Bearing Capacity Of Pavement Research Articles

The Study on a New Composite Road Panel Structure

<p class="p0">A kind of composite precast pavement system made by two composite and staggered layer panel is put forward, the finite element analysis software ANSYS is used to analyze the pavement system, and the calculation result is compared with the result of common precast pavement system. It shows that the proposed pavement system can greatly reduce the surface earth pressure, thus to improve the bearing capacity of pavement, and provide a new pavement structure system for the construction of site temporary road paving.</p>

Application of GPR and FWD in Assessing Pavement Bearing Capacity

Abstract The process of pavement maintenance and rehabilitation starts by collecting the data which will form the base for evaluation of pavement functional and structural condition. Collection of data can be performed by destructive and non-destructive testing. Usually preferred are the non-destructive methods, that do not damage the pavement, and the process of pavement evaluation is objective and repeatable. Non-destructive testing methods are becoming more and more popular, especially for assessing the structural condition of the pavement. Non-destructive testing by a Falling Weight Deflectometer (FWD) and the analysis of so collected data by the process of backcalculations is today the usual tool for assessing pavement bearing capacity. One of the basic input parameters for analysis of the data collected by FWD is pavement layers thickness. The practice in Croatia is to determine pavement layers thickness by coring. This destructive method affects pavement integrity, so the number of such tests should be kept to the minimum. By coring the accurate thickness of all pavement layers is obtained on specific point locations. Thus, numerous deviations in layer thickness remain unnoticed, and in the end, use of such data for the process of backcalculations does not provide ac urate values of layer moduli. Coring can be replaced with non-destructive method of testing by Ground Penetrating Radar (GPR), which provides continuous information on thickness of all pavement layers. The paper shows the method for assessing the bearing capacity of the pavement based on the data collected by FWD, GPR and coring. The calculation for layer moduli was performed by the ELMOD software, separately for the layers thickness data obtained by coring, and separately for the thickness obtained by GPR tests. Analysis and comparison of the results of calculated elasticity moduli obtained by using various methods for collecting layer thickness data were performed in the paper.

The Potentials of Portland Cement and Bitumen Emulsion Mixture on Soil Stabilization in Road Base Construction

Recycled road based material requires a stabilizing effect in order to provide a longer life to pavements. This is done by improving its strength and reduces its water vulnerability. One of the most popular techniques to achieve this is by using soil stabilization. This research aims to analyze in details the soil stabilization method which utilizes Portland cement and bitumen emulsion in improving soil properties. As a result, this will increase the pavement bearing capacity (conducted via laboratory research). The combination of Portland cement and bitumen emulsion are beneficial for the purpose of increasing the stiffness and also the elasticity of soil stabilized layer. In order to examine this, two steps were undertaken, first, by examining the Unconfined Compressive Strength (UCS) and Modulus of Elasticity (ME) on samples mixed with soil aggregates comprising Portland cement and bitumen emulsion. Next, the data collated was analysed and the graph plots were presented as to show the optimum value of Portland cement and bitumen emulsion used in soil stabilization. The major findings of this research showed the importance of soil stabilization using Portland cement and bitumen in improving pavement’s performances by increasing bearing capacity of its layer. The findings revealed that overall; the optimum value of Portland cement and bitumen emulsion utilized in base Soil stabilization method is 3% and 3% respectively. With this method, the duration time of the project can be reduced and subsequently the project cost may be also reduced.

Cyclic Approach to Airport Pavement Management Based on Non-Destructive Deflection Testing

The Authors describe the role of non-destructive deflection tests in Airport Pavement Management System (APMS) presenting the experience developed at an Italian Airport. An original approach to APMS implementation is illustrated, based on the PDCA cycle for quality control and continuous improvement of processes. An example application for the management of the runway pavement is described. Deflection test results obtained in four tests campaign carried out over a ten years period were globally analyzed to obtain pavement bearing capacity evolution and demonstrate the effectiveness of cyclic approach to pavement management. It is showed that structural evaluation can be an invaluable tool in pavement management and assist planning activities in the medium and long term.

Bitumen-cement Stabilized Layer in Pavement Construction Using Indirect Tensile Strength (ITS) Method

In this study, the objective was to blend and mix Portland cement and bitumen emulsion with soil for enhancing the strength, durability and pertinent properties of the soil. In order to enhance the soil strength and lessen its vulnerability to water, soil stabilization is required to be applied to the soil. In line with this, improved load transfer was added to the pavement foundation by having the cement effect which actually boosts the stiffness and Bitumen emulsion effects which improve resilience and soil permeability of the stabilized layer. The current study is divided into two phases. In the first phase, the optimization of Portland cement and bitumen emulsion was preformed as well as conducting a series of Indirect Tensile Strength (ITS). Furthermore, in order to lessen the pavement’s thickness and to enhance its bearing capacity, alternative roadway sections were scrutinized through the second phase. The results proved that soil stabilization with cement and bitumen enhances the bearing capacity of pavements in two chief areas. Primarily, there was enhancement in pavement’s lifetime and the more efficient construction time is achieved.

Investigation of a pavement structural behaviour during spring thaw using falling weight deflectometer

The response of an instrumented flexible pavement structure in southern Sweden, subjected to seasonal freeze–thaw cycles, was investigated during the spring thaw and the recovery periods in 2010. The pavement environmental condition was continuously monitored by measuring subsurface temperature and moisture contents. The mechanical behaviour of the pavement structure was investigated by conducting frequent falling weight deflectometer (FWD) measurements throughout the study period. Considerable decrease in the pavement-bearing capacity was observed as thaw penetrated the pavement structure and consequently moisture content increased in all pavement unbound layers. Highest annual moisture content in the subgrade upper section was registered as thaw penetrated the subgrade and pavement exhibited its weakest structural condition. The analyses of the deflection basin indices and back-calculated unbound layer stiffness from the FWD measurements exhibited a clear correlation with the measured subsurface moisture content. Furthermore, the dissipated energy measured from the FWD time–history data was calculated, exhibiting its highest annual value during the thawing period. Using the back-calculated layer stiffness and moisture measurements in unbound layers, a degree of saturation-based moisture-stiffness model was developed for the granular layer and the subgrade. This model fell on a unique curve showing promising agreement with the laboratory-based model proposed by Mechanistic-Empirical Pavement Design Guide that analytically predicts changes in modulus due to changes in moisture.

A Method for Temperature Correction of HMA Dynamic Modulus

HMA dynamic modulus is one of key inputs to the Mechanistic-Empirical Pavement Design Guide. In order to analyze and evaluate bearing capacity of asphalt concrete pavement and to determinate the rules of pavement deterioration of modulus of asphalt layer under repeated wheel load and ambient, temperature correction for HMA is applied to the modulus so as to compare them with the same temperature. In order to get temperature correction coefficients for HMS moduli, a method of temperature correction for HMA moduli was put forward. In this method, the specimen of asphalt mixture or HMA cores from in-situ pavements were tested by Superpave Simple Performance Tester(SPT), or falling weight deflection(FWD) was tested on the site of in-situ pavements. The correlation between HMA dynamic modulus and temperature was regressed, and then dynamic modulus regression model was put forward. Results show that exponential function was fitted to the data to determine and adjust the modulus to a reference temperature, the recommendation regression equation can reflect the features of asphalt mixture at the reference temperature.

Change of Bearing Capacity Characteristics of Asphalt Pavement

Time succession of data for monitored variable parameter of pavement state is the first step in development of degradation models and determination of degradation functions. Procedure used for characteristics of bearing capacity is described in the paper.Data from long time monitored (since 1995) test section on road network were used. First of all homogeneity of subgrade was tested. The deflections at distance of 1500 mm from load centre were used for this purpose. Data that met criteria of homogeneity were corrected taking into account influence of temperature. Two characteristics of bearing capacity (central deflection and surface curvature index) were evaluated in relation to number of heavy vehicles that had passed test section.Results showed that investigated characteristics of pavement bearing capacity changed in time. It was stated that tendency of development was not very clear because values oscillated in the narrow range. Generally saying the bearing capacity of tested pavement has not changed since 1995 significantly.

Development of Roughness Prediction Models for Low-Volume Road Networks in Northeast Brazil

Roughness evaluation is the most effective way to diagnose pavement condition for design and decision making. The index most commonly used worldwide to indirectly describe the surface condition of asphalt pavements is the international roughness index (IRI). However, few studies have tried to predict the pavement performance of low-volume roads (LVRs) on the basis of the IRI, especially for LVRs in tropical regions. In an attempt to remedy that lack of knowledge, this paper presents IRI-based prediction models developed for asphalt pavement LVR networks in northeast Brazil. The following independent variables were considered to affect the IRI: Thornthwaite's aridity index, which describes local climate; the modified structural number, representing pavement bearing capacity; and the cumulative number of equivalent single-axle loads, representing the traffic applied to the pavements. A multiple regression analysis was carried out, and the results showed that the IRI increases exponentially over time. The analysis of the model parameters confirmed their significance, and the R-square values were 0.87 and 0.94, respectively, for low-volume roads with hot asphalt mixes and bituminous surface treatments. The hot-mix asphalt model was compared with that of the Highway Development and Management Model and with other models developed in research also sponsored by the World Bank. Because of regional differences (especially climate and materials), the models proposed in this paper provide a better estimation of roughness progression in LVRs of the northeast of Brazil.

Research on Adaptability of Semi-rigid Material as Base Course for Long-life Asphalt Pavement

AbstractIn the light of semi-rigid material as base course for perpetual asphalt pavement, the bearing capacity and fatigue life of asphalt pavement with semi-rigid base cause and different asphalt...

Use of FWD Deflection Basin Parameters (SCI, BDI, BCI) for Pavement Condition Assessment

Current research studies relationship between Falling Weight Deflectometer (FWD) deflection basin parameters and road pavement structural condition indicators, such as fatigue cracking and permanent deformations induced by low bearing capacity of pavement, and pavement equivalent E modulus (Eeq). The primary aim of the research was to develop limit values for deflection basin parameters: surface curvature index (SCI), base damage index (BDI) and base curvature index (BCI). Analyses of data derived from the Estonian Road Databank disproved the hypothesis of relationship between deflection basin parameters and pavement defects or rutting. Deflection basin parameters and back-calculated Eeq were found to be in good correlation. Strong relationships were found between upper layers indicators (SCI and BDI) and Eeq. Relationship between subgrade indicator BCI and Eeq, found in the research, was not very strong. Based on the aforementioned relationships, and the required min equivalent modulus of particular pavement, the equations to determine the limit values of deflection basin parameters for different types of pavements were developed. As the statistical analyses of such extensive database have been done for the first time in Estonia, the determined limit values have to be evaluated in practice and, if needed, corrected.

Base Course Modification through Stabilization using Cement and Bitumen

The main objectives of this research was to analyze the use of combined cement and bitumen emulsion in base course stabilization in details and examine its replacement with conventional pavement in regions with low quality materials and limited construction period. To conduct the objectives, the research divided into three phases. Phase I involved the optimization of cement and bitumen emulsion. In this case, a series of Indirect Tensile Strength (ITS), Unconfined Compressive Strength (UCS) and Marshal Tests carried out. In the second phase, various alternative roadway sections examined for minimizing the pavement thickness and increasing the bearing capacity and finally in third phase, a Falling Weight Deflectometer (FWD) machine used to examine the pavement bearing capacity for three sections of the roadway. It was found that, the optimum values to eliminate the creation of shrinkage cracks in the whole project and minimize the execution period and construction costs were 3% for both binders in stabilization and its replacement with conventional pavement method (i.e., stabilized layer with conventional sub-base and base layers). Also, FWD results showed that, the bearing capacity of the constructed pavement using stabilization method is far beyond the predicted values in pavement design. Furthermore, it was found that, with high inflation rate and political situation in the region, base stabilized method decreased the final roadway construction costs in compare with conventional pavement method.

Pavement Diagnosis as Integrant of the Pavement Management System

The paper integrates the most important scientific information of the authors in the field of diagnostics of road pavements. Basic attributes of pavement serviceability (evenness, skid resistance) and pavement bearing capacity are the core of the paper. The results of simulations of dynamic systems, outputs of the models developed at the authors place, the correlations to the world established parameters of evenness and skid resistance are presented in the paper. Objective scientific outputs have formed an effectual base for development the Slovak Pavement Management System (PMS). The principles of the Slovak PMS are described.

Rating the Aircraft Load and Reporting the Bearing Capacity of Rigid Airport Pavements

ABSTRACT Successful management of airport pavements presumes the existence of a suitable procedure for the structural classification and the continuous monitoring of their bearing capacity. According to the modern trend, it is necessary to utilise a pavement to the maximum extend without risking not only the safety of the flights but also the cost of economic penalties which might arise from busy airports' closures for extensive repairs. Practical applications have shown that the worldwide used classification procedure, the ACN-PCN of ICAO, is inadequate for this; consequently an alternative proposal is introduced and presented in this paper aiming to provide the basis of a methodology for classifying rigid airport pavements and checking their structural adequacy. Investigation of the proposed approach showed that it can be more effective than ACN-PCN since it is compatible with the majority of methods currently used for airport pavement design, evaluation and maintenance. Preliminary application using field data indicates that the proposed approach has several advantages and can be a useful tool for pavement managers and engineers.

Rating the Aircraft Load and Reporting the Bearing Capacity of Rigid Airport Pavements

ABSTRACT Successful management of airport pavements presumes the existence of a suitable procedure for the structural classification and the continuous monitoring of their bearing capacity. According to the modern trend, it is necessary to utilise a pavement to the maximum extend without risking not only the safety of the flights but also the cost of economic penalties which might arise from busy airports' closures for extensive repairs. Practical applications have shown that the worldwide used classification procedure, the ACN-PCN of ICAO, is inadequate for this; consequently an alternative proposal is introduced and presented in this paper aiming to provide the basis of a methodology for classifying rigid airport pavements and checking their structural adequacy. Investigation of the proposed approach showed that it can be more effective than ACN-PCN since it is compatible with the majority of methods currently used for airport pavement design, evaluation and maintenance. Preliminary application using field data indicates that the proposed approach has several advantages and can be a useful tool for pavement managers and engineers.

The Linear Matching Method for Shakedown and Limit Analyses Applied to Rolling and Sliding Point Contact Problems

ABSTRACT An understanding of the load bearing capacity of road pavements requires insight into the load levels at which incremental plastic strains occur under rolling contact. A number of authors have described solutions of this problem in terms of shakedown limits, assuming particular simple classes of plastic deformation patterns and using the upper bound shakedown theorem. In this paper we describe a general numerical technique, the Linear Matching Method, for evaluating the shakedown limit under rolling contact including surface friction where the mechanism at the shakedown limit may be described by any finite element discretization. In this way, very accurate shakedown limits may be evaluated. Comparisons are made with the semi-analytical solution of Ponter, Hearle and Johnson [PON85] for a von Mises yield condition, as a first step towards the development of such methods for pavement design.

Bearing Capacity and Structural Classification of Flexible Airport Pavements

Due to the large variety in aircraft types and loads, the use of a comprehensive rating system for the aircraft loads and the bearing capacity of the pavements has been an obligation of airport authorities. Among the major features of such classification systems is their relation to the structural performance and the bearing capacity of pavements. However, implementation of today’s official rating system, the aircraft classification number–pavement classification number developed by the International Civil Aviation Organization, has shown that in many cases, it is difficult to incorporate the information given by modern procedures currently used for the analysis and evaluation of performance of airfield pavements. The reporting often fails to reflect the actual bearing capacity of the pavement within the high standards set by several modern approaches used for airport pavement design and evaluation. In this work, an attempt to improve the correlation of pavement strength reporting with the bearing capacity is presented and discussed.

Performance of Geosynthetic-Reinforced Asphalt Pavements

This paper describes the performance of geosynthetic-reinforced asphalt pavement under monotonic, cyclic, and dynamic loading conditions. The study differed from current practice where geosynthetics are typically used as separators or to improve the bearing capacity of the subgrade. A geogrid layer was installed at the bottom of the asphalt concrete layer, along the asphalt-subgrade interface, to function as tensile reinforcement. The load was applied to the surface of the asphalt concrete layer using a rigid rectangular footing under plane strain conditions. The strains that developed along the geogrid over time and at different load levels were monitored. Two different types of geogrid reinforcements were used, and their restraining effects on the layered system were compared. The study showed that geosynthetic reinforcement increased the stiffness and bearing capacity of the asphalt concrete pavement. Under dynamic loading, the life of the asphalt concrete layer was prolonged in the presence of geosynthetic reinforcement. The stiffness of the geogrid and its interlocking with the asphalt concrete contributed to the restraining effect.

An Alternative Proposal for Reporting the Bearing Capacity of Flexible Airfield Pavements

Structural classification of airfield pavements has always been of great importance for the establishment of a comprehensive airfield pavement management system. As the use of a simple and reliable classification procedure can significantly help the airport authorities to monitor the performance of their pavement(s) and plan an effective maintenance program, the existence of a structural classification procedure that can classify, check and estimate the pavement bearing capacity on a long-term basis could be a useful tool. In addition to this, the procedure presented in this work can easily co-operate with modem analytical design and evaluation procedures, in contrast to classical methods used for the structural classification of airfield pavements.

Thaw weakening of pavement structures in cold regions

Although considerable efforts have been spent on studying the effects of seasonal frost conditions on pavement performance, the effects of thaw weakening have been less extensively investigated. This paper presents a review of the literature with regard to soil thawing and bearing capacity of pavements during thaw weakening periods. The reviewed literature indicates a large number of parameters affecting the extent of weakening during spring thaw. Soil type, permeability, drainage conditions and rate of thaw are generally regarded as some of the most important factors. However, the relative importance of these factors are unclear, and the literature, concerning large scale field tests indicates considerable differences in pavement performance during thaw weakening.