Standard Axle Research Articles

Ultra Thin Continuously Reinforced Concrete Pavement Development in South Africa

Ultra thin continuously reinforced concrete pavements (UTCRCP), in literature also referred to as Ultra Thin Heavy Reinforced High Performance Concrete (UTHRHPC), have been used in Europe successfully as a rehabilitation measure on steel bridge decks and reported on at the 5th International CROW workshop in Istanbul (2004). This concept has been explored further in South Africa for use as a road strengthening measure by constructing experimental sections of 50 mm UTCRCP directly on top of both natural gravel and cement-treated natural materials. During the experiment the composition of the UTCRCP layer was varied in terms of mix design, steel fibre type and content, reinforcing steel mesh diameter and spacing. To date a total of 10 experimental sections have been tested using the Heavy Vehicle Simulator (HVS) and rendered structural lives that varied from 5 million to 90 million equivalent standard (80 kN) axles on medium to weak support structure. The results obtained were then evaluated through 3D-finite element modelling and the design was refined using laboratory tests. The refined UTCRCP design was then subjected to further HVS testing. The paper discusses the above process in more detail.

Computational and experimental studies of vibration-protective properties of a pneumatic wheel of the MTZ-82 BELARUS tractor with external spring-hydraulic mini-suspension

BACKGROUND: Currently used in various sectors of the national economy, numerous wheeled suspensionless vehicles on pneumatic tires have a low level of vibration protection of the frame and limited cross-country ability. Therefore, the development and study of the design characteristics of a pneumatic wheel with increased elastic-damping properties and cross-country ability is a relevant technical problem. AIM: Development of the design and study the vibration-protective properties of a pneumatic wheel with an external spring-hydraulic mini-suspension to improve the ride smoothness and cross-country ability of large-sized suspensionless vehicles. METHODS: A description of the design of a wheel with mini-suspension and a support roller is presented. The wheel modeling was carried out in the PascalABC software, which takes into account the nonlinearity of the total force of the pneumatic tire and the spring-hydraulic mini-suspension, which is installed parallel to the tire at an angle to the vertical axis of the wheel. The test method consisted of comparison of free and forced vibrations of the rear pneumatic wheel of the MTZ-82 BELARUS tractor with a 400-965/15.5-38 tire, which operated without and with mini-suspension at a vertical load of 0.6 tons and various excessive pressure in the tire. RESULTS: The results of computational and experimental studies show that if the tire is radially compressed by 75 mm, the excess pressure inside the pneumatic wheel almost does not change, and if the pressure in the tire decreases from 1.6 to 0.4 bar, the resonant vibration frequency of the standard wheel axle decreases by 25%, while the dynamic coefficient remains unacceptably high (more than 5), leading to the tire breakaway from the supporting surface. Installing a mini-suspension parallel to the wheel in the form of a spring-hydraulic shock-absorbing strut leads to an increase in the resonant frequency by 1 Hz, however, the resonant peaks are reduced by almost 3 times to a dynamic coefficient of 2.5...2, which significantly increases the ride smoothness of suspensionless vehicles and reduces the likelihood of wheel breakaway from the supporting surface. CONCLUSION: It was found with the studies that the proposed wheel with a mini-suspension as a spring-hydraulic strut and a support roller has a relatively simple design, ensures high vibration-protective properties with small amplitudes of kinematic disturbance and can be used to improve the ride smoothness and cross-country ability of wheeled suspensionless vehicles.

On the Influencing Factors of Non-asphalt Originated Rutting in Flexible Pavements

Rutting can substantially impact pavement serviceability and driving safety. Since most of the permanent deformation develops in the unbound layers beneath the asphalt course, the focus should be on these layers. In this research, rut depths were calculated and analyzed using the high-cycle accumulation model, where the resilient response and cyclic strain amplitude were determined through finite element analysis. Consequently, settlement depression curves were described for various subgrades and cross-sections. It was observed that grain size distribution, particularly the uniformity coefficient, plays a decisive role in rutting depth. Analysis of the relationship between settlements and axle loads indicates that the calculated settlements demonstrate a linear increase relative to the axle load. For various axle loads, the number of axle passes required to induce an equivalent settlement to the standard axle was established. The possibility to reduce the depth of ruts by increasing the thickness of the subbase was also investigated. It was found that the predicted rutting is highly influenced by the particle shape (angular, rounded, or mixed material) of the subbase. It was found that the primary portion of permanent deformations occurs within the subgrade.

Fatigue Damage in Asphalt Pavement Based on Axle Load Spectrum and Seasonal Temperature

In asphalt pavement structure design, traffic axle loads and pavement layer temperatures are crucial factors affecting fatigue damage calculations. To investigate the differences in fatigue damage calculations caused by different characterizations of traffic axle loads and temperature, fatigue damage calculations were conducted under equivalent standard axle loads (ESALs), axle load spectra (ALS), constant temperatures, and seasonal temperature variations using the field data from an expressway in Shandong Province, China under seven calculation plans. The results indicated: (1) the annual traffic composition is dominated by vehicle Type 9, with a proportion of about 43% in all the vehicle types, and its load level is also high, with a proportion about of 80% in the heavy load interval at all axle types; (2) The ESALs method underestimates the actual fatigue damage incurred in asphalt pavement by 6.04 times, with an accumulated damage of 2.34 × 10−9 (ESALs), 1.69 × 10−8 (ALS), respectively; (3) The fatigue damage results from a single month with consistent temperature showed similar trends, with an accumulated damage of 1.50 × 10−5, 9.07 × 10−5, respectively; (4) The cumulative fatigue damage calculated using the ALS method across the four seasons, respectively, is 6.51, 5.88, 6.42, and 4.60 times that of the fatigue damage calculated using the ESALs method. Although the ratio of fatigue damage between the two characterizations of traffic axle loads remains consistent, which is 6.04, the fatigue damage calculation that accounts for temperature variations can reveal seasonal trends in fatigue damage development. Based on the axle load spectra and considering temperature variations, fatigue damage calculation will be more closely related to the actual service state of asphalt pavement. These research findings provide insights for estimating asphalt pavement fatigue damage to some extent.

Utilization of alkali-treated areca fibers for stabilizing silty sand soil for use in pavement subgrades: Analysis using IITPAVE software

The increasing growth of urban areas and the rise in infrastructure development activities have put a strain on the availability of land with desirable soil conditions. This has led to the development of several stabilization techniques that can be used to improve the properties of weaker soils for construction. The research presented here explores the impact of inducing randomly oriented alkali-treated areca fibers for stabilization of silty sand soil. A sequence of experiments was carried out on the soil-fiber mixtures to investigate the strength of the soil after stabilization. At increments of 0.2%, the fiber dose varied between 0 – 0.8% of the dry weight of the soil. The tests conducted includes compaction tests, California bearing ratio (CBR), unconfined compression strength (UCS) tests, and unconsolidated undrained (UU) triaxial tests. The results obtained showed a notable increase in the strength of the soil-fiber mixtures. An increase in fiber content was found to increase the OMC (optimum moisture content) values and decrease the MDD (maximum dry unit weight) values. The maximum strength of the soil-fiber mixture was obtained at 0.6% fiber content. This makes it possible to use silty sand soil subgrades for low-volume roads with a traffic of less than 2 million standard axles based on the IITPAVE analysis. In essence, the test findings indicated that the ideal fiber content to be 0.6%. Stabilization of local on-site soils is one of the sustainable practices that can help extend the life of a pavement and lessen the need for more frequent repairs/maintenance.

A reliability-based mechanical-empirical design method for flexible pavements containing cement-treated magnesite mine tailings as subgrade

The large-scale mining of magnesite generates substantial quantities of magnesite mine tailings (MMT), which pose a significant threat to soil, water, and air quality. Utilising cement-treated MMT as a subgrade material presents a promising solution to address this environmental challenge. However, the existing mechanical-empirical design methods cannot be directly employed due to the uncertainties associated with the various design parameters particularly the behaviour of cemented MMT. This research introduces a novel reliability-based MEM design method to design flexible pavements incorporating cemented MMT as subgrade. A three-layered flexible pavement configuration, with a middle granular layer sandwiched between the top bituminous layer and the bottom stabilised subgrade, was examined. The response surface model and finite element model were developed to determine the fatigue and rutting strains of the pavement. Monte Carlo simulation was adopted to compute reliability. Further, a sensitivity analysis was performed to probe the contribution of input parameters on the reliability of pavement. The developed methodology was illustrated with a case study. Reliability analysis revealed that the cemented MMT pavement achieved reliabilities of 97.44% and 96.27% for fatigue and rutting criteria, respectively, under a design traffic load of 30 million standard axles (msa). Additionally, the sensitivity analysis identified the modulus of elasticity of the granular layer and bituminous layer as the most critical input variables. Thus, the developed design methodology for pavements incorporating MMT enables the engineers to design MMT-based flexible pavements considering the uncertainties.

Testing the Feasibility of Selected, Commercially Available Wearable Devices in Detecting Agricultural-Related Incidents

HighlightsThe purpose of this research was to validate a test procedure for using commercially available smart technologies in detecting an agricultural-related incident.A convenient selection of commercially available wearable devices was used to measure the inertial qualities of simulated incidents.Simulated ejections, falls, and upsets were performed to recreate leading causes of agricultural injuries and fatalities using an anthropomorphic test device.Only 2 of 27 simulated incidents triggered detection on the selected wearable devices tested.The results of this study were inconclusive in determining the feasibility of commercially available wearable devices in detecting agricultural-related incidents. More research is needed to develop an improved testing procedure.Additional collaboration is needed with manufacturers of wearable incident detection devices to clearly identify potential applications and limitations of their devices.Abstract. A study was conducted to test a selection of commercially available wearable devices to determine their feasibility for triggering incident detection during a variety of simulated agricultural incidents with high risk of causing injury. The goal was to ultimately increase survivability outcomes for victims by enhancing notification and reducing response time from emergency services. A 50th percentile adult male anthropomorphic test device (ATD). was fitted with a convenient selection of commercially available wearable smart technologies to measure the responsiveness of the technology’s incident detection software. Devices used for this testing were: (1) Garmin Vivoactive 4 smartwatch; (2) Apple Watch Series 7 (Bluetooth only and cellular models); and (3) Movesense Active tracking device. A Samsung Galaxy S22 smartphone and an Apple iPhone 12 smartphone were used to connect the wearable devices and measured impact through their internal inertial measurement unit (IMU) sensors. Simulated ejections from equipment, vertical falls, and vehicle overturns were performed with the ATD. Side upsets were simulated with the ATD positioned in the operator station of a 52-drawbar horsepower (dbp), two-wheel drive, standard front axle, diesel tractor, weighing 6500 pounds. The tractor was equipped with an approved ROPS. Side upsets were also simulated using a 22-horsepower zero-turn mower, with the ATD positioned in the operator seat. Falls were simulated from heights of up to 4.57 meters. After each simulated incident, devices were examined to determine whether or not incident detection was successfully triggered. Data was then collected from an internal sensor logging application installed on the selected devices. It was found that the incident detection feature on the identified wearable devices only triggered in specific scenarios. Only 2 of the 27 simulated incidents successfully triggered incident detection on one device. Only the Garmin Vivoactive 4 smartwatch triggered incident detection. No device was triggered during the ATD impact in simulated tractor upset testing or in simulated zero-turn mower upset testing. It was concluded that these devices, in their current form, are not reliable for use in detecting serious agricultural-related injuries, especially considering the lack of adequate cell phone coverage in the areas in which these incidents are most likely to occur. Keywords: Agricultural incident simulation, ATD, G-force, Incident detection, Sensor fusion, Smart watch.

Mechanical properties of cold mixed asphalt

The mechanical and performance characteristics of cold mix asphalt derived from straight-run bitumen blended with dissolved polythene were assessed to determine the engineering, environmental, and economic feasibility of a recently developed product for pavement maintenance. The cold mix asphalt binder was created by treating a portion of straight-run bitumen with chemically dissolved polythene waste sachets at a temperature of approximately 80°C, employing an alkaline emulsifier, chemical surfactant, and water. The formulation for the cold mix asphalt involved 35% coarse aggregates, 65% fine aggregate, and 10% mineral filler, with an optimal binder content of 8.3%. Standard laboratory Marshall tests, static loading/unloading in both laboratory and field settings, and real-time traffic loads were applied to the cold asphalt mixes to establish comparative performance. The Marshall Stability, flow, and density of the experimental cold mix asphalt were determined as 5.08 kN, 4.0 mm, and 1.98 g/cm3, respectively. In comparison, the corresponding values for the other three commercially available cold asphalt mixes ranged from 0 to 4.27 kN, 0 to 5.5 mm, and 1.60 to 1.85 g/cm3. The rate of deformation of experimental cold mix with respect to time and traffic load respectively 0.0086mm/week and 0.00877mm/standard 80 kN standard axle, which are more favorable than the corresponding values for the commercial mixes.

Cement Stabilization of soft soil subgrade and Cost Analysis

The soft soil when present in subgrade creates a lot of problem in highways. Due to soft soil subgrade, the rutting is predominant cause of flexible pavement failure all around the world. This kind of soil is either replaced or modified prior to construction of other layers of road to minimize the formation of rut. This study deals with stabilization of soft soil subgrade by cement. The sample was collected from a depth around existing road subgrade. A series of laboratory tests on untreated soil sample was first done to determine the competency of soil as a subgrade layer followed by preparation of sample with varying stabilizer content i.e. 4%, 6% and 8% cement by weight of dry soil, to determine the optimum stabilizer content. Samples with varying cement content were also prepared for California Bearing Ratio (hereafter, CBR) and Unconfined Compressive Strength (hereafter, UCS)with different curing periods i.e. 7 days for CBR and 3, 7, 14 and 28 days for UCS. UCS test on these sample showed a significant improvement over the values of natural soil without stabilizer. CBR showed a similar trend and the resulting modified soil was competent enough to be used as a subgrade for heavy traffic condition. The pavement was modelled using Kenpave for 30 and 50 million standard axle (msa) traffic intensity to determine the ideal pavement section for two types of pavement used in this study. In addition, the cost of construction for replacement method and for cement stabilization are determined using norms of Department of Road and District rate of Kathmandu and are compared. The cement stabilized soil with optimum content is found to be cheaper than conventional method of replacement.

Exploring potential of Marshall-RT as simple performance test to evaluate rutting resistance of asphalt mixtures

ABSTRACT This study explored a new simple monotonic Marshall rutting test (Marshall-RT) to evaluate the rutting resistance of asphalt mixtures. The Marshall-RT test setup combines the Marshall fixture (at the bottom) and the IDT fixture (at the top). The rutting resistance of asphalt mixtures was evaluated using peak load (Pmax) and work done for the deformation damage obtained from the load-displacement curve. Nine plant-produced asphalt mixtures having different types of binders (unmodified, crumb rubber modified binder (CRMB)), and polymer modified binder (PMB)) and gradations having different nominal maximum aggregate sizes (NMAS) were evaluated. The Marshall-RT test parameters (i.e. Pmax and W P m a x ) have shown a strong correlation with fundamental (i.e. Flow Number (FN)), simulative (i.e. Hamburg wheel tracking test (HWTT)), and simple monotonic (i.e. Ideal rutting test (IDEAL-RT)) rutting tests. Moreover, the Marshall-RT test has shown good repeatability, the highest differentiation potential, and consistent ranking with other rutting tests. Furthermore, for high traffic levels (i.e. 100 MSA (Million Standard Axle)), at 50°C preliminary minimum threshold criteria were proposed for Marshall-RT (Pmax and W P m a x ), and IDEAL-RT (RTIndex) as 5 kN, 14 kN-mm, and 90, respectively, to avoid premature rutting failure. Thus, the newly developed monotonic Marshall-RT test can also be used as a surrogate simple performance test to estimate the rutting potential of asphalt mixtures during the mix design and plant production phases as quality control (QC)/quality assurance (QA).

Impact of Heavy Vehicle Axle Overload and Axle Configuration on Road Damage in Afghanistan

Aim: This study aimed to determine the percentage of heavy vehicles, overloaded vehicles, and heaviest vehicle that leads to deterioration of asphalt roads. Furthermore, the study aimed to assess the impact of ESALs and axle configuration on asphalt thickness and subgrade.
 Methods: This research used quantitative truck traffic data collected for three months in the Laghman WIM (Weigh in Motion) station located on the Kabul Torkham National Highway. Observed axle loads and GVW (Gross Vehicle Weight) data collected from April/ 10/2022, up to June/7/2022 average daily truck traffic of 73895 was estimated axle loads converted to the standard axle ESALs (Equivalent Single Axle Loads).
 Results: The percentage of heavy overweight vehicles is 13% while the heaviest vehicle is T2-Bedford truck vehicles at 20.17%. The T2 Bedford truck percentage was 42.17% in overall volume; this truck was overloaded 20.17%, compared to the general trend of Ministry of Public Works (MoPW), the T3 Hino truck contribution was 1.24% in total volume and 18.64% was overloaded, the ST112 semi-trailer contributed 3.02% in total volume, and 8.52% were overloaded. The ST113 5-axle and TT123 6-axle trailers percentile in entire volume was 9.6 % and 40.85% whereas, the overloading degree for these heavy vehicles was 2.29% and 6.72% respectively.
 Conclusion: Overloading percentage is 13% while, T2 Truck is the heaviest vehicle The variation of ESALs and axle configuration on asphalt thickness and subgrade modulus illustrates the higher thickness of asphalt decreases the damage to asphalt roads.
 Recommendations: Afghanistan Weigh-in-Motion stations need professional employees, internet facilities, electricity, and proper databases to record the data. By applying tight legislation and fines overloading will be minimized. Researchers may also research heavy vehicle tires' impact on road damage. Furthermore, it needs to determine the level of fatigue cracking and rutting failures by overloading.

Generation of traffic input for flexible pavement design

Layered elastic theory (LET) was performed by Burmister. It helped to build mechanistic – empirical (M-E) pavement design. In this study, three different approaches were used to predict Cumulative Equivalent single axle load (C-ESAL) over the design period. Two were based on M-E and one was empirical. In each of these cases, standard axle loads were used as well as weight limits and vehicle classification, according to their axle configurations (single, tandem, tridem). Traffic data came from annual traffic census campaigns over the past ten years. Gross vehicle weight (GVW) and axle weight (AW) data came from a fixed weighing station performed during 31 days in 2020. Two road axis were considered: One having a weighing station (reference road) and one under technical studies (specific road). Traffic road data were used to perform regression analyses and predictions. AW and GVW helped to calculate Axle load equivalency factors (ALEF) and Truck equivalency factors (TEF) on the reference road. These values were projected on the specific road. Frequency distribution, gross vehicle weight distribution, axle load distribution of heavy vehicles are applied on the reference road. We performed overload AW and overload GVW analyses. Comparisons were done for the three approaches and an evaluation of technical studies was proposed, including traffic and AW monitoring and management systems. This work came as a basis for the transposition of M-E calculation of traffic inputs, more accurate and used over the passed fifty years, in Higher Income countries, called AASHTO method for USA, LCPC-SETRA method for France, to Cameroon and Sub-sahara African countries, that have been using empirical generation of traffic inputs over the same period, called CEBTP method.

Decision Tree Analysis for Developing Weigh-in-Motion Spectra in the Californian Pavement Management System (PaveM)

Weigh-in-motion (WIM) devices record vehicle axle loads on highways. WIM data include axle loads, inter-axle spacings, vehicle classification, gross vehicle weights, vehicle length, and travel speed. Pavement design, management, and performance studies all require WIM data, directly as a spectrum or indirectly as standard axles. In 2016, 132 WIM devices were operating on California’s highway network, one of the densest and best-maintained clusters in the United States. The University of California Pavement Research Center (UCPRC) has been working with these data since 2002, and it completed the analysis of data collected from 1998 to 2003 in 2008. This research investigated similarities in axle load distributions at the WIM sites and grouped them to generate traffic inputs for pavement design. This paper is an extension of that work, including processing the 2004–2015 data from 80 WIM sites, identifying the axle load distribution for each site, updating the original groupings, and developing a new procedure to assign WIM spectra to other locations. For the past 11 years, axle loads and gross vehicle weight showed similar patterns, but average truck speeds decreased by 11%. A combination of clustering and cut-tree analysis was used to create a decision tree to classify the stations’ data into five WIM axle load spectra. The methodology has been used to compute traffic for the entire network used in the Caltrans pavement management system, PaveM. An application tool was also developed for generating truck traffic input files for the CalME and PavementME design tools.

SIMPLIFIED MECHANISTIC – EMPIRICAL ANALYSIS OF FLEXIBLE PAVEMENT

Pavement stress-strain analysis is an ideal tool for analytical modelling of pavement behaviour and thus, constitutes an integral part of pavement design and performance evaluation. It is the fundamental basis for the mechanistic design theory. Predicting pavement response by simplified procedure analysis by relying on equivalency factors using axle load spectrum which is obtained from Weigh-In-Motion (WIM) data is aimed for this study. The framework for computing the structural response of the standard axle group loads on a pavement structure by using a layered elastic computer program and calculation of pavement responses for axle load distribution for different axle groups and axle types by using the theoretical analysis. From the study, the summary of the obtained results are as follows: (1) axle load distribution was developed for the four considered axle configurations; (2) Single axle with single tyre has the greatest destructive impact followed by the tridem axle with dual tyres (TRDT) and next by TADT. The least destructive axle group type is the Single Axle with Dual tyre SADT.The predicted pavement response by theoretical analysis indicates that the critical tensile strains obtained results are all greater than the critical vertical strains. At the heaviest axle load, from 70KN, for both SAST and SADT; from 140KN for TADT; and from 210KN, the critical strains have the greatest magnitude by SAST and followed by SADT and next by TADT. The least critical tensile strain is from the TRDT.

ДОСЛІДЖЕННЯ СТІЙКОСТІ ДО УТВОРЕННЯ КОЛІЇ ТЕПЛИХ АСФАЛЬТОБЕТОННИХ СУМІШЕЙ НА ОСНОВІ БІТУМУ З ВИКОРИСТАННЯМ ЕНЕРГОЗБЕРІГАЮЧИХ ДОБАВОК ТА СПІНЕНОГО БІТУМУ З ДОДАВАННЯМ РЕГЕНЕРОВАНОГО АСФАЛЬТОБЕТОНУ

Introduction. The article investigates asphalt mixtures produced by standard technology according to [1, 2] and the so-called warm asphalt mixtures produced at reduced process temperatures based on bitumen with the addition of energy-saving additives and foamed bitumen. Problems. The resistance of asphalt mixtures to rutting is a key parameter in the design of the mixture, as the load on the pavement structure is increasing under current conditions due to the increased transport capacity of new vehicles that can carry loads with higher than standard axle loads. Objective. The aim of the study was to investigate asphalt mixtures made using standard technology according to [1, 2] and the so-called warm asphalt mixtures made at reduced process temperatures based on bitumen with the addition of energy-saving additives and foamed bitumen. Materials and methods. Experimental comparative tests of traditional hot asphalt concrete ASG.Sh.N.I.A.BND 70/100, asphalt concrete using foamed and bitumen, and asphalt concrete based on bitumen with the addition of energy-saving additives were carried out. Results. Graphical dependences of rut formation after more than

Field investigation of material layer properties for emulsion-treated base layer application in low-volume roads

ABSTRACT The study presents the determination of pavement design input parameters-structural layer coefficients and back-calculated layer moduli for Emulsion-Treated Base (ETB) layer materials in a Low-Volume Road (LVR) application. Seven test sections were constructed on a stretch of LVR with varying emulsion contents and 50% Recycled Asphalt Pavement (RAP) aggregate incorporation in ETB mixes. Structural performance of the test sections was periodically observed using a Benkelman Beam Deflectometer (BBD) and the data was used for the estimation of the structural layer coefficient of ETB, based on the effective structural number of the pavement. The deflection bowl data of the test sections were also captured using a Falling Weight Deflectometer (FWD) and the modulus of ETB layer was back-calculated using a back-calculation software. The study proposes a structural layer coefficient of 0.23–0.29 and back-calculated moduli of 578–919 MPa for ETB mixes characterised by Indirect Tensile Strength (ITS) values ranging between 140 kPa and 245 kPa. Traffic level-based ETB mix specifications are also proposed in the study, which enables a mix designer to proportion the mix for a selected design traffic level. For a design traffic level of 1 million standard axles, the target dry ITS specification was found to be 188 MPa.

A study on the lane validating the distribution factor on urban and rural highways

A critical aspect of designing road pavements is accurately estimating the expected traffic load. It's important to note that not all vehicles use the same wheel path when traveling on a road. Many factors, including the Lane Distribution Factor (LDF), can affect the lateral shift of the load applied to the pavement. LDF is a crucial factor in designing flexible pavements, as it helps transportation planners and highway engineers estimate lane usage relative to the total traffic volume. This information is essential for understanding how pavements respond to wheel loads and fatigue behavior. The IRC: 37 - 2018 guidelines provide a set of LDFs for estimating the design traffic in terms of Million Standard Axle Loads. However, to ensure the accuracy of these LDFs, a study was conducted on rural and urban highways with two and four lanes to identify the lateral distribution of the vehicles.

An Italian road pavement design method for bus lanes: proposal and application to case studies

In urban centres, the presence of bus lanes is essential to facilitate public transport services for a better sustainability of the cities and reduction of private traffic and pollution. However, bus lanes need a specific geometric (i.e. road layout) and structural (i.e. pavement layer thickness) suitable design. The pavement design of bus lanes in urban areas is often performed using traditional methods, already used for other types of roads. Given the geometric and structural peculiarities of each road in the urban centres due to the historical city development, the application of these methods can lead to an incorrect road pavement design.For this purpose, a first attempt of a road pavement design system has been developed for bus lanes: it is a specific catalogue proposal for this type of lanes, which can support the technicians in evaluating the most appropriate solutions in terms of materials and thickness, for both new construction and maintenance.After evaluating the types and main characteristics of buses circulating in Italy, traffic levels (in terms of equivalent standard axle loads), subgrade bearing capacity and pavement structure were hypothesized. Assuming three possible structures and five traffic levels, a total of forty-four design solutions were drawn up. The required pavement thickness varies from 17 to 47 cm for a new lane construction and from 9 to 22 cm for an existing lane maintenance.All the proposed solutions have been verified by methods and models based on multi-layer elastic theory available in the literature. Moreover, their validity was evaluated applying the solutions to real cases. The results of this work encouraged the authors to improve the catalogue inserting solutions with natural stone, particularly used in historic centres for architectural and aesthetical reasons, and to differentiate the pavement thickness of bus lanes subject to high stresses (intersections, stops, etc.).

Thickness and Cost Comparison of Cement Treated and Granular Base for Flexible Pavement: A Case Study of Pathlaiya-Nijgadh Section of East-West Highway of Nepal

A pavement is considered a multi-layer system that distributes the vehicular load over a large area and transfers it to the foundation. Flexible pavement is mainly deteriorated due to the failure of its layer as well as the subgrade soil. Resisting the vehicular load requires the appropriate thickness of the sub-base and base with optimization of cost. This study aims to find the effect of the cement-treated base on thickness, unit cost, and life cycle cost. Design traffic was estimated for 15 years design period with an annual traffic growth rate of 5% for the Pathlaiya-Nijgadh Section of the East-West Highway of Nepal. The thickness of the granular base and the cement-treated base was 500 mm and 357.43 mm for design traffic of 34.86 million standard axles (msa) and the total pavement thickness for design traffic of 34.86 msa was 590 mm and 457.43 mm respectively. The comparison of cost estimates for the base course revealed that there was a 5.63% reduction in the per km cost of the cement-treated base as compared to the granular base. The cement-treated base seems to be a viable alternative to the base course for road construction as compared to the granular base. The pavement maintenance using a Cement-Treated Base (CTB) was 47.31% more economical than pavement maintenance using a granular base course. The total cost including initial investment and the cost of the maintenance of the pavement construction using CTB was 24.39% lower than that of the granular base.

A Surface Texture Prediction Model Based on RIOHTrack Asphalt Pavement Testing Data

The surface texture of asphalt pavement is of enormous importance to skid resistance. To investigate the degradation tendency of surface texture related to the skid resistance, four years of sensor measured texture depth (SMTD) panel data measured from 19 pavement structures including 4 types of surface asphalt layer are used to develop a surface texture prediction model. The panel data-based prediction model takes into account the dependence on time scale, diversified road sections, traffic factors, environmental factors, and the Bailey method-based aggregate gradation parameters. The regression and prediction capability of the surface texture model is evaluated from both short and long-term perspective. The results indicated that the random-effects model is the most suitable form to characterize the degradation of surface texture. The cumulative standard axle loads (CSAL), monthly average humidity (MAH), and the Bailey method-based aggregate gradation parameters (the coarse aggregate ratio (CA), the fine aggregate coarse ratio (FAC), and the fine aggregate fine ratio (FAF)) have significant influences on the sensor measured texture depth. The time scale of the input sensor measured texture depth (SMTD) data has influence on the accuracy of the surface texture prediction model; therefore, long-term data series can ensure the robustness of long-term prediction. The results of this study can benefit the material design, construction, maintenance of asphalt pavement, and its evaluation pavement for longer service life.