Proceedings of the international conferences on the bearing capacity of roads, railways and airfields
Background and Scope The main objective for the BCRRA conference is to promote efficient design, construction and maintenance of transport infrastructure by addressing issues related to bearing capacity problems of roads, railways and airfields. Bearing capacity issues are continuously changing as traffic volumes and weights increase, new materials and methods are developed, and new aspects of design and material utilization are brought into focus. In this context there is an increasing need for a forum where experts in this field, from all over the world, can exchange views and experiences, and discuss new concepts and innovative solutions. The BCRRA conference aims to provide such a forum.
Norwegian University of Science and Technologhy
Typical drainage problems in Northern Europe and the effect of improving drainage
Typical drainage problems in the Northern Periphery area of Europe have been addressed in this paper. Field observations for roads on sloping ground shows large differences in rut depth and roughness on the road cut side compared to the embankment side. The road cut lane has the ground water table much closer to the road surface and therefore also a higher moisture content in the road structure materials and the subsoil. For 20 % of the analysed roads the rut depth on the road cut lane is 1.5 times larger than on the other lane. Just 12 % of the roads have larger rut depth on the embankment lane. Predictions models are used to demonstrate the change in lifetime (calculated as number of standard axles) as a function of moisture content. Both field observations and prediction models show that improving the drainage will give a large profit in lifetime and also the life cycle costs. These are calculated for a period of 50 years and the conclusion is that maintaining and improving the drainage system is cost effective and must be prioritised among other maintenance activities. The first step in strengthening a road should be to make sure that the drainage system work properly and should be improved 1-2 years before paving.
Copyright (c) 2005 Geir Berntsen, T. Saarenketo
Monitoring and Classifying Spring Thaw Weakening on Low Volume Roads in Northern Periphery
The ROADEX II Project is a co-operation aimed at developing ways for interactive and innovative management of low traffic volume roads in the Northern Periphery Area in Europe. The goal for subproject 2.3 “Spring Thaw Weakening” was to collect information regarding one of the most difficult challenges in low volume road condition management in cold climate areas, managing road condition during the spring thaw weakening period in a way that minimizes the impact of transportation problems on local livelihoods without destroying road structures or reducing the service level of the road for the rest of the year. The survey has followed the Roadex II Project phase II theme of “understanding and analysis” by using new technologies to monitor spring thaw problems and then analysing the problem sections so as to better understand the processes behind the problems. Data collection for monitoring the seasonal changes and spring thaw weakening was done at five test sites in Scotland, Sweden and Finland. This paper presents a summary of the field tests and, based on these results, proposes a new classification for spring thaw weakening periods and typical spring thaw damages that can happen during these periods. This helps engineers to better focus on the problems and find more economical and sustainable solutions in managing spring thaw problems in their low volume road networks.
Steel Grids, an Efficient Way to Improve the Durability of the Pavement
A synthesis of the test results with steel grids in trial road constructions was made in the so called STEELSYNT project. The material for this synthesis has been: the TPPT (Pavement Structures Research Programme) test constructions, the European reinforcement research programme called Reflex and some HVS test projects. HVS (Heavy Vehicle Simulator) is a mobile accelerated loading test facility. All test results both in laboratory and in field conditions showed that rutting can be remarkably reduced by using steel grids in bitumen bound layers or unbound base. In average this reduction lies between 40 - 60 %. The reinforcement works best in the cases where the bearing capacity of the pavement is low. A steel grid prevents the development of longitudinal frost cracks in the reinforced area. The longitudinal cracks usually move to the edges of the road where the grid ends. Steel grid also mitigates the transverse frost cracking by curtailing the width of the cracks and by preventing the development of small cracks. The test results showed also that steel grid delayed fatigue to some extent. The Reflex project prognoses that reflection cracking of the cement bound gravel base can be reduced 35 % by steel grids. The studies so far have not found that longitudinal unevenness could be levelled with reinforcements. Falling Weight Deflectometer is not a suitable measurement tool to quantify the improved performance of a reinforced pavement, so new methods are needed.
Copyright (c) 2005 L. Korkiala-Tanttu, H. Rathmayer
Due to the increase of heavy traffic loading and expenses for road maintenance and rehabilitation a continuous research and development work in the field of innovative pavement and material designs is needed. Aims of reinforcement structures used in asphalt roads are prolongation of service life by increasing bearing capacity and delaying plastic deformations or cracking respectively. Within the 4th EU-framework the REFLEX-project “Reinforcement of flexible road structures with steel fabrics to prolong service life”, was focusing on benefits and further developments of reinforced asphalt layers using steel fabrics. Dependent on the load and environmental conditions within Europe the research group was focusing on bearing capacity and on resistance against thermal cracking (including frost heave) reflective cracking, plastic deformations and flow rutting. This paper shows the German investigations, results and experiences focusing on flow rutting and bearing capacity: - Design of reinforced pavements supported by theoretical models (Multi-layer-theory, FEM) to check the performance of net structures. - Interaction between asphalt and reinforcement structures (bond) as well as performance of reinforced layers by lab tests. - Monitoring of the behaviour of steel reinforcements during the placing of the asphalt and establishment of recommendations for the design and the construction of such pavements. Measurements performed during the paving process show the sensitivity of this technology (especially for the usage against flow rutting) given by the fundamental material properties of asphalt and steel. - Monitoring of test sections (especially bus-stops) and road sections.
Geosynthetic Material Properties for Use in 2-D Finite Element Pavement Response Models
Modern finite element response models for flexible pavement analysis and design are traditionally two-dimensional axisymmetric models. The inclusion of a geosynthetic reinforcement layer in such a model is generally accomplished by the insertion of a horizontal layer of membrane elements. These elements are particularly well-suited for describing geosynthetics in that they carry loads in tension while having zero bending stiffness. The use of a 2-D axisymmetric response model requires that the reinforcement be described by an isotropic material model. Geosynthetics commonly have direction dependent properties, the most notable being an elastic modulus that differs between the machine and cross-machine directions of the material, which are described best by an orthotropic constitutive model. This paper presents an approach that allows a geosynthetic’s orthotropic linear elastic properties to be converted to equivalent isotropic linear elastic properties for use in 2-D finite element response models. This is accomplished through a work-energy equivalency equation developed from a general stress application to a geosynthetic material modeled by an orthotropic and an isotropic linear elastic sheet. Parameters contained within the equation are calibrated by the comparison of pavement response of a completely 3-D finite element model containing a geosynthetic having an orthotropic material model to a 2-D finite element model having an isotropic material model for the geosynthetic. The study results in a simple equation to convert orthotropic properties to equivalent isotropic properties.
Copyright (c) 2005 Steve W. Perkins, Gudmund Eiksund
On design principles of reinforced pavement structures - the COST 348 REIPAS action
The paper is summarizing the development work for reinforcement of pavements and structures in the COST 348 REIPAS Action. Design approaches developed either for the utilization of geosynthetic reinforcement materials or for the utilization of steel grids are referred. The basic common principles of reinforcing practice is inserting or laying the steel or geosynthetics mesh below or underneath the pavement either during the maintenance or reconstruction of existing roads or construction of new sections. The COST 348 action is taking a step towards practicable guidelines for the structural design and execution of reinforced pavements and road sub-bases and to reach a consensus on the methods to determine relevant material parameters essential for analysing or predicting the behaviour of the reinforced structures.
Copyright (c) 2005 H.G. Rathmayer, L. Korkiala-Tanttu, Arnstein Watn
EXPERIENCE FROM MORE THAN 30 YEARS OF ASPHALT REINFORCEMENT WITH POLYESTER GRIDS
Reflective cracking is a well documented and known phenomenon. Without any treatment cracks and/or joints in existing cracked pavement structures will propagate nearly vertical through a new asphalt overlay, creating a reflective pattern similar to the one existing before. The prevention of reflective cracking in pavements has always been an area of concern when designing for asphalt concrete overlays. A very effective system for the delay or even complete arrest of reflective cracking has proven to be Asphalt Reinforcing Geogrids made out of Polyester fibres, which have successfully been used for about 35 years now. Reinforcements have been successfully used in different applications as roads, highways and airports in nearly all climatic conditions. Examples of evaluations in various countries and conditions are given. Also a number of laboratory studies have been performed on reinforced asphalt systems. The goal of most studies was to simulate the actual load condition of a cracked pavement. When a wheel passes a crack the system is stressed dynamically in different modes (bending and shearing) depending on the wheel position. Additionally horizontal movements may occur due to temperature variations. The results of the studies will be summarised. Special attention is also given on the performance on site, such as the installation process, milling of reinforced asphalt and the reuse of recycled reinforced asphalt.
Permanent Deformation Behaviour of Low Volume Roads in the Northern Periphery Areas
Roadex II has been an EU financed research project concentrating on the maintenance of the low volume road network in the Northern parts of Finland, Sweden, Norway and Scotland. One of the aims in the Roadex II project has been to assess the permanent deformation behaviour of the low volume roads in these Northern periphery areas especially for the purposes of finding efficient and cost-effective means of maintaining the structural condition of the road network with as little disruption as possible to the vital heavy transports of the forest and fishing industries and agriculture. This paper presents a tentative approach for estimating the risk of permanent deformations in a low volume road and the need for weight restrictions especially during the thawing period of seasonal frost. The assessment is based on a monotonic and repeated load triaxial test series performed at the Tampere University of Technology in Finland and at the University of Nottingham in the UK. The results of these tests have been interpreted using a non-linear finite element analysis to compute the likely plastic strain in the pavement and, hence, the risk of rut development, and a simplified approach proposed for routine use.
Copyright (c) 2005 A. Dawson, P. Kolisoja, N. Vourimies
Application of Advance Pavement Technology for Airfield, Field Experience at Kuala Lumpur International Airport (KLIA)
The basic requirement for civil engineering materials construction usage is to use and optimise readily available materials nearest to the work site. Dependency on imported technology can sometimes limit the application of good engineering materials. Working from first engineering principles supported by research is a productive method to use non-standard materials confidently under known local environment. The pavement works at the KLIA underwent thorough studies working from basic principles. These principles are fully deployed during planning, design and construction in line with the available materials. Advanced technology was adopted for the design and construction while new materials were introduced for construction. This paper describes the historical and technical development of the pavement studies under local conditions, design and construction at KLIA. The pavement used stabilize meta-sandstone base as a structural bearing layer. The surfacing layers comprises of the bituminous crack relief layer (CRL) overlaid by polymer-modified asphalt (PMA). All these layers were newly introduced and were applied for the first time in large quantities in Malaysia. After five years the technology used had shown the expected performance even though the loading condition increased. The incorporation of a pavement management system in the monitoring exercise is also described. Valuable lessons learned from the starting point of investment up to maintenance management stage is described to guide investors on optimum use of pavement technology to benefit all stakeholders.
Copyright (c) 2005 M. S. Hasim, Z. Ahmad,, S A Ghani,, A H M Ali, M A M Amin, A M A Hameed
The rehabilitation of roads is not a simple task. This process requires systematic techniques to evaluate the current state of the road as well as techniques to select the most plausible reinforcement works. This work describes the studies and evaluation process to rehabilitate a highway located in the east access of the city of Guadalajara, the second largest city in Mexico. Particularly, the works focused on the left body of the Zapotlanejo- Guadalajara highway which experiences high volumes of heavy transit. The recycling technique was chosen to reinforce the highway. The recycling works uses recovered material in the formation of the hydraulic base as well as the material used in the asphalt surface of the new pavement. This paper describes the works performed before the rehabilitation works. These works include the results of the superficial evaluation, the structural analysis, the reinforcement design, the constructive procedure, and the performance studies covering ten years of successful operation of the highway.
Copyright (c) 2005 E. Padilla, G. Padilla
Laboratory and Field Testings of the New Concrete Friction Sleeper
In summer the temperature stresses in the rails may become very high and induce lateral distortion of the track with risk of derailment. In small radius curves (R < 300 m) there are restrictions on use of CWR due to the risk of track buckling. This requires fishplated rail-joints with their many drawbacks. To improve safety and reduce maintenance costs it was found essential to find a practical way of improving the lateral resistance of ballasted track with concrete sleepers. The new concrete Friction Sleeper was designed with cross-wise ridges at the under-side to form a coarse cogging with adequate dimensions to utilise more of the high internal friction potential of the crushed stone ballast. By lateral displacement of this sleeper a completely continuous layer of ballast material will be held fixed to the sleeper under-side by hooking, wedging and granular interlock, and give a very high friction resistance. In performed field tests the Friction Sleepers provided a considerably larger lateral displacement resistance than the standard concrete and wood sleepers. Based on the observation data in these tests, the track with Friction Sleepers obtained the highest absolute and relative lateral resistance values for all three axle load levels. A very important result was that the unloaded track with Friction Sleepers had a very high lateral resistance, 35 and 110 % higher than obtained by the track with the standard concrete and the wood sleepers respectively. Based on the field and laboratory test results the new concrete Friction Sleeper has a considerable potential to yield higher safety against rail buckling, increased use of CWR tracks and less strict requirements on ballast quality and ballast profile.
Copyright (c) 2005 R.S. Nordal, A.H. Løhren
Development of a Hi-Soft Asphalt Pavement for Cold Regions
Through structural evaluation and performance prediction, a new type of asphalt pavement was developed, based on 3 years of laboratory and in-situ tests. It is named a Hi-soft Asphalt Pavement, HIHSA in short due to its characteristics of being more flexible, and more adaptable to deformation and bearing capacity defects of the roads, etc. As the recent research findings from a research project financed by the Ministry of Communications, P.R. CHINA, HIHSA is more suitable for low volume roads in cold regions. During the development, the researchers highlights the use of local materials such as the naturally crushed stone accumulated in mountain slope, the river gravels and others, to the largest extent for wearing course, base-course and subgrade. And due to no need to heat at high temperatures for both aggregates and binders comparing with hot–mix asphalt, less low temperature cracking, easy recycling and maintenance, HIHSA is also very cost-effective. 11 different kinds of pavement materials and structures were chosen for the test road, which is located in the northern-most China’s Daxing-anling Region. According to in-situ observations and experiments on bearing capacity, frost heave, cracks and other defects, and others, in connection with lab tests and structural calculation and analysis, Specifications for HIHSA Pavements’ Design, Construction and Quality Control were worked out for further wide application in other northern and western provinces and areas.
Copyright (c) 2005 X. Wang, J. Ji, M. Wang, C. Chang, X. Gao
Study of a Rehabilitation Method with a Pavement Reinforcement System for Low Volume Roads
This paper presents the first results of an experimental study aimed at evaluating the effectiveness of a rehabilitation method for low volume roads. The method suggests the usage of a steel reinforcing netting in order to improve the performance. It consist in reconstructing the surface layer placing a steel reinforcement in the interface between the new binder layer and the existing base course. This reinforcing method aims at making a road possibly support a sudden increase of number and load of vehicles quickly and with a modest maintenance. The research considered the problem from three points of view: real scale, by constructing and monitoring an experimental section; reduced scale, with laboratory tests reproducing the situations recorded in the experimental section; a finite element modeling using all the so gathered results. The findings show that although the steel netting is placed in the top layers of the pavement, it is still able to improve its resistance and its strain energy absorption ability consequent to the vehicles transit.
Copyright (c) 2005 A. Montepara, G. Tebaldi, A. Costa
Observations, Analysis, and Prediction of Asphalt Cracking
The various causes/categories of pavement cracking and generalized criteria for identification of potential deficiencies are presented in conjunction with case histories that relate to investigations of pavement distress. Asphalt binder properties, such as viscosity and penetration are shown to relate well with thermal and combined thermal/load stress conditions. Although slightly more involved testing procedures are required, criteria have been developed for different yearly ESALS to identify a paving mixture’s resistance to top-down cracking. Dissipated creep strain energy parameters are obtained from indirect tension tests to define an energy ratio for separating cracked from uncracked pavements. It is difficult to interpret Falling Weight Deflectometer (FWD) data from cracked pavements unless special procedures are followed. At high pavement temperatures the influence of cracks will diminish and allow for improved determination of moduli for underlying pavement layers and foundation/ subgrade soils. These analyses are enhanced when asphalt viscosity relationships with resilient moduli are used to assign E1 values for backcalculation. Relationships or procedures for estimation of any pavement layer or subgrade modulus are very beneficial in simplifying the interpretation or backcalculation of other layer moduli. Where possible, laboratory test parameters that relate directly to the behavior of paving mixtures should be integrated in the design and performance models for asphalt pavements. Realistic, multiple/simplified, methods for design and/or evaluation of pavement performance are desirable over one specific approach since comparable results are an indication of reliability.
Copyright (c) 2005 M. Tia, R. Roque,, Byron Ruth
Results of a study on Environmental Practices and Regulations
Growing interest in the environment in today’s society has led to increasing focus on environmental issues. This also applies to the road sector. By its very nature, this sector involves appreciable loading on the environment, so there is every reason to take active measures to achieve more environmentally appropriate operations. Appreciable gains can be made, environmentally as well as economically. The major environmental loading from the road sector originates principally from the exhaust gases and emissions from road traffic, although road building, rebuilding and maintenance of the road network also can cause significant environmental impact in certain cases. This paper is a part of the ROADEX II project.
Road Construction on Soft Soils in Indonesia: A Study on Soil- Pavement Interaction
The soft soils area in Indonesia covers about 10 million hectares or 10 % of the total land area. Because of the low bearing capacity and high compressibility of the soft soils, many roads in this area lose their serviceability before the end of their original design life. One of the causes is that due to the lack of thorough understanding of the behaviour of the soil and its influence on pavement performance, no optimum maintenance measures are carried out. This paper presents a case study of a road on a soft marine clay subsoil in Cilincing, North Jakarta, Indonesia. The road was built in 1980 and since that date many severe structural damages in the pavement occurred due to uneven settlement of the subsoil. To investigate the effects of uneven settlements on pavement response, the finite element method was utilized on a large scale in this study. From an extensive series of analyses, which included uneven settlements as well as traffic loadings, it can be concluded that an integrated soil/pavement analysis provides a much better understanding of the interaction mechanism between pavement and subsoil.
Copyright (c) 2005 R. Taufik, A. de Bondt, W. van Bijsterveld, P. Thé
Socio-Economic Impacts of Road Conditions on Low Volume Roads
Traditionally the road conditions on low volume roads have been neglected. The main reason is the economic resources, which are insufficient to cover all the needs. But there are also other reasons why the low volume roads are kept back in the road maintenance programs. Used socio-economic models to describe the maintenance need, normally deal with road user costs consisting of time delay costs, vehicle costs and accident costs. But as the amount of traffic always is the dominating figure in the calculations the models will favour a very good condition on high volume roads and only keep the low volume roads alive. That will give the highest benefits for the society with the existing models. To change this, in order to give people living in rural areas better life conditions, there is a need for a new thinking to find alternative ways to describe the significance in having good road conditions especially in the rural areas. The first thing is to look at socio-economic impact in a wider meaning. There is a need to take a closer look at the social improvements for people living in rural areas if the road conditions are improved. Secondly there is a need to look at the health impacts, especially for professional drivers, if rural roads are left to deteriorate. By a literature survey, meetings and interviews with skilled people from Sweden, Finland, Norway and Scotland it is found how the socio-economic impacts are considered today by the road managers and what is going on for the future. The report will describe briefly the models used today, some calculations done with a Swedish model, work done and going on to improve the road conditions on low volume roads in the partner countries and in what way the road condition may affect personal health for road users.
Dealing with poor bearing capacity on low volume roads on peat in the Northern Periphery
The Roadex II project is an EU funded trans-national technical co-operation between the northern European roads districts of Finland, Norway, Sweden and Scotland whose main aim is the sharing of technical information and good practice. The goal of subproject 2_5, ‘Dealing with Bearing Capacity Problems on Low Volume Roads Constructed on Peat’ was to gather together existing and past practices for dealing with bearing capacity problems for roads constructed on peat in the Partner roads districts, with particular reference to lightly trafficked roads. As part of this exercise interviews were held with practising roads and geotechnical engineers in the Partner areas to gain as full an insight as possible into their current thinking. The result of the research is a snapshot of the Partner area practices in dealing with bearing capacity problems in roads constructed over peat that covers such topics as the classification and engineering properties of peat, local field survey methods, testing, design considerations, risk management, methods of construction supplemented by local case studies. This paper gives a summary of the research carried out within the Partner areas and offers a ‘snapshot in time’ of local thinking for dealing with bearing capacity problems on low volume roads constructed on peat.
Factors Affecting Laboratory Rutting Evaluation of Airport Pavement Granular Layers
This paper presents research findings on characterizing and predicting the permanent deformation behavior of airport pavement granular base/subbase layers constructed and tested at the National Airport Pavement Test Facility (NAPTF) in the United States. The P209/P154 aggregate materials were used in the construction and testing of the NAPTF flexible pavement test sections with variable thickness base and subbase courses. To account for the rutting performances of these substantially thick granular layers, a comprehensive set of repeated load triaxial tests were conducted in the laboratory on the P209 base and P154 subbase granular materials. Based on the laboratory test results, mathematical models were developed to predict maximum permanent deformations occurred under both 6-wheel and 4-wheel gear loadings applied following a wander pattern. The performances of the developed rutting models were evaluated for predicting the field accumulation of permanent deformations by properly taking into account the NAPTF trafficking data and the previous loading stress history effects. A comparison of the measured and predicted permanent deformations indicated that a good match for the measured rut magnitudes and the accumulation rates could be achieved only when the magnitudes and variations of stress states in the granular layers, number of load applications, gear load wander patterns, previous loading stress history effects, and trafficking speed or loading rate effects were properly accounted for in the laboratory testing and permanent deformation model development.
Copyright (c) 2005 Erol Tutumuluer, In Tai Kim
Structural Evaluation of a Pre-stressed Concrete Airport Pavement
This paper concerns the assessment of the bearing capacity of a pre-stressed concrete airport pavement built in the 60’s, using non-destructive tests complemented with a number of other in-situ and laboratory tests aiming at the characterisation of the stress state in the concrete slab 40 years after construction. The work performed comprised visual inspection, FWD tests, core drilling and site investigation, “small flat jack” tests (normally used in rock mechanics), as well as the characterisation of the in situ stress condition of the pre-stressing wires. A finite element computer program was used, together with multi-layer computer programs, for modelling the pavement, taking into account different friction conditions at the interface between the concrete slab and the soil-cement sub-base. The paper describes the methodology used in the study and presents some of the results achieved.
Copyright (c) 2005 M.L. Autunes, J.J.C.B. Veloso, S. Fontul
New Material Treatment Technologies in Management of the Effect of Seasonal Variations
In the recent years, it has been considered more to use lower quality aggregates in road construction. This has become necessary mostly due to smaller supply of good quality materials available within a reasonable transportation distance and higher transportation costs. Nontraditional stabilisers have been marketed as economical and promising to improve the properties of poor quality materials. In the regions with long frost periods, such as S candinavia, open-graded aggregates containing a small amount of fines have been used in road construction in order to prevent frost heave. As fines content increases, the moisture susceptibility of aggregate becomes greater, leading to problems with bearing capacity in spring when frost thaws. The research was done to find out if non-traditional stabilisers would provide a toolbox for decreasing the moisture susceptibility of coarse-grained aggregates having, except for spring-time frost thawing, a sufficiently good bearing capacity. Polymeric and ionic stabilisers and resins have been tested. This paper presents the effects of the stabilisers on four different aggregates. The laboratory research consists mainly of Tube Suction tests. The literature studies and test results indicate that ionic and enzymatic stabilisers can hardly be used for decreasing moisture susceptibility in aggregates having a fines content of less than 15%. The tests showed that polymeric stabilisers and resins were the most promising stabilisers. It must be noted that the same stabiliser might act in a different way from one aggregate to another. Therefore it should always be checked whether the stabiliser is applicable in connection with the aggregate in question.
Copyright (c) 2005 N. Vourimies, P. Kolisoja, T. Raitanen
Evaluation and Rehabilitation of Composite Pavement on Motorway Network in Serbia
In the eighties the pavements on motorway roads were built with the sub-base layer made with high strength of cement-treated aggregates. After a period of considerable fall of transit traffic and lack of maintenance ensued from the political isolation of the country, by the beginning of new century the transit traffic was returning on "arterial" road facilities in Serbia. This period was marked with extensive investments in road rehabilitation. It was required to prepare the model for pavement existing conditions assessment for about 450 km motorway network and planning of pavement maintenance within the short period. By measuring surface deflections with HWD Dynatest, and by having at hand reliable data on pavement structure, thus the basis was formed for creating the mechanical pavement model. After the analysis of pavement surface deflections, idealized models of future condition were established, so-called “pavement condition matrix”. That matrix includes three classes of foundation condition and six classes of pavement condition. Each homogenous section of the analyzed motorway network may be represented by one of models in “pavement condition matrix”. Those models define efective modules of particular layers (for calculation overlay), residual bearing capacity of relevant pavement layers, and other information, significant for calculation. A basis was made that way for calculation of overlay structure. A significant percentage of asphalt layers and cement-treated aggregates layers possess residual bearing capacity. That is the reason to design maintenance strategies through a concept of preventive maintenance for pavement structure within design period of 20 years in service.
Roller-compacted Concrete Pavements in Norway 20 Years Experience
Roller-compacted concrete, as the name suggests, is concrete that in its unhardened state will support a roller while being compacted. During the period 1985 - 1995 a total of 68 km of concrete roads was constructed in Norway using this method, of which almost 60 km was in tunnels. The annual average daily traffic (AADT) on these stretches ranges from 200 to 10 000 vehicles per day, the majority having low traffic volumes. By 2005, almost 15 km of these concrete roads will have been paved over with asphalt. The remaining 53 km are located almost entirely in tunnels or on bridges. Experience indicates that: • compressive strength should be greater than C45 • thickness of concrete wearing surface should be greater than 150 mm plus rut depth • spacing between joints should not be greater than 6 - 8 m • the full width of the road should be cast in one operation to avoid bad longitudinal joints • only good quality aggregate with a max diameter of 22 mm should be used • dust has been a problem in some tunnels during the first few years of operation • quality of workmanship during casting has large implications for the final product • annual measurements show very small increases in rut depth • good maintenance and repair methods need to be further developed • the performance of the concrete wearing surface is so good in some tunnels that it should last 50-100 years without any major maintenance
Copyright (c) 2018 Jan Erik Dahlhaug, T. Haugødegård, Leif Jenssen, I. Markey, Karl Melby, P. Ø. Øhnstad,, O.L. Strømme, O. Sæveraas
The Study on Establishing the Pavement Performance Prediction by Artificial Neural Networks
Measuring the condition of current pavement is accomplished by collecting field distress data and synthesizing data to identify appropriate alternatives for rehabilitation or reconstruction. Many agencies have pavement management systems (PMS) to assist with data collection, evaluation, and decision-making during this process. The present serviceability index (PSI) is a common tool for quantifying information concerning the serviceability of the pavement. A primary factor used in establishing the PSI is the roughness of the surface profile. The PSI can also include standard distress criteria such as rutting, fatigue cracking, and thermal cracking. However, the actual causes and conditions of pavement distress are very complex. The statistical modeling can only consider no more than a few of the parameters, in a simplified manner, and in some cases various transformations of the original data. Because of the statistical nature of models this does not mean that cracking and rutting are not important, since they will react on the roughness of the surface profile. The artificial neural networks (ANNs) offer a number of advantages over the traditional statistical methods, caused by their generalization, massive parallelism and ability to offer real time solutions. In this paper, real pavement condition and the subjective present serviceability rating (PSR) in Taiwan are used to develop a generic intelligent pavement performance prediction using ANNs. In contrast to statistical analysis, it is concluded that the good predictive results can be obtained from the pavement performance model established by neural network.
NEW TECHNOLOGY OF SURFACE TREATMENT TARGETING TEMPERATURE REDUCTION OF ASPHALT PAVEMENT
Reducing asphalt pavement temperature during summer season contributes to mitigate rut generation of the pavement effectively. New surface treatment materials which reflects both sunshine and infrared rays has been developed and applied on existing asphalt pavement surface. The rate of solar reflectance of the pavement is from 30 to 50 % depending on the color of the materials (black to gray). Measured surface temperature of the pavement applied with this type of surface treatment is by utmost 20 degree K lower than that of conventional asphalt pavement. Its maximum temperature reaches 60℃ and more during summer in Japan. The effect of temperature of the pavement is verified by showing a smaller rut depth generation in accelerated actual wheel load test. Rate of rut depth is approximately one third compared to conventional pavement. This surface treatment applied for pedestrian pavement offers comfortable feeling while walking. This result also brings to alleviate heat-island phenomena in urban growth area, where the rate of pavement area in large as about 20%. This paper presents outline of newly developed pavement technology which reduces surface temperature due to prevent pavement from absorbing solar radiation and its reflection properties. This paper also shows measured pavement temperature of some colored types, durability of the asphalt pavement with and without application of this surface treatment.
Revised requirements for stiffness of ballast mats in new Norwegian railway lines
In the Oslo region new railway lines which include many and long tunnels below dwelling areas, now are constructed and planned. All the tunnel tracks are ballasted track. Ballast mats are the preferred remedial actions for reduction of ground borne noise. In the paper the work which lead to revised requirements for ballast mats are presented. Ballast mats having a stiffness of Cdyn,3 Hz = 0.01 N/mm3 have been installed in the most critical sections of the new tunnels. The required thickness of ballast for this track is 550 mm between sleeper underside and ballast mat surface. In the paper the definition and measurement method for maximum structure borne noise levels are given. The paper also shortly presents the results of a social survey on annoyance from this kind of noise, the calculation methods for structure borne noise transmission, and a method for measuring the vibration transmission from the tunnels before the track is installed.
Copyright (c) 2005 A. Brekke, H. Gåsemyr
Bearing capacity development on low volume roads (a 15-year case study)
This paper presents a 15-year study (1989-2004) of the actual bearing capacity development on a number of low volume road sections in Denmark. The project was started up in 1989 as part of the implementation of a PMS project and, apart from various deterioration technical aspects; the purpose was to study and uncover the actual bearing capacity development and to develop deterioration models for the bearing capacity of low volume roads in Denmark. The basis on which the mentioned test sections were selected will be mentioned in the paper as well as how they were divided into sections of 10x10 metres, how current and comprehensive analyses were made of materials and soil conditions. Furthermore, it will be discussed, how daily measurements and registrations were made of meteorological data, sounding of the groundwater level (which is high on some sections) and how an artificial lowering of the groundwater level influenced both negatively and positively on the road deterioration. Finally, results will be presented from selected sections where the bearing capacity has developed as expected, but in some cases also in a rather surprising way. KEY WORDS: bearing capacity, PMS (Pavement Management System), FWD (Falling Weight deflectometer), design, deterioration, distress, models, groundwater, condition; GPR (Ground Penetration Radar), RoSy (RoSy Road Systems), residual life (based on Danish design criteria).
Residual life (based on Danish design criteria)
IMPROVEMENT OF BALLASTED TRACKS USING SLEEPER PADS
Despite the long history of conventional, ballasted railway superstructures further development is needed. The requirements like convenient deformation behaviour (settlements), low-priced maintenance and low noise emissions (air-born and structure born) have been boosted continuously especially for high speed applications. The track-settlement behaviour is influenced by the service conditions and the ballast pressure within the contact area between sleeper and ballast. The contact pressure can be reduced by increasing the contact area or by adding additional resilient components within the superstructure to activate greater load distribution by the rails. Qualified sleeper pads (USP under sleeper pads) give possible solutions. Measurements at field tests in Germany show a better track settlement behaviour. Furthermore additional resilient elements like sleeper pads have great influence on the dynamic vibration behaviour. The vibration velocities have been measured by special ballast stones equipped with accelerometers. Results concerning tracks with additional sleeper pads are available up to 160 km/h and have been compared with measurements performed on tracks with resilient rail pads. Requirements for sleeper pads are resistance against pressure peaks by ballast stones, durable resilient properties, sufficient vibration behaviour and applicability for conventional construction and maintenance procedures. The experiences born by laboratory tests and by test sections in revenue lines have been accounted for the new composed technical delivery conditions of the German Railways DB-AG for sleepers equipped with sleeper pads.
Analysis of Seasonal Bearing Capacity Correlated to Pavement Deterioration in Cold Region
The Laboratoire Central des Ponts et Chaussées (France) and the Ministère des Transports du Québec (Canada) have developed a joint research project on the behaviour of pavements in a cold region. This project aims to increase understanding about fatigue damage of pavements under the combined effect of traffic and a decrease in bearing capacity during the thawing period. An experimental site was constructed in Quebec in 1998 and its behaviour was monitored for six years. Pavements with a cement-treated base and a hot-mix asphalt base were selected. Two test beds of each type were constructed. One of these two test beds was thermally insulated by a layer of extruded polystyrene, while the second was not, so that the researchers could distinguish between traffic and climate effects. This paper presents the analysis of the seasonal variation of bearing capacity related to deflection, subgrade modulus and tensile strain. Also, an analysis of the results describes the difference observed between the quasi-static and dynamic responses and the relationships between traffic loading and pavement performance.
Copyright (c) 2005 Y. Savard, K. De Blois, M. Boutonnet, Pierre Hornych, C. Mauduit
Full-Scale Testing of Pavement Response by Use of Different Types of Strain Gauges
From 2002 to 2004 the COST action 347 (European Co-operation in the field of Scientific and Technical Research) was organized under the title “Improvements in Pavement Research with Accelerated Load Testing”, including full-scale pavement tests at a number of European research laboratories. In Lausanne, Switzerland (EPFL) a test pavement of a fullyflexible type was constructed and equipped with strain gauges of different types usually in service in Europe. The loading-facility in Lausanne is an indoor test-pit where road structures can be repeatedly loaded by a linear heavy-pavement-rutting-tester. Within the ALT-program the loading conditions were controlled, comprising a variation of the pavement temperature, a variation of the loading parameters (axle load, tire type and tire pressure, loading speed) and an investigation of the lateral distribution of the responding strains with respect to the load axis. Longitudinal and transversal signals were recorded, that resulted from measurements on the different types of strain gauges and in two different depths: 40 mm and 220 mm from the pavement surface. As a result the shape and the order of magnitude of strains were found for different levels of observation and for defined loading conditions. This makes it possible to comparatively analyse the functionality of the different types of strain gauges on the one hand, and, on the other hand, to derive important information on pavement response that may be used in pavement modelling and performance prediction.
Copyright (c) 2005 P. Chenevière, M. Wistuba, A.-G. Dumont