1,721,095 research outputs found
Use of local materials for road construction - Innovative stabilization techniques for crushed rocks
No full textThe Norwegian Public Roads Administration is currently running the “Ferry-free coastal route E39” project, which reduces the travel time along the Norwegian highway E39 connecting Trondheim to Kristiansand. The plan includes the creation of several long tunnels, which will generate a surplus of blasted rocks; these unbound granular materials are often damaged from the intensive blasting and will in many cases fail the strict criteria stated in the pavement design guidelines. However, they could be used in the road unbound layers close to the place of production, entailing a sustainable cost-benefit application.
The geology encountered along the E39 road alignment is mapped: several rock types (igneous, sedimentary and metamorphic) are spread in the locations of the tunnelling operations. The existing code defines requirements for road unbound layers in terms of Los Angeles (LA) and micro-Deval (MDE) tests. The major part of the rocks has igneous origin and fulfils the standard check procedures (“strong” rocks); anyway, a considerable quantity of the rocks having different origin does not (“weak” rocks). The materials collected and used for the research mission are characterized by means of thin-section microscopy, X-Ray Diffractometry (XRD), X-Ray Fluorescence (XRF) and Scanning Electron Microscope (SEM). Moreover, the crushability of some different rock types connected to the road construction phase and service life phase is analysed.
The research investigates how to promote the use of the “weak” rocks using some possible techniques in the laboratory. The first approach is the mixture between the various types of rocks available in situ. The second approach is additive application; two different non-traditional additive types are examined: one is polymer-based, the other one is lignin-based. Repeated Triaxial Load Tests (RTLT) are used to assess the additives’ effectiveness. The results are interpreted according to some models available in literature and a finite element model is developed to simulate the repeated triaxial load test and compare its results.
Finally, the research investigates the performance of the additives in the field. Three typical base layer sections are built and added with water (no treatment), water and polymer-based additive, water and lignin-based additive, respectively. The development of the layers’ stiffness and deformation properties are mainly assessed by means of Light Weight Deflectometer (LWD). Dynamic Cone Penetrometer (DCP) and rutting formation evaluation also contribute to investigate the field performance.
The results of laboratory and field test campaigns indicate that both the polymer-based and lignin-based products can enhance the mechanical properties of the “weak” crushed rocks
Properties of coarse unbound granular material used in road construction
No full textRoad pavements are designed to ensure safe, accessible roads according to the expected traffic volume and composition and climate conditions. These parameters are considered in overall evaluations balancing the effects on monetary costs, traffic safety, health and work environment, external environment, climate, traffic management preparedness and more. The introduction of a mechanisticempirical (ME) pavement design system with performance prediction tools facilitates improved project specific analysis of deterioration mechanisms based on material, traffic and climate data. Hence, the pavement design may be optimized based on a defined balance between the predicted pavement performance and costs. To utilize the potential of such tools, comprehensive characterization of materials and other input data is a prerequisite.
Coarse crushed rock (CR) materials with maximum particle size ranging from 125 mm to 250 mm are commonly used in structural layers in Norwegian road construction. Such gradings are uncommon outside of Scandinavia, and the existing literature is limited. Hence, there is a need to characterize the properties of coarse unbound granular materials used in road construction.
Stiffness of materials is one of the main parameters in pavement analysis. Laboratory investigation to characterize the stiffness of pavement materials is commonly conducted with the repeated load triaxial test. However, characterization of standardized Norwegian subbase materials would require sample sizes of up to 1250 mm in diameter and 2500 mm in height. Hence, this study investigates stiffness characterization with repeated load triaxial testing on downscaled materials combined with in-situ fullscale characterization using the plate loading test.
The laboratory investigation with large-scale repeated load triaxial test was conducted with 300 x 600 mm samples of downscaled open-graded and dense-graded materials. The upper sieve size of the downscaled materials was 22–63 mm, and the results indicated that downscaling of open-graded materials could be applicable for characterization of stiffness. However, the results for dense-graded materials indicated reduced stiffness with decreased upper sieves size.
The in-situ field test was conducted with three parallel sections with different subbase materials: Section 1 with open-graded CR 22/125 mm (layer thickness 600 mm); Section 2 with dense-graded CR 0/125 mm (layer thickness 600 mm); Section 3 comprising dense-graded CR 0/32 mm as interlocking layer (layer thickness 100 mm) on open-graded CR 22/125 mm (layer thickness 500 mm).
Sections 1 and 2 were designed to compare open-graded and dense-graded subbase materials with the same upper sieve size. Two weeks after construction, the stiffness of the dense-graded subbase was 15% higher as compared to the open-graded subbase, measured with the plate loading test utilizing a 300- mm plate. The dense-graded subbase exhibited a significant increase in stiffness by 14% after one year with no further compaction or traffic loading. Consequently, the stiffness for the dense-graded CR 0/125 mm was 36% higher as compared to the open-graded CR 22/125 mm after one year.
Sections 1 and 3 were designed to compare the influence of the interlocking layer. In Section 1, CR 22/125 mm was compacted at a 600 mm thickness and CR 0/32 mm was applied in a 0–50 mm depth to obtain an interlocked surface for the coarse open-graded subbase. Section 3 was designed with a 100 mm layer of CR 0/32 mm which could be considered a separate upper subbase layer. Based on the plate loading test using a 300-mm plate, the stiffness measured in Section 3 was 19% higher as compared to Section 1 after two weeks. After one year, with no further compaction or traffic loading, the difference increased to 36%.
The plate loading tests with 300-mm plate were combined with earth pressure cell measurements directly below the test plate. Measurements were conducted at a 600 mm depth, which was the interface between the subbase and subgrade. The plate loading test is conducted in two cycles, and measurements during the six loading steps of the second cycle were compared for Section 1 and Section 2. The stress level measured in Section 1 was on average 55% higher for all loading steps as compared to Section 2.
The ratio of (change in measured stress at 600 mm depth)/(change in applied stress at the surface) was computed for consecutive loading steps. The average ratio was 12.4% in Section 1 and 9.7% in Section 2, indicating a better load distribution for the dense-graded CR 0/125 mm as compared to the opengraded CR 22/125 mm.
Sections 1 and 2 were analyzed by use of Boussinesq’s linear elastic theory and the KENPAVE ME design and analysis software. The applied loads were equal to the load and circular area of the plate loading test. The average vertical stress at 600 mm depth for all loading levels based on Boussinesq’s theory was 52% and 72% as compared to the stress measured with earth pressure cells in Section 1 and Section 2, respectively. Computations of vertical stress by KENPAVE were on average 36% and 51% for all loading levels as compared to the in-situ measurements in Section 1 and Section 2, respectively. Hence, both methods estimated a lower vertical stress below the 600 mm thick subbase, as compared to the in-situ measurements with earth pressure cells.
The in-situ plate loading test results and earth pressure cell measurements indicate a higher stiffness and better load distribution properties for the dense-graded subbase as compared to the open-graded subbase. However, the results are limited to one rock type and one subgrade type measured with the plate loading test, and further research should be conducted with complementary rock types, gradings, and subgrades.
To exemplify estimates of emissions related to unbound granular materials in pavements, a case study was conducted on frost protection of roads. Frost design according to the current design regulations and frost quantities based on the period 1981–2010 were compared to frost design based on projections for 2071–2100. The Intergovernmental Panel for Climate Change publishes Representative Concentration Pathways, which are future scenarios for climate change based on population size, economic activity, lifestyle, technology, energy usage, land use patterns, and climate policy. Two scenarios were employed in the study, with RCP8.5 reflecting “business as usual” and RCP4.5 representing an intermediate scenario between RCP8.5 and RCP2.6, which is the 2°C goal. In combination with the RCPs, three alternatives were computed: Alternative 1 with fossil fuel; Alternative 2 with electric machinery and biofueled trucks; Alternative 3 with transition from fossil fuel to all-electric machinery. The emission models were based on LCA tools VegLCA and Stein LCA.
E6 Kolomoen–Moelv (E6 K–M) which is a 40 km four lane highway in inland Norway, and E18 Tvedestrand–Arendal (E18 T–A) which is a 22 km four lane highway on the Norwegian southern coastline were selected for the case study. The estimates with frost quantities for the period 1981–2010 and Alternative 1 with fossil fuel were 29,017 and 6,298 tonne CO2-equivalents for E6 K–M and E18 T–A, respectively. For Alternative 1, E6 K–M reductions were estimated at 31% and 46% under RCP4.5 and RCP8.5, respectively. E18 T–A reductions with Alternative 1 were estimated at 47% and 65% under RCP4.5 and RCP8.5, respectively. For Alternative 3, the estimated reductions under RCP4.5 and RCP8.5 were 71–78% and 77–85%, respectively.
The 130 mm difference in pavement depth for E18 T–A under RCP 4.5 as compared to RCP8.5 was estimated at 50 kg CO2-equivalents per meter road for Alternative 1. Thus, if the implementation of ME design reduces material usage or increases the expected service life for most of the future public road projects, it could lead to considerable accumulated reductions in emissions related to pavement materials
Laboratory investigation of frost susceptibility of crushed rock aggregates and field assessment of frost heave and frost depth
Full text linkIn Nordic countries that experience seasonal frost, understanding how it affects the service life of linear transport infrastructures such as roads and railways is essential. Frost action both regroup frost heave and thaw weakening processes. This research focuses on frost heave, which occurs when three conditions are met: freezing temperature, water availability and frost-susceptible materials. Frost susceptibility is therefore defined as the ability of an unbound granular material (natural soil or crushed rock aggregate) to form ice lenses due to cryosuction, which is the suction of water to the frost front. Frost heave in a frostsusceptible material lifts the layers above the freezing front. Many kinds of damage are attributable to frost heave, such as cracks in and unevenness of the road surface, making it uncomfortable and even dangerous for road users. Frost heave and subsequent thawing can significantly reduce the service life of roads and are accompanied by high associated maintenance and reparation costs. Knowledge of the frost susceptibility of the materials comprising the different layers of transport infrastructure is therefore crucial to optimal frost design.
This research mainly aimed to characterize the frost susceptibility of crushed rock aggregates. Laboratory experiments using a multi-ring frost cell were carried out to estimate the segregation potential of the 0-4 mm fraction of crushed rock aggregates. Twenty-four tests performed on nine different rock types found that crushed rock aggregates with a fines content of <63 μm between 11.6% to 25.5% are highly frost susceptible. The study found poor correlation between <63 μm fines content and segregation potential. The latter was used to characterize the frost susceptibility of the different crushed rock aggregates primarily for its capacity to estimate frost heave magnitude easily. The use of a grain size criterion, as presently used in Norway, seems to be efficient for dividing non-frost-susceptible from frost-susceptible aggregates, but does not allow estimation of crushed rock aggregates’ segregation potential with a good degree of confidence.
As frost heave tests require a costly laboratory setup and specialist personnel, the segregation potentials of crushed rock materials were estimated using material index properties such as initial water content, liquid limit, mean particle size of the fine fraction and specific surface area of the fine fraction. This method is used by the Quebec Ministry of Transportation for soils, and the goal here was to assess the suitability of the methodology for use with crushed rock aggregates. It was found that estimation from material indexes gave segregation potential results within a range of ±15% compared to those obtained from frost heave tests. There was a direct correlation between the specific surface area of the fine fraction of a crushed rock aggregate and its segregation potential, from which an equation was developed. The study showed that the crushing phase had an effect on the frost susceptibility of the tested crushed rocks. Aggregates are more frost susceptible after the first crushing stage than after the third or fourth crushing stages. The hypothesis that the fine fraction is enriched by weak minerals at the first crushing could explain this behaviour, but further research is necessary before this theory can be presented with confidence.
The design was optimized by modelling three road sections with different frost protection layers using the SSR model and the I3C ME software. The fully-instrumented test site is situated in the Røros municipality where harsh winters are the norm, with the freezing index of an average winter equal to that of regions such as Oslo, Trondheim, Narvik, Tromsø etc. It was found that the SSR model is suitable for both frost penetration and frost heave estimation for thick (2.05 meters) layered road structures. The SSR also permitted the back-calculation of key parameters such as dry density, moisture content and segregation potential, making it useful for assessing existing infrastructure parameters. Using a segregation potential function, i.e. segregation potential according to time, was found to produce optimal frost heave estimations in a transient thermal regime
Influence of Subsoil Conditionson the Design and Performance of Flexible Pavements
Full text linkThe effect of subsoil conditions is one of the prominent factors that control both the design and performance of flexible pavement structures. Despite having a wide range of empirical methods from measurements and experience, the quantification of the short-term and long-term physical processes of geo-materials in roads is not yet fully understood. Particularly, subgrade soils have not got the required attention in the characterization of pavement materials although they are known as the “foundation” of the pavement structure. This conception has raised — partly due to the notion that the stress from the traffic is low at the subgrade level — and partly, due to existence of a wide variety of soils, in contrast to standardized materials for asphalt, base, and sub-base layers. Lowtraffic volume roads, however, have often thin asphalt layer, and the stress magnitude from the traffic loads can be significant at the subgrade level. In addition, subgrade soils are most susceptible to the variation of local and environmental conditions.
With the fact that the subgrade layer is an integral part of pavement analysis, this thesis aimed to address the main important issues of characterization of subgrade soils in mechanistic pavement design methods. The objectives of this research have been classified within three main themes: (1) to propose numerical models to characterise subgrade soils for practical mechanistic-empirical pavement design method, (2) to enhance the quantitative characterisation of subgrade soils — instead of the widely used qualitative characterizations in practice, (3) to use finite element method to optimise road design and maintenance practices.
The main contributions of this study are: First, an overview of research literature is provided on the existing methods and knowledge of characterization of subgrade soils in flexible pavement design. The geotechnical aspects in pavement design are outlined to identify the research needs and to formulate the main research questions. Second, a method for formulation and implementation of a nonlinear resilient modulus model is presented. The method in this study has been found to be more versatile than the existing methods for characterization of subgrade soils since it considers the effects of both confining pressure and deviator stress. The implications of this method were found to be important aspects of pavement design for low-traffic volume roads.
Third, a constitutive model is proposed to predict the long-term deformation of subgrade soils. The model is formulated based on the plastic strain from first loading cycle, and an additional parameter that accounts for the proximity of the applied stress to the static strength of the soil. The predicted results from the proposed model showed a good agreement with laboratory tests for deviator stress level up to 50% of the static strength of the soil. Fourth, based on finite element modelling of soil compaction, the lift thickness of fine-grained soils has been observed to be defined as a function of cohesion and friction angle. This study suggested the optimisation technique of lift thickness depending on the strength parameters of soils to improve the rolling strategy of soil compaction during road construction.
Finally, a finite element modelling technique is presented for prediction of spring thawing in frozen subgrade soils. Since there are no well-established methods for modelling of the thawing process, analytical solutions are used to validate the numerical methods for simplified boundary conditions. Further, the application of finite element method is extended to model multi-layer pavement structures with the thermal and physical properties of each layer and varying surface temperature. In this study, the thaw depth is observed to be linearly proportional to time for sinusoidal surface temperature variation — in contrast to the existing knowledge of thaw rate for homogeneous frozen layers where the thaw depth is proportional to the square root of time.PhD i bygg, anlegg og transportPhD in Civil and Transport Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
How wear affects road surface texture and its impact on tire/road noise
Full text linkMechanical pavement wear in the Nordic countries is essentially influenced by the use of studded tires during long winter seasons. The abrasive effect of the studded tires is the cause of significant damage on the pavement and a contributor to rutting. In addition, the mechanical aggregate removal due to the studded tires is the reason for significant changes in the road surface texture. At traditional dense asphalt pavements, the mechanical wear is initiated by the abrasion of the mortar, which leads to a protrusion of coarse aggregates. Regarding the noise characteristics of asphalt pavements, those texture alterations will have a negative impact.
Several methods to reduce the noise emission have been investigated. However, in the Nordic countries, the reduction of maximum aggregate size in the mix design of asphalt pavements is considered the most efficient way to develop satisfactory pavement noise characteristics. The challenge is to find the right balance between the wear of the mortar and the wear of the coarse aggregates to produce a limited worn surface with positive acoustical characteristics.
Within this study, common Norwegian asphalt mixture types, including different rock materials and binder types were investigated to study the effect on pavement wear, the resulting changes in surface texture and the road's noise properties. Laboratory tests were carried out to simulate the wear by studded tires. The texture characteristics were measured on the test specimens, both initially, during and after testing. In addition, pavement wear, surface texture and tire/road noise was measured on several full-scale test sections.
A reduction of the maximum aggregate size causes an increase in mechanical wear by studded tires. However, by reducing the maximum aggregate size, both the initial surface texture and the surface texture of the worn pavement have a positive effect on the acoustical characteristics of the asphalt pavement. The characteristics of the rock material used for the aggregates in the asphalt mixture is crucial for the pavement service life and the development of the surface texture. By using a rock material in the fine fraction that is more resistant against the wear by studded tires than the rock material used for the aggregates in the course fraction, the wear of the pavement surface will be balanced and result in a surface texture that is favorable for little noise generation. To reduce the wear and keep positive acoustical characteristics, a gap graded asphalt mixture type is preferable
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Undersøke presisjon og effektivitet av Ground Penetrating Radar for å definere hulrom i asfaltdekket
No full textGround Penetrating Radar, GPR, blir benyttet til kvalitetskontroll av hulrom i asfaltdekker, både i Sverige og Finland. Det er her blitt akseptert som en relativt god måte å vise variasjonene i hulrom i dekkets lengderetning. På bakgrunn av dette har det blitt gjennomført sammenligningsmålinger av hulrommet i to reasfalterte strekninger i Akershus fylke. En måling utført av isotop densitetsmåler (Seaman C300) sett opp mot et kalibrert GPR-målt hulrom.
Resultatene viser små variasjoner i målinger gjort med Seaman C300. 70 % av målingene på Fv. 229 er innenfor akseptabel feilmargin, sammenlignet med resultatet fra GPR-målt hulrom.
Oppgaven undersøker rådata fra tidligere gjennomførte målinger med GPR, og resultatet sammenlignes med målinger gjort med isotop densitetsmåler. Oppgaven inneholder en teoridel som beskriver tradisjonelle metoder å undersøke hulrom, deretter en beskrivelse av hvordan GPR fungerer, og kort om GPR og hulromsundersøkelser. Presentasjon av data er illustrert av figurer og tabeller under kapittelet resultater. Deretter blir tolkningen diskutert og på grunnlag av dette lyder konklusjonen:
- GPR målt hulrom kan potensielt brukes som et supplement til kontroll av kvalitet i asfalterte dekker.
- Det å analysere data fra GPR har mye å si for nøyaktigheten av resultatet, derfor er det nødvendig med gode erfaringer av slike analyser.
- GPR er lett anvendelig og det går hurtig å hente inn data. Derfor er det et brukbart verktøy å supplere med når en skal undersøke hulromsandelen i asfaltdekker
- …
