to assess a pavement condition and residual strength.
Gravel Standard Pavement Design
Abstract.
Sources of hardstone for this project was Manga ridge
Bitumen Standard Pavement Design
Abstract.
It was known from previous materials investigations for previous construction, which the sandy soil excavated as side cut approximately 3 to 4km from Machakos gave excellent results when stabilized with cement, and that the present base course is composed of this. No surfacing stone was eminently suitable for purpose of Surface Dressing. The project would purchase the surfacing stones from Kamavir Quarry, Sultan Hamud.
Bitumen Standard Pavement Design
Abstract.
Hard rock source was found to be from suppliers in the vicinity of Thika Township. Hard rock suitable for crusher run, water bound or hand packed stone construction was found to be available from the Anglo French quarry in Thika Township. No difficulties were expected concerning water supply as the road runs closely to the Kyama River which has a permanent flow.
Gravel Standard Pavement Design
Abstract.
Quarry 1A, or the Van Niekerk, Kleyn and Edwards' or Vihiga quarry which is located near Bukuga Market and an Existing quarry No.* located 7.8kms from Kima (or Ekhomo) Market on the road to Ebusiololi School were the only two used as source of the wearing course gravel.
Bitumen Standard Pavement Design
Abstract.
Potential quarry source was the Angle-French Quarry in Thika Township
Investigation of Pavement Construction
Abstract.
A one mile long section was investigated. This section started at Racecourse Road near Kariakor Market, passing through Juja Road and finishes at the Junction with Kirtar road. Visual inspection of the road was done and photographs taken to give a general picture of the area. Three trial holes were dug at specific places to assess the pavement conditions.The line and level of kerb were usedas datum in measuring the profile of the road. Surfacing investigation was done by separating the aggregates from the bitumen to give a rough guide to the sizes of stone chippings used. A visual assessment of the basecourse was done and samples of the stone used were taken to the laboratory for testing. Insitu CBR and dry density tests were carried out on the subbase layer. Only insitu CBR test was carried out on the subgrade. In conclusion, as a matter of urgency, it was required to seal the surface to stop the ingress of water. It was advised that it was only necessary to make up the surfacing to acceptable levels and falls for the road to be fully serviceable since the pavement itself was found to be sound.
Investigation of Failure and Pavement Design for proposed new construction
Abstract.
A total of eleven holes were dug at five locations within the length of the road. Three of these locations were coincident with the ones that had been inspected in July, 1963, but the holes were dug to the left and right of the centreline, whereas the previous ones were dug at the centreline. The construction profile was exposed at each hole; these were recorded and samples of base/subbase and subgrade were obtained for laboratory testing. The results were then analyzed and conclusions made.
Experimental Sections at Mau Summit
Abstract.
The experimental sections including the single width construction were put down in 1957. In order to obtain a picture of the soil profile and conditions exploratory holes were put down at intervals on all sections including single width and standard construction. The holes were referenced as A and B. The 'A' (main) tests comprised in-situ CBR on the bitumen surface and subgrade, while tests on 'B' (exploratory) holes were for moisture only. The field work was carried out during a rainy period in September 1962. The test positions were all located in the outer wheel track at approximately 3ft from the road edge.
Bitumen Standard Pavement Design
Abstract.
It was known from previous materials investigations for previous construction that the sandy soil excavated as side cut approximately 3 to 4km from Machakos gave excellent results when stabilized with cement, and that the present base course is composed of this. No surfacing stone was eminently suitable for purpose of Surface Dressing. The project would purchase the surfacing stones from Kamavir Quarry, Sultan Hamud.
Excessive Axle Loading Curtailment of Road Pavement Life
Abstract.
The purpose of the research was to know accurately the axle-loading spectrum that the pavement surface will encounter during its life, as well as the predicted total number of vehicles travelling. These figures may be derived from traffic surveys. The average damaging power of the commercial vehicles on this road was found to be 4.64 standard axles per commercial vehicle. In order to approach the expected design life of the Mombasa-Nairobi road, or any other road in any other country, two alternatives are available, to either enforce the legal loading limit or to redesign the existing and proposed roads to very much higher standards to carry overloaded vehicles, with a consequent sharp increase in construction cost. In conclusion, it suffices to say that overloading above the legal axle limits cause existing pavements in Kenya to fail prematurely, as would also be the case for pavements scheduled to be constructed to the existing design standards. To accommodate the present uncontrolled overloading attributed to a minority of road users, the economy of the country would need to bear the high cost of reconstructing the existing and proposed to very much higher design standards. To avoid such an expensive programme, it was necessary to enforce the legal maximum axle weight legislation.
Paint Testing: Comparison of Artificial and Natural Weathering
Abstract.
In 1967, a consideration was given to the speeding up of the exposure-testing programme by the purchasing of an artificial weathering device. However, prior to this decision, it was found necessary that a correlation test would be carried out to establish whether, the particular conditions found in Kenya could be simulated in a reasonable length of time by such a machine, and whether, purchase of this equipment represented a viable proposition in terms of cost and personnel. It was concluded that no useful purpose would be served by using the artificial weathering device in the paint testing programme, and that the basis of test and assessment should remain natural weathering.
Road Surfacing Premix
Abstract.
The investigations carried out at Kingston Road Depot were on the materials supplied eg the stone grading and their properties, mixing procedures and temperatures, the analysis and properties of the mix, and the procedure used during laying. Samples of the premix production during the month of June 1968 were obtained from Kingston Road Depot and were tested for the Standard Marshall Stability Tests, they were also analyzed to determine the bitumen content and stone grading. An analysis was also done for the previously laid surfacing (sound and unsound). A visual examination of the sample taken from the sound area, Liverpool Road was done. Samples from unsound areas were taken from Fort Hall - Victoria Street - Grogon Road roundabout and Sclaters - Kikuyu Road roundabout. Compliance with relevant BSS was also to be confirmed. It was recommended that mixes and procedures based on BS 1621 'Bitumen Macadam' should be adopted.
Soil stabilization for Roads: Consideration on Specifications of Stabilizer Quantities
Abstract.
In carrying out the reassessment of the maximum and minimum stabilizer quantities to be used, a critical re-appraisal was made based on practical construction experience, and on theoretical considerations developed from existing data concerning mixing efficiency. The conclusions derived were then compared with the limiting quantities apparently used in other countries.
Investigation of Failures and Report on Pavement Strengthening
Abstract.
The road was traversed various times and a number of observations and assessments of a general nature were made. Photographs were taken to record information and illustrate certain points. In-situ testing was then carried out to establish the in-situ condition and strength at various portions of the road structure. Tests were done on all the various types of construction materials, for comparison of the various sections. Areas of failure and also apparently sound areas were tested, for comparison. Test positions of the failed areas were located at points where the surfacing was still intact, but in the vicinity of points where disruption was taking place. The samples from the in-situ test positions were then tested in the laboratory. Typical samples obtained from quarry sites were tested in a similar manner. These were meant to provide information on the material available for use in construction. The results were then analysed and conclusions made.
Port Reitz Airport, Mombasa - Earth slips
Abstract.
Visual inspection was done. Three holes were drilled mechanically behind the slip and one auger hole wash and drilled near the bottom of the slip on the western edge. Tests were then carried out and results analyzed before conclusions were made. It was recommended that further erosion would be prevented. Installation of some form of the interceptor drain, to prevent the ground water reaching the face. Another alternative would be to move the runway threshold in considerably accepting that there will be a gradual erosion of the existing cliff edge
Overloading on Nakuru-Malaba Road
Abstract.
Traffic analysis at Timboroa on 5/5/1975 was first compared with the traffic analysis at Timboroa on 6/3/1976. The equivalence factors for Buses, Medium Goods Vehicles, Heavy Goods Vehicles and Oil tankers were compared and analyzed. Traffic analysis for Origin -Destination at Timboroa and Mtulo (3km west of Webuye) were also analyzed. The information was then presented graphically. From the foregoing analysis done, conclusions and recommendations were then made.
Assessment of the Nairobi - Mombasa Road
Abstract.
The assessment was based on three sets of Benkleman Beam deflection results obtained in 1973, 1974 and 1975 and on the results of systematical observation of the defects which have been carried out from km 100 to km 374. A comprehensive analysis of the deflection results was carried out, the main aim of which was to define a deflection criterion for the assessment of different pavement structures, and to point out the guidelines of a strengthening procedure.
Assessment of Low Standard Roads - Assessment of Lanet-Dundori Road
Abstract.
The assessment was based on February 1977's Benkleman Beam deflection results and on the results of a systematical observation of the road defects as stipulated in the New survey techniques set up by the Road Research Unit. The investigations carried out involved collection of as many data as possible to enable completion of the assessment. Traffic data, Pavement structure data and the pavement condition data were evaluated. Traffic data was evaluated by referring to results of traffic counts which had been made since 1957. Using the relevant equivalence factors the number of cumulative standard axles were also presented. The nature and thickness of the different pavement layers was determined by digging of trial holes on the verge-side edge of the carriageway and at intervals of one kilometer. Deflections measured with a Benkleman Beam were the first criterium which were taken to assess the pavement. The pavement defects were recorded at each testing point on 200m long stretch.
Assessment of Low Standard Roads - Assessment of Naivasha-Kinangop Road (C67-D393)
Abstract.
The assessment was based on February 1977's Benkleman Beam deflection results and on the results of a systematical observation of the road defects as stipulated in the New survey techniques set up by the Road Research Unit. The investigations carried out involved collection of as many data as possible to enable completion of the assessment. Traffic data, Pavement structure data and the pavement condition data were evaluated. The traffic counts were carried out at a point East of Naivasha on C67 and on its junction with D393.
Assessment of Low Standard Roads - Assessment of Nakuru-Solai Road
Abstract.
The assessment was based on February 1977's Benkleman Beam deflection results and on the results of a systematical observation of the road defects as stipulated in the New survey techniques set up by the Road Research Unit. The investigations carried out involved collection of as many data as possible to enable completion of the assessment. Pavement structure data, Traffic data and the pavement condition data were evaluated. A measure of the material strength and thickness of each layer was needed to provide an idea of strength for the complete pavement. In-situ CBR measurements plus subsequent laboratory testing of the samples obtained from the testing points were used as the basic measure of strength of the various pavement layers. Pavement condition data was composed of measured surface deflections using Benkelman Beam for evaluation of structural condition and recorded pavement defects to indicate the type and degree of extent of the pavement deterioration. The cumulative traffic was
Road Marking Paint Failures on Mombasa Airport
Abstract.
A 3 months research was carried out in Nairobi, in Materials branch laboratories along Gilgil-Olkalou road and in Nakuru as follows: a) Stripes of the failed brand was applied together with other brands on the same runway sections; these were then assessed to ascertain whether the same patter nof failures occurred. b) Sections of the failing stripes were scraped off by the contractors and fresh markings applied. c) Typical runway surface cores were prepared in the Bitumen Laboratory and marked immediately with the failing brand and another brand of good quality. d) Markings of the falling paint sample were made on an old road surface near the railways workshop and monitored for identical failures to those observed on the runway. e). The same test as in d) above were carried out in Nakuru along Gilgil-Olkalou Road.
Investigation of an embankment failure - Njoro-Mau Summit road (C56) (Elburgon fill)
Abstract.
Since seepage had taken place at various levels of the embankment slopes, it was evident that water was present within the fill and the purpose of the investigation was to locate the water flow paths and the corresponding sources. Five pits were dug through the pavement to a depth of 1.5m; three of them were dug in the area with deformation and cracking and the other two were dug at the end of the embankment assumed to be in good condition. Four trenches were also dug by hand, upstream and perpendicular to the left ditch; these were meant to point out the functionality of the drain. An observation was then done, and the results analyzed before the conclusions were made.
Two Computer Programmes for Road Maintenance and Research
Abstract.
These two programmes were written with considerable assistance of the staff from Central Bureau of Statistics under the control of Mr. R. Torkington. For the weighbridge, the programme took the recorded weight of each axle of the commercial vehicles weighed, turned this into equivalent number of standard axles, summed this figure for all vehicle types and produced the overall number of standard axles that each vehicle would exerton the pavement (Equivalence Factor). For deflection, In order to simplify interpretation of the deflection data, a subroutine was written to plot the definitive deflection against distance. The programme would then automatically calculate the optimum scale to use for deflection and would use one line throw per km distance.
Assessment of Low Standard Roads - Assessment of Nakuru-Solai Road
Abstract.
The bitumenised section of the Nakuru-Nyahururu road (B5) forms the part of the Nakuru-Solai section which is the subject of this study. The assessment was based on February 1977's Benkleman Beam deflection results and on the results of a systematical observation of the road defects as stipulated in the New survey techniques set up by the Road Research Unit. The investigations carried out involved collection of as many data as possible to enable completion of the assessment. Traffic data, Pavement structure data and the pavement condition data were evaluated. To obtain the cumulative traffic since year of completion of construction, interpolation for the years lacking any traffic had to be done. From these cumulative traffic, the number of cumulative standard axles which have used the pavement were obtained. Using the relevant equivalence factors the number of cumulative standard axles were also presented. The nature and thickness of the different pavement layers was determined by digging of trial holes on the verge-side edge of the carriageway and at intervals of one kilometer. Deflections measured with a Benkleman Beamwere the first criterium which were taken to assess the pavement. The pavement defects were recorded at each testing point on 200m long intervals.
Evaluation of Vehicle Weight Statistics
Abstract.
Traffic data from the Trans Africa Highway was reviewed during this study. A computer programme was used by the Roads research Unit which calculated the equivalence factors from the existing traffic, applying legal limits and then showed traffic increase caused by absolute legalization. This increased traffic was then tabulated by calculating the number of vehicles required to carry excess goods removed from axles which exceed Legal Limits. The excess axle loads were only considered as increased Equivalence factors. The increase in traffic to carry the same Load caused by absolute Legal Limit enforcement was also presented for the various types as a percentage of the Total number of that vehicle type.
Nyeri Area Stone Survey
Abstract.
Investigations for a potential hardstone site was carried out in two stages. The first stage consisted of proving the soil overburden and taking preliminary stone samples for laboratory testing. The second stage consisted of diamond drilling and supplementary stone sampling. The soft stone site investigation of the tuff quarries was limited to taking representative stone samples for laboratory testing. The reason why nothing more was done was that stone quarries were being worked.
Mombasa-Nairobi Road Stone Survey
Abstract.
Investigations for a potential hardstone site was carried out in three sections: From Mombasa to Mackinon Road, From Mackinnon Road to Emali and from Emali to Nairobi.
North Coast Stone Survey
Abstract.
The area covered during the study included part of the Coast between Mombasa and Malindi and extended about 50km inland. A key plan of the sites investigated was given together with the geological boundaries. For identification, each Materials site was given a reference number. The research considered each geological rock type in turn, listing worked sources or outcrops investigated and engineering properties. The location of the sites was defined by reference to the UTM grid system to an accuracy of +/- 50metres. To obtain this, the map series Y731 Scale 1:50,000.
Kisumu Area Stone Survey
Abstract.
A key plan of the sites investigated was given together with the geological boundaries. For identification, each Materials site was given a reference number. The research considered each geological rock type in turn, listing worked sources or outcrops investigated and engineering properties. The location of the sites was defined by reference to the UTM grid system to an accuracy of +/- 50metres. To obtain this, the map series Y731 Scale 1:50,000.
Makutano-Muranga Road - Report on Karugia section Failure
Abstract.
Karugia section had failed at two positions approximately 250m apart. The section being assessed was across the Kariara river valley in a large water catchment area. A visual inspection was done; this was accompanied by taking of photographs to show the manifestation of the failures. A rough sketch of the failed sections was then made. Recommendations were then made from the observations and tests carried out.
Report on a visit to Kwale District, Kenya for a survey of Gravel Resources for the rural access roads construction programme
Abstract.
The visit was made over a period of 7days in September 1978.During the survey, it became necessary to clarify the terminology with reference to engineering gravels. In this study, the term "gravel" applied to any reasonable hard material of a size between 2 and 60mm. The team also used the aerial photographs from Survey of Kenya during the study. The gravels reviewed during the visit were referred to as laterites or murram. The region was noted as being divided into four distinct topographical and geological zones, ie the coastal plain and coral reef, the central low hills region and laterites of Mrima and Kiruku Hills, Shimba Hills and the Kwale laterites and the Inland Plains and the fractured sandstones.
Tana Basin Road Project Phase II - Hola-Garsen-Malindi (B8) Road, Results of Full-Scale for Lime-Improved subgrade.
Abstract.
The study involved field trials results of lime treatment of silty clays of SI quality and analysis of their possible use as subgrade. The tests conducted include Grading, Atterberg limits, MDD/OMC relationships, CBR's ($days soak on untreated materials), CBRs (7days cure+7days soak on treated material), Insitu densities and In-situ CBRs by DCP. The results are analyzed and recommendations are then made.
Experimental Bitumen-Mackinnon Road
Abstract.
Construction started on 5th February 1963. The total length of construction was 3.9mile ie. 206 chains (6km)of which 95 chains comprised gravel section and 111chains earth section. These 111 chains were further treated as 106chains bitumenised and 5 last chains cement-stabilized. From the soil survey results, it was decided to carry out the experiment on the soil as a base course under prime and single seal and prime and double seal. Drainage comprised 2ft diameter culverts at Chainage 153, 193 and199. 4mitre drains had so far been dug and improvement on drainage had been promised as soon as the weather permitted.
Thuchi-Nkubu Road Evaluation Study: A Baseline Study of Rural Transport Services
Abstract.
The baseline study involved interviewing as many people as possible of the regular bus and matatu drivers operating on the northern half of the present Thuchi-Nkubu road (B6) on feeder roads leading from B6, north of Igoji into surrounding agricultural areas, and on any direct route between Meru and either Nairobi or Embu. Interviews were conducted primarily at Meru and Nkubu which were the two major starting points for both long distance passenger traffic travelling to Embu and Nairobi, as well as being the major destination for short distance rural passenger traffic. Information was collected on the characteristic of the vehicle (basic), routes driven the previous week, the number of daily trips and distance covered, Time start and finish, transportation charged on each section in the wet and dry season and driver's wages and views on the route alternatives available in response to the upgrading and realignment of the Thuchi-Nkubu road. The results were then analyzed and conclusions were then made.
Thuchi-Nkubu Road Evaluation Study: Rural Passenger Travel Demand, Surveys
Abstract.
The survey was aimed at collecting personal travel information from all members of selected households in cluster sample village areas. The surveyed villages were located at varying distances from the alignment of the B6 and from Meru and Nkubu. 12 villages were chosen, four of which were adjacent to the B6 road. Two other sites located east of the road and four on the west were selected based on the degree to which the road improvements were expected to affect their travel patterns and by distance from Meru Town. A further two sites located on either side of the road were located between Nkubu and Meru; they were not expected to be affected by the improvement of the road B6. They were chosen as controls on the rate of change in the transport area. The selection of the village sites and the households was done by the Central Bureau of Statistics by random selection to give a greater statistical validity to the survey results. The survey consisted of four parts, an interview survey, a weekly travel log, travel needs questionnaire and an accessibility and road condition sheet. Five questionnaires were used during the survey, four were given to each and one applied to each survey area as a whole.
Thuchi-Nkubu Road Evaluation Study: Baseline and First Year Traffic Data
Abstract.
The survey was aimed at collecting personal travel information from all members of selected households in cluster sample village areas. The surveyed villages were located at varying distances from the alignment of the B6 and from Meru and Nkubu. 12 villages were chosen, four of which were adjacent to the B6 road. Two other sites located east of the road and four on the west were selected based on the degree to which the road improvements were expected to affect their travel patterns and by distance from Meru Town. A further two sites located on either side of the road were located between Nkubu and Meru; they were not expected to be affected by the improvement of the road B6. They were chosen as controls on the rate of change in the transport area. The selection of the village sites and the households was done by the Central Bureau of Statistics by random selection to give a greater statistical validity to the survey results. The survey consisted of four parts, an interview survey, a weekly travel log, travel needs questionnaire and an accessibility and road condition sheet. Five questionnaires were used during the survey, four were given to each and one applied to each survey area as a whole.
Case History of Some Examples of Engineering Problems encountered in the Red Clay soil.
Abstract.
A research was carried out on three highway embankments made up of red clay soil on Limuru-Uplands road; where longitudinal cracking had cut across the bituminous pavement on the road surface. The study also involved laboratory laboratory testing on the red clay soils that formed the embankment and cause of cracking. A research was also carried out on Eldama Ravine-Nyaru Road which was constructed around 1986 and experienced cracking on pavement of the embankments during construction at Km 6+200, 6+300, 13+600 and 29+500. The block and long curved cracks occurred on the outer part of super elevated part of the finished roads.
Hydraulic binders (with motor strength less than 42.5N/mm2)
Abstract.
The tasks under this study will include Laboratory trials, Design and construction of road trials, post construction baseline pavement evaluation and performance monitoring and procurement of consultancy contract for this exercise.
Bitumen Stabilized Gravel
Abstract.
A trial section of Formed bitumen Stabilized gravel subbase was constructed on 11.3Km section on Karatina-Marua Road under the contract for rehabilitation of Muranga-Sagana-Karatina-Marua (C73/A3) road between 2006-2007. Baseline pavement evaluation involving traffic and pavement condition surveys was scheduled to start in the year 2014.
Foamed Bitumen Stabilized Gravel
Abstract.
A trial section of Formed bitumen Stabilized GCS base was constructed on 89.9Km section of Mai mahiu - Narok (B3) road under the contract for the rehabilitation of the road which was substantially completed in 2010/2011. Baseline pavement evaluation involving traffic and pavement condition surveys was scheduled to start prior to the expiration of the defects liability period.
Low Cost Surfacing for Semi-Arid Areas MOW/NRRL project 1977-1980 Turkana Road Trial Sections 1978 Performance.
Abstract.
The Turkana trial sections were inspected on August 26th 1978 by Mr.E. Hansen, MOW, Nairobi, Mr.T. Thurmann-Moe, NRRL, Oslo and Mr.G.Refadal, NRRL, Oslo. As a result of this inspection, a description of the performance of each section was done. Based on the performance, estimated service life, availability of materials and a cost estimate for each type of surfacing, a recommendation regarding type of surfacing was given by NRRL.
Uyole-Tukuyu Road, Tanganyika-Stabilization of Volcanic ash
Abstract.
The un-stabilized samples were received and their moisture content recorded. The samples were then tested for grading, plasticity and British Standard (Proctor) compaction, and CBR tests. Chemical tests to determine the organic matter content, sulphate content and pH. Three typical samples were tested for stabilization with 6% cement and 6% lime. CBR tests were also carried out 100% proctor at OMC. The results from the observations and tests done were then analyzed before the conclusions were made.
An Investigation into the Dry Compaction of Lateritic Sandy Gravel.
Abstract.
'This paper discusses the possibility of dry compaction of lateritic sandy gravel. Reduction of construction costs in arid and semi-arid areas of the Tropics by reducing the amount of water used for compaction, may be possible, due to the fact that certain lateritic sandy gravels have high densities when compacted dry which are comparable to those obtained at optimum moisture contents. Recent investigations carried out at the NRRL on lateritic sandy gravel from Turkana (Kenya) are discussed. Similar results obtained from Norwegian material with similar gradings are presented. Other related work published by other authors is reviewed. It is concluded that the application of dry compaction for lateritic sandy gravel may be possible if systematic laboratory tests are carried out before the material is chosen. There appears to be no obvious criteria for the use of dry compaction for any particular type of lateritic sandy gravel. Grading, fine clay particles and soluble salts may have great influence on the results obtained.”
Kenya Low Volume Roads Study - An Investigation into the use of Lateritic and other locally occurring materials as bases for bituminous-surfaced low volume roads – Report on the Completion of the Phase I Programme - Volume III
Abstract.
The site and laboratory tests were carried out by two independent teams, to provide a check on the test results; one from the University of Nairobi and the Government Materials testing laboratory. In situ density tests were carried using both the sand replacement and nuclear density methods. A troxler Density Moisture Gauge was used for the nuclear density measurement. At the time of carrying out the density tests it was decided to carry out additional tests which would be useful for interpreting the results. The additional tests included Clegg Impact Hammer Tests on the surface of the base course and on the surface of the subgrade, Dynamic Cone Penetrometer Tests on the base course and the subgrade, Grading, Liquid and Plastic Limits on the base course and Heavy Compaction Tests on the base course. The test results and observations made were then analyzed before conclusions were made.
Turbo-Webuye Road-Assessment of the condition and proposals for remedial measures
Abstract.
Various data compiled to assess the condition of the pavement included:-A longitudinal cross section obtained from trial pits dug every 2km.-In-situ and laboratory tests to assess the nature and strength of the pavement layers-Deflection values together with radius of curvature measurements. The deflection data was obtained from results of routine deflection measurement carried out in 1973/74 and further deflection measurement to elaborate on the data.-The nature and extent of defects encountered on the road, which was done through visual inspection and through observation, and testing of cores from the road structure. Proposals for remedial measures were then given after analysis of results.
Performance Evaluation of Geo-synthetic -Reinforced Earth walls
Abstract.
This was a comprehensive analysis and structural evaluation on the RE-wall structures along Thika road (A2)
Studies of GRI on Embankments and Pavements
Abstract.
Comparison between unreinforced and Reinforced sections along Webuye-Malaba road
KEN-042 Study on low volume roads
Abstract.
The trial sections were constructed, then their performance monitored for a period. This is still ongoing.
Research trials on alternative stabilizers
Abstract.
The stabilization trials were carried out on in-situ soils especially clays, silt and gravel using 2%-6% of ANSS soil stabilizers.
Research trials on labour intensive low cost bitumen surfaced pavements
Abstract.
The research was aimed at providing cost effective rehabilitation for paved roads, develop specifications for low volume seals and to provide practical training to regional districts.
DCP Design Method
Abstract.
DCP tests were done on the existing road sections during wet and dry seasons of the year
Pavement Design Guidelines for low volume sealed roads in Kenya
Abstract.
This study was aimed at providing a pavement catalogue for upgrading low volume roads to paved standards.
Study of performance of locally available quartz gravel utilized as stone material in the surfacing
Abstract.
Study the performance of locally available quartz gravel utilized as stone material in the surfacing in order to avoid the high cost of importing chippings from the nearest commercial quarry near Naivasha, a distance of 160Km.
Assessment of low standard roads
Abstract.
The assessment was based on Benkleman beam deflection results obtained in February 1977 and was aimed at presenting an analysis which would lead to optimization of pavement design of these types of roads.
Pavement Evaluation and Overlay design
Abstract.
The pavement structure was evaluated and an overlay design done
Transportation study for ore movements from Kimwasor Flourspar mine
Abstract.
Following the decision to exploit Kimwasor fluorspar mine, it was deemed necessary to examine the effects, which transport of ore between the mine and main railway line to Mombasa might have on the public highway system and investigate possible alternative modes of transport.
Un-surfaced Base Investigations
Abstract.
The research was carried out to investigate the effects of leaving a newly constructed unstabilized road base unsurfaced for a short period.
Current road policy issues in Kenya with particular reference to axle load limits, Road User charges and Road Safety
Abstract.
To review existing axle limitation in order to check its adequacy given the vastly changed traffic situation and operating circumstances.
Foundation conditions in Red soil
Abstract.
Settlement characteristics are summarized in such a way that they give useful information on the basis of very little laboratory testing.
1983 World Survey of Current Research and Development On Roads and Road Transport
Abstract.
The research was aimed at collecting information of current research and development on roads and road transport from each country; these are then presented in a three-year cycle. During the first year of a country cycle, the report carries a complete re-survey. In the following two years of a country cycle, a supplementary survey is undertaken. Projects found to have been finished are described as ‘complete’ in the yearly report once.
An Investigation to determine the structural capacity and rehabilitation utilization of a road pavement using the pavement dynamic cone penetrometer
Abstract.
The investigation focused on the application of DCP to the rehabilitation design for a thin surfaced gravel pavement which was showing signs of distress.
An Investigation into the use of Lateritic and other locally occurring materials as bases for bituminous-surfaced low volume roads.
Abstract.
The study involved investigation on four trial lengths of low volume roads in Kenya in which non-standard locally occurring laterites and quartz gravels have been used as base course. The study was aimed at determining the savings in construction costs made by using non-standard quarry with laterite and quartz gravels in place of crushed stones.
A study of Bitumen and Bituminous mixes for Road pavements in Kenya
Abstract.
Ministry of Public Works and Housing and European Commission for development requested the Transport Research Laboratory (TRL) to identify the causes of premature cracking and in particular, of plastic deformation in bituminous hot mix surfacing in Kenya and to provide a methodology for mix design which would curb such failures.
Surface dressing in Developing Countries: Research in Kenya
Abstract.
Jackson (1963) proposed a method of Surface dressing Design based on ideas put forward by Hanson (1935) which incorporates the concept of average least dimension. This method was used to design 27 Km of experimental sections during 1975-77 in Kenya. They were then monitored during the first 3-4 years of trafficking.
Investigations into the likely causes of failure of the Embankment at Mikindani on A109 road
Abstract.
The purpose of the research was to investigate the likely causes of the slide of embankment at Mikindani (Mombasa) on A109 road.
A preliminary Investigation and Assessment of the overlay strengthening requirements and defects of the paved areas at JKIA, Nairobi
Abstract.
The Materials Branch was requested to carry out a deflection survey using the Benkleman Beam equipment in conjunction with a standard crack and defects survey. The results were then analyzed, recommendations made for improvements, remedial treatment and pavement strengthening overlays to rehabilitate the airport pavements for a further 10years.
Evaluation of Vehicle weight statistics in Kenya for the period 1977-1984
Abstract.
It was important to establish a picture of the commercial vehicle population using the routes to enable the trends to be identified and therefore permit reasonable predictions to be based on the annual traffic count data. It was essential to be able to predict the loading, which the road was expected to carry during its design life. It was concluded that certain commodities should be transported by rail or pipeline and it would be in the interest of the government entities therefore that the vehicle load regulations be made effective and hauliers be responsible for their true share of costs.
Preliminary Report on strengthening of the Nairobi-Mombasa road
Abstract.
To assess the required strengthening, investigations on quality and quantity of the existing pavement layers were done. A standard test procedure using benkleman beam was adopted. An assessment of the required overlay was done by deriving design curves for use in Kenya from curves published by the Canadian Good Roads Association. Level of comfort experienced during driving, visual assessment of the condition of the pavement and the measured Benkelman Beam deflections indicate that the pavement of the whole Nairobi-Mombasa road needs improving and strengthening. Some sections have adequate width, the remainder needs widening.
An Improved Data Base for Estimating Vehicle Operating Costs in Developing Countries
Abstract.
'This report describes, an investigation undertaken by the Transport and Road Research Laboratory in co-operation with the International Bank for Reconstruction and Development (IBRD) in Washington; to compare the data base of the vehicle operating cost relationship, derived in the joint TRRL/IBRD Kenya road transport cost study with that of the World Bank Staff Occasional Paper No 2 "Quantification of Road User Savings".
Road Deterioration Parameters for Estimating Vehicle Operating Costs in Developing Countries
Abstract.
'Tables for estimating vehicle operating costs on rural roads in developing countries have been published by the Transport and Road Research Laboratory. This report gives guidance to users of these operating cost tables on values of surface roughness, rut depth, depth of loose material and surface moisture content which correspond to various road construction standards, traffic loadings and growths and for different maintenance policies. The values of road deterioration parameters given in this Report are based on field observations made by the Laboratory in Kenya."
Revision 1 of the Road Transport Investment Model
Abstract.
''Separate equations relating road roughness to traffic loading or each integral and half integral value of modified pavement structural number were incorporated in the Road Transport Investment Model. It has been found necessary to interpolate between these relationships for intermediate values of modified structural number and so they have been replaced by a single equation relating roughness, traffic loading and modified structural number in a continuous manner. Similarly the separate equations which related road surface cracking to traffic loading for each value of modified structural number have also been replaced by a single equation. In addition the data obtained in Kenya have been extrapolated to include a wider range of pavement structural numbers and higher levels of traffic loading. The speed estimating equations for medium and heavy goods vehicles on both paved and unpaved roads have been modified to include the effect of vehicle power-to-weight ratio. Finally the equations relating vehicle wastage to vehicle age have been improved to ensure that the first derivative of the wastage function is continuous in the range of interest."
The Kenya Road Transport Cost Study: Research on Vehicle Operating Costs
Abstract.
''This report describes an investigation undertaken in Kenya to examine the effects of various road, vehicle and environmental parameters on some components of vehicle operating costs. The investigation was undertaken jointly with the International Bank for Reconstruction and Development. The field work was carried out in two parts, i) an experimental study of vehicle speed and fuel consumption ii) a road user survey. The two studies are reported in separate sections and the results are combined to produce a set of relationships for estimating the effects of road geometry, surface condition, and vehicle age on the components of vehicle operating cost. All the components are defined in either quantity or non-dimensional terms and the actual cost is obtained by applying the appropriate unit cost prevailing at a particular time. The relationships derived from this study have been incorporated in the Road Transport Investment Model."
A Reservoir Model Alternative To The Unit Hydrograph For Flood Estimation
Abstract.
“A simple non-linear reservoir catchment model is described and compared to the unit hydrograph. Both models are calibrated using data from a Kenyan catchment. It is shown that the new model requires less data for calibration and is capable of more accurate flood prediction. The new model will be used for current flood studies in East Africa, and will be incorporated in the resulting flood estimation methods.”
A Study of Accident Rates in Developing Countries
Abstract.
“Using published data a study was made of changes in accident rates with time in a number of developing countries and it was found that in almost all the countries, there is a continuing downward trend in fatality and injury rates per vehicle, Kenya and Zambia being notable exceptions. Fatality rates were found to be related to vehicle ownership levels: the lower the vehicle ownership level, the higher the fatality rate per vehicle. In this relationship, vehicle ownership can be taken as an indication of both general economic and transport development. Fatality rates for the developing countries for the year 1968 were found to be similar in pattern to those for Britain between 1909 and 1938. The severity index, a measure of the number of fatalities as a proportion of total casualties, was found to be correlated with vehicle ownership levels: the lower the vehicle ownership level, the higher the severity index. A further examination of the severity index showed that it was closely affected by the extent of medical facilities in these countries. There was also some evidence that it was related to the proportion of motor cycles and scooters in each country. Possible methods of continuing road accident research in developing countries are suggested.”
Experience with The Fischer and Porter Vehicle-Counter under Tropical Conditions
Abstract.
“This Report describes operating and maintenance experience with the Fischer and Porter punched-tape counter under tropical conditions. It is based on the results of a two-year study by staff from the Laboratory of 25 counter installations in Kenya. The Report describes the special installation procedures required for earth and gravel roads. An analysis is given of the life of detector tubes and batteries and of the causes of counter breakdowns. The need for an underground method of detecting vehicles is clearly indicated by the difficulties experienced with conventional surface-laid pneumatic-tube detectors. The problems to be overcome in developing a viable system are discussed.”
The Relation between Soil Shrinkage and the Development Of Surface Cracks in an Experimental Road in Kenya
Abstract.
‘A commonly observed feature on roads in tropical countries is the presence of long cracks running parallel to the edge of the pavement. The mode of development of such cracks has been studied on an experimental road at the East African Agriculture and Forestry Research Organisation's estate at Muguga, Kenya. Measurements were made of the horizontal and vertical movements of the soil surface resulting from moisture changes. It was found that cracks occur along a line between the zone where there is a seasonal fluctuation of moisture content and the zone of more static conditions further under the pavement. It is suggested that the lateral shrinkage of the soil under the shoulder and edge of the road causes the systematic cracks to develop at the wet/dry interface in the subgrade. This interface is generally within 2 to 3 ft of the edge of the pavement and within the zone most frequently trafficked by the nearside wheels of road vehicles. The cracks provide an easy path for water to enter the road structure, hence such shrinkage cracking probably plays an important part in the behavior of roads in tropical countries.’
Measurement Of Pavement Deflections In Tropical And Sub-Tropical Climates
Abstract.
‘The measurement of the deflection of the surface of road pavements under a standard wheel load is common practice in many countries. The main purposes of making deflection measurements are to assist in the evaluation of the structural condition of roads, and to help in the design of road strengthening measures. In developing countries in the tropics the high road temperatures and other climatic effects necessitate the use of a special technique in making deflection tests. This report describes the techniques adopted by the Overseas Unit of the Transport and Road Research Laboratory for the measurement of pavement deflection in tropical developing countries, and discusses factors relevant to the deflection of road pavements in such conditions.’
The Compaction of Soils and Stabilized Base on Roads in East Africa
Abstract.
As part of a study of aspects of normal road-building practice in tropical countries, the states of compaction achieved in road bases and earthworks were investigated at ten road construction schemes in East Africa. In addition, where possible, controlled compaction trials were carried out. The most significant conclusion from the investigation is that the states of compaction achieved in the field correspond quite closely with those obtained in full-scale compaction tests carried out at the Transport and Road Research Laboratory. The relation between compactive effort, moisture content and the dry density obtained in the field followed accepted patterns; overstressing was noted on a uniform sand soil. The optimum moisture condition for compaction in the field was close to the optimum moisture content in the B.S. Compaction test 2.5 Kg (5.5 lb) rammer method, and simple and rapid methods of appraising the moisture conditions were effective in maintaining the moisture contents within an acceptable range. The study showed that the states of compaction commonly specified for tropical roads can be attained under normal working conditions.
An Analysis of Road Accidents in Kenya in 1972
Abstract.
"This report describes an analysis of the road accidents involving personal injury that occurred in Kenya in 1972. Nairobi Province was found to have the greatest number of accidents and casualties but the rates per million vehicle kilometres were lowest in this province. Fourteen per cent of all casualties were fatal which is a high fatality rate compared with countries in Western Europe and North America. This may be a reflection of the likelihood that in Kenya non-fatal personal injury accidents may not be as well recorded as fatal accidents. The proportion of all casualties that were occupants of commercial vehicles was very much higher in Kenya than in Europe. The number of accidents involving two vehicles were proportionately lower than in Great Britain whereas there were proportionately more vehicle-pedestrian and single-vehicle accidents in Kenya than in Britain. The incidence of single-vehicle accidents was particularly high in rural areas. Accident rates on murram (ie gravel surfaced) roads were found to be very high in relation to the volume of traffic carried by these roads."
Pavement Design on the Bulbul-Ngong Road
Abstract.
The natural subgrade beneath the existing construction was investigated at 10 chain intervals and samples of the material taken and tested. In situ, density tests were made in the existing construction, both at edges of the shoulders and against the tarmac edge. The positions of gravel deposits were investigated. An outcrop of basalt was located 2.5 miles from Ngong on the way to Kiserian and samples were taken from this for laboratory testing.
Inspection of Juja Road and Laikipia Air Force Base Road
Abstract.
Pavement evaluation was done by carrying out a detailed pavement defects survey where the defects were recorded and quantified. Improvement of drainage works was carried out. Stone pitched drains were upgraded.
Gravelling Programme in Kiminini Area
Abstract.
Thirteen quarries for gravel were investigated and tested with one existing quarry extended. The material site plans, test results and grading curves were drawn up. Further investigation of suitable gravel quarries should be carried out in the area to cover the remaining 47.5km.
Gravel Standard Pavement Design
Abstract.
Soil samples were a representative of the 3ft depth immediately beneath the organic top soil. The nearest hard rock source found was on the Manga Ridge.
Research on the repairing and resealing of roads
Abstract.
Pavement evaluation was carried out via visual assessment. A study of the maintenance history, measurement of the pavement’s bearing capacity and analysis of all pavement layers and surface through sampling and laboratory tests was conducted.
Traffic Flow and Pavement Evaluation on the London- Airport Road
Abstract.
Traffic counts were regularly carried out. A detailed survey to determine the influence of road junctions was done. Pavement evaluation was done through Benkleman Beam evaluation.
Geotechnical Investigation for Bridge Site
Abstract.
Drilling 2No. boreholes at the proposed new bridge site to a depth of 7.5m. Obtaining undisturbed samples in (U100) 100mm diameter tube samplers was carried out. Performing Standard Penetration Tests (S.P.T.) along the borehole depths was also carried out. The test results were then analyzed and preparation of factual reports.
Geotechnical Investigation for Footbridges
Abstract.
Three 3 No. boreholes were sunk. Undisturbed soil samples were each taken from each borehole where the soil strata allows and carrying out the relevant laboratory tests. Standard Penetration Tests (S.P.T.) was done in the boreholes. Water regime monitoring was carried out for the boreholes.
Investigations on the repairing and traffic growth on roads
Abstract.
To project future traffic growth, the Average Daily traffic (A.D.T.) data was collected. Benkelman beam deflections on all four wheel paths were also measured and pavement defects identified.
Investigations of Nginyang Bridge
Abstract.
Visual observation and tests. A total of nine locations were identified for ultrasonic tests for the beams. Three tests were done on each beam. Test locations were then core drilled for determination of core strength in the laboratory.
Stone Quarry sites in Nyeri
Abstract.
The sites were found along the Sagana, Kagumo and Gatitu Rivers, at places where the lava is outcropping in the valley side. The sites include Muruguru site, Sagana Power Station site, Ndunduguthu site, and Gatitu site. The stone from the sites investigated is a basalt, which is a hard dense lava. The Nyeri tuff is a relatively hard tuff.
Investigations on Early Road Failures
Abstract.
The roads were surveyed visually and early failures were observed. The exercise entailed walking on failed sections and driving a vehicle over the wholesome sections. The dimensions of critically failed sections were measured and special attention given to the possible causes of failures.
North Coast Stone Survey
Abstract.
The sites were investigated and the geological rock type was considered; listing worked sources or outcrops investigated and engineering properties. Preliminary stone samples were taken for laboratory testing. Igneous rocks in the Malindi Area were found in the Sabaki and Koroni valleys as well as east-north-east of Shakadula. In the Malindi Area Kambe limestone occurs east of the Mangea hills. The main areas where outcrops were met are in the Vitengeni and Sabaki valleys. In the Kilifi Area the limestone band stretches from North of Jaribuni to just north of Ribe. In Vitengani, there is an abundant supply of rock and possibly a site could be found which could be worked by quarrying methods. A string of quarries for Mariakani sandstone widely used as hardstone in the Coast region are worked along the Mombasa Road on the section Mariakani-Mazeras. The sites include Pentaguo, Chakama and Kinarani. Igneous rocks in the Malindi Area occur in Shakama D.C. Camp between Garashi and Baricho and on the north side of Baricho-Shakadula road. Some of the promising hardstone sites for surfacing quality stone are Chasimba, Pentaguo and Baricho.
Report on Pavement Failures & construction problems with GCS Base
Abstract.
A visual assessment was carried out. The contractor’s construction methods were reviewed. Samples from the field were taken and tested in the laboratory.
Re-evaluation of Rock Quarries
Abstract.
Satellite image interpretation including a visual study of false colour land sat images and interpretations of computer processed images. Photo geological interpretation of black and white contact prints aerial photographs. Field survey and material sampling were then done.
A study on Gravel Deposits for the Rural Access Roads construction Programme
Abstract.
A member of the overseas unit, TRRL, visited Kenya for two months to assist in the location of new gravel deposits for use in the programme for road construction. The services of a geologist with experience in air photo interpretation were considered. Mr. G Mutunga of the Materials Branch spent six weeks in the UK to receive basic instructions in air photo interpretation, to become familiar with the use of aerial photography in materials survey. Samples were taken from the field and tested in the laboratory.
Investigations on failure of Kakamega-Broderick falls road
Abstract.
Investigations on materials supplied was carried out. An analysis of properties of the mixture used in the premix was undertaken. The analysis of the laid surfacing obtained from sound and unsound sections was also done. Investigations on the Compliance of Consultants’ design with required specifications was reviewed before conclusions were made.
Assessment of the condition and proposals for remedial measures
Abstract.
Various data compiled to assess the condition of the pavement included:-A longitudinal cross section obtained from trial pits dug every 2km. In-situ and laboratory tests to assess the nature and strength of the pavement layers. Deflection values together with radius of curvature measurements. The deflection data was obtained from results of routine deflection measurement carried out in 1973/74 and further deflection measurement to elaborate on the data. The nature and extent of defects encountered on the road, which was done through visual inspection and through observation, and testing of cores from the road structure. Proposals for remedial measures were then given after analysis of results.
Study of Red Clay Highway Embankments with reference to Collapse and Cracking(1987)
Abstract.
The research involved carrying out laboratory and field tests to establish the cause of cracking and deformation of the highway embankments. The tasks included; monitoring the behavior of the selected road embankments, by way of periodic measurements of vertical and horizontal movements, using in-situ instrumentation; studying the characteristics of the material used in the construction of the selected embankments and comparison of the findings from the field and laboratory tests with the predicted values using theoretical models. Field experimentation involved installation of horizontal shrinkage gauges and leveling stakes in the selected embankments and monitoring the movements of the gauges and stakes. The laboratory tests were carried out on red coffee soils obtained from the side slopes near the cracked embankments of the test sites. The results were then analyzed.
Problems of Red Coffee Soils in Kenya
Abstract.
Both the disturbed and undisturbed soil samples were collected from twelve different sites of Nairobi. It was noted that long storage in the laboratory or in open air may alter the properties of some residual soils, and for this reason all soil samples tested were collected and tested within three months of collection. All the tests were done as per BS 1377 1975 code. Conclusions were made from the analysis of the results.
The TRRL road investment model for developing countries (RTIM2)
Abstract.
"A computer model is described which is designed to aid investment decisions within the roads sector in developing countries. The model calculates the construction cost of a road and predicts the condition of the road as time passes and vehicles travel over it. Having predicted the condition of the road, the model estimates the costs of road maintenance and the cost of operation of the vehicles for each year. All these costs are then discounted back to the base year and summed over the life of the road to obtain the total cost. All estimates are made in terms of physical quantities and costs are obtained by applying unit rates to these quantities. The results of a study in Kenya were used to calibrate a prototype version of the model. This prototype was tested extensively for the appraisal of road projects in developing countries. As a result of this experience, the model has now been reprogrammed to make it easier to use and to fit onto smaller computers. The opportunity has also been taken to include in the model the results of the latest research in developing countries in this field carried out by TRRL. The relationships built into the model allow it to be used to study the interrelationships between road design and construction standard, road maintenance policy, vehicle characteristics, traffic flow and growth rates, environment, and road deterioration. The model can be used to study various aspects of a road investment project such as the optimum maintenance standards for the road, the effects of providing an earth, gravel or bituminous pavement, Or the differing benefits that can be obtained by adopting various stage construction options. The model will also allow the planner to study the consequences of uncertainties in traffic forecasts or in the discount rate."
A road transport investment model for developing countries
Abstract.
“The Report describes the development of a model which can be used to aid investment decisions within the roads sector in developing countries. The Report is aimed at senior administrators, engineers and planners and at those responsible for developing improved techniques for road investment appraisal. The model calculates the construction cost of a road and predicts the condition of the road as time passes and vehicles travel along it. Having predicted the condition of the road, the model estimates the costs of road maintenance and the cost of operation of the vehicles for each year. All these costs are then discounted back to the base year and summed over the life of the road to obtain the total cost. All estimates are made in terms of physical quantities and costs are obtained by applying unit rates to these. The model is very flexible and can be used to study the economics of varying stage construction alternatives such as, upgrading an earth road to gravel or paved road at any time during the design life. The Report describes the construction, road deterioration, road user cost and road maintenance sub-models and then looks at a case study of a road in Kenya.”
A study of household travel in the Meru District of Kenya
Abstract.
Data was presented on household income levels, the incidence and purpose of household trips, travel costs and the elasticity of the demand for travel. The household travel study relied on a panel survey methodology in which 300 households in twelve village areas were randomly selected for interview in 1983. This baseline survey collected household socio-economic data and compiled a record of household travel over a four week recall period. The two subsequent surveys in 1986 and 1989 collected similar information from 291 and 283 households respectively within the original sample. The analysis of the surveys was done; this was presented in four sections: i) The first examined the geographical and economic basis of household income in the study area. This analysis used the core of 283 households common to the three household surveys. ii) The second examined travel purpose and the patterns and level of household travel before and after road improvements. iii) The third assessed the changing relationship between household income, travel costs and propensity to travel. iv The fourth gave estimates of the elasticities of demand for travel derived from cross-sectional and longitudinal analysis
Car Ownership and use in Kenya
Abstract.
“As part of a study to examine transport policies to conserve energy, surveys on car ownership and use were carried out in four urban centres in Kenya during 1981. Data on household characteristics and car ownership were collected in a series of workplace interviews. Respondents from households which owned a car were asked to compile a journey log for one week to provide a detailed record of their car use. Car ownership was found to correlate well with household income according to a quasi-logistic relationship. The report examines single and multi-car ownership and the effect of household income on the type of vehicle owned. By comparing ownership data with similar data collected in 1970, conclusions are drawn about trends over time. Car travel and occupancy are analyzed by income group and journey purpose and implications of the results for fuel conservation policy are discussed. ”
Effect of prices on petrol and diesel sales in Kenya
Abstract.
"To assess the effectiveness of fuel pricing as a means of controlling fuel sales in Kenya, time series analyses were carried out to quantify the effect that changes in price have had on sales of petrol and light diesel fuel between 1972 and 1981. While sales of both products correlated well with time or GDP, it was found that a GDP-based model gave more consistent results and that price had only a small effect on sales. Short-term price elasticity appeared to be around -0.1 for petrol and close to zero for diesel. The difficulty of measuring long-term price elasticity is discussed. It is concluded that taxing fuel is an effective way of collecting revenue but an ineffective way of controlling fuel sales in the short term."
The Kenyan low cost modular timber bridge
Abstract.
"A novel design of a type of timber truss bridge that has been developed in Kenya is described. The bridge comprises a number of identical timber frames that are assembled into trusses of the required span. Two or more parallel trusses are supported on conventional abutments, and the timber deck rests on top of the trusses. Loading tests carried out on individual frames, on groups of frames, and on complete bridges, have indicated that the design is suitable for bridges ranging in span from 12m to 24m required to carry limited numbers of vehicles up to 20t gross weight provided that the deck is accepted as contributing to the structural strength of the bridge. This assumption would not normally be made for bridges of this kind, but in practice, measurements show that the deck does contribute significantly to the strength of the bridge. In lightly loaded situations, provided regular maintenance is undertaken, the bridge can be expected to have a life of 20 years. Evidence of the durability of the bridge at higher traffic loadings is not available. The cost of the bridge in Kenya is between one-half and one-fifth of comparable steel or concrete bridges."
Vehicle operating costs in the Caribbean: an experimental study of vehicle performance
Abstract.
"This report describes an experimental study of vehicle speed and fuel consumption undertaken in the Eastern Caribbean island of St Lucia. The study was designed to extend the range of the empirical relationships derived in an earlier study in Kenya which relate vehicle speed and fuel consumption to the geometric characteristics and surface condition of the road. The results of this study are compared with the relationships derived in the Kenya study and recommendations are made on the use of the two sets of relationships. A methodology has been evolved to provide vehicle speed estimating relationships which are applicable to physical and environmental conditions lying between the two sets of conditions encountered in Kenya and St Lucia. The relationships derived from this study have been incorporated in the TRRL Road Investment Model for developing countries (RTIM2)."
Tensile And Compressive Strength Of Some Stabilized Road Bases In Kenya
Abstract.
"This report describes the measurement of the direct tensile and unconfined compressive strength of samples cut from stabilized road bases in Kenya. The test methods used are described, and the strength of the samples is compared with the performance of the roads. The report concludes that although the bases have lost tensile strength in service, they have not suffered serious structural damage and with routine maintenance these pavements should continue to perform satisfactorily."
Deflection-Temperature Relationships For Bituminous Road Surfacings In Kenya
Abstract.
"Details of deflection-temperature relationships are given for bituminous surfacings up to 150 mm thick on Kenyan roads. On some sites plastic deformation of the bituminous surfacing was identified during deflection tests at relatively low temperatures. However valid deflection measurements could be obtained on other sites at surfacing temperatures up to 60°C. Hardening of the bitumen in the surfacing was monitored and found to have a significant effect upon deflection-temperature relationships. No general corrections for deflection-temperature relationships could be formulated because the relationships vary even within 100m long sections of road. It is concluded that it is necessary to undertake deflection-temperature tests when carrying out deflection surveys on roads containing bituminous materials in tropical environments."
Performance of Sections of the Nairobi to Mombasa Road in Kenya
Abstract.
"Details are given of the performance of sections of the Nairobi-Mombasa road in Kenya. Nine sections of road with cement-stabilized bases surfaced with multiple seals, and three sections with crushed rock bases and asphaltic concrete surfacings have been studied for seven years. These road sections are located in a dry area, on strong subgrade soils. It was found that the lightly constructed sections with cement-stabilised bases had suffered little structural damage after carrying 6 x 106 equivalent standard (80 kN) axles, considerably more than would be predicted by current methods of pavement design. The more heavily constructed sections with asphaltic concrete surfacings are performing broadly as would be expected. For both types of pavement, deterioration has been mainly confined to the surfacings, and timely resealing has a powerful effect in limiting the amount of patching required and in maintaining an acceptable level of surface roughness. The lives of the better quality seals have been of the order of four to five years. Deflection measurements clearly show how variations in overall pavement strength are affected by changes in annual rainfall, and the wide variation in strength which can occur on a nominally uniform pavement. Deflection measurements did not give early warning of pavement surfacing failures."
Axle-Loads on Paved Roads Kenya
Abstract.
“This report describes a study of the traffic loading on the paved primary roads of Kenya. The study formed part of a major field investigation designed to provide relationships for a computer model capable of estimating road construction costs, maintenance costs and vehicle operating costs. The work described in this report comprised part of the engineering investigations into the relationship between pavement damage and axle loading. Most of the work was carried out on the experimental sites of the main study. Additional surveys were conducted on sections of the proposed Trans-African Highway route not covered by the study, together with sites on the South Coast Road which carries heavy traffic between Zambia and Mombasa. On the major route in Kenya the average damaging factor of commercial vehicles was found to be more than ten times greater than that of similar vehicles on motorways in U.K. The surveys were carried out during the period 1971-1974.”
Forecasting Rural Road Travel in Developing Countries from Studies of Land Use
Abstract.
“In many developing countries, the difficulty of standardizing trip measurements, the flexibility with which vehicles are used and the absence of a conventional sampling frame for interviewing road users are the main obstacles to forecasting travel from land use. A study in Kenya has shown the difficulties of using roadside interviews for establishing trip relationships, but has indicated that a suitable sampling frame could be constructed by a direct survey of vehicle owners. The vehicle owner in the broadest sense would then become the fundamental unit for trip studies. The Report suggests that home and workplace questionnaire surveys, focusing on the vehicle owner, may be suitable for the extensive sampling necessary to evolve standards for studies of rural trip characteristics. Definitions of employment suitable for land-use/transport studies in developing countries are suggested in the Report. These covered only 4 per cent of the population of the study area, but nevertheless, statistically they provided the best explanation both for vehicle ownership and for trip generation. Trip origins from Agricultural and Residential land uses did not reach significant proportions. The main generators were Retail and Commercial, Road Transport, and Government Administration land uses, which together accounted for over 75 per cent of urban trip origins and 57 per cent of all trip origins.”
A Study of Accident Rates on Rural Roads in Developing Countries
Abstract.
“The purpose of the study described in this report was to investigate relationships between personal injury accident rates on rural roads in Kenya and Jamaica and factors such as vehicle flow and road geometry. Regression analysis was used to derive equations which can be used to estimate changes in accident rates following improvements to the geometric design of the road. The accident rate per kilometre per annum was found to be significantly related to the vehicle flow whilst the rate per million vehicle-kilometres was found to be significantly related to the physical characteristics of the road tested, such as junctions per kilometre, surface irregularity and road width. Comparisons were made with similar relationships derived in a number of developed countries; the accident rates in Kenya and Jamaica were found to be consistently greater for similar values of vehicle flow and geometric design.”
Tables for Estimating Vehicle Operating Costs on Rural Roads in Developing Countries
Abstract.
"Tables are provided for estimating vehicle operating costs by component on free-flowing low volume rural roads in developing countries. They provide a convenient and easy reference manual for road appraisal and investment studies. The components evaluated are fuel and oil consumption, maintenance parts and labour charges, tyre wear, depreciation, crew costs and standing charges. They are estimated on a quantity or non-dimensional basis so that costs can be determined for any monetary system or environment by applying the appropriate set of unit rates. Operating costs may be estimated for different road geometries, surface condition and altitude and for vehicles of different types with different prices, ages, loads and engine power. The tables are based on research carried out in Kenya by the Overseas Unit of TRRL in collaboration with the International Bank for Reconstruction and Development."
The TRRL East African Flood Model
Abstract.
"Four years of data from 13 small representative rural catchments in Kenya and Uganda were analyzed to develop improved methods of flood estimation for highway bridges and culverts. Due to the short period of record and the very quick response time of the catchments, Unit Hydrograph techniques were found inappropriate. A technique which made better use of limited data, therefore, had to be developed. Rainfall and runoff were fitted to a simple three parameter conceptual catchment model. The model was then used to predict the 10 year flood using a 10 year design storm. A simple technique is then developed for predicting the peak flow and base time of design hydrographs for ungauged catchments."
Road Transport Research Bodies
© 2021. Kenya Roads Board Knowledge Centre