The Structural Performance Of A Pavement Construction Essay

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The structural performance of a pavement relates to its physical condition in terms of distresses and other conditions that would reduce its load carrying capabilities. The structural evaluation is undertaken to assess the pavement's structural ability to receive the loads plying over it. This is also needed to design maintenance and rehabilitation measures to meet the future requirements. The functional performance, on the other hand, relates to how well the pavement serves the user. The functional evaluation is being conducted to assess the riding comfort and safety over the pavement section as experienced by road users. At the project level it might be appropriate to evaluate the distresses individually, but at the network level definition of some kind of composite measure of performance (performance indicator) is necessary. Thus the issue is how one evaluates flexible pavement's present and future functional and structural health. Also since all sections in a network needs to be evaluated and that too routinely, the evaluation procedure must be quick, cheap and simple, yet effective.

Another important but much neglected parameter which affects the structural and functional characteristics of the flexible highway pavement is subsurface drainage. Subsurface drainage is an important feature in determining the flexible pavement performance. The ability of a pavement to withstand the effects of traffic and environment will depend upon the drainage quality of the flexible highway pavements. Drainage affects the strength and behaviour of both the subgrade soil layer and the granular base course layer and also the durability of the bituminous courses. An increase in moisture content decreases the strength or stability of a soil mass, and also affects the highway performance adversely. Adequate drainage is a primary requirement for maintaining the structural soundness and functional efficiency of a road. Sustained long period of water staying within a pavement system is undesirable because the free water can not only adversely affect the load carrying capacity of the pavement but also cause premature pavement failures.

A pavement maintenance system should have the ability to perform present pavement performance evaluation and future performance prediction. Pavement performance is determined by both severity and extent of distress. The distresses occurred on the pavement surface are considered as the major performance indicators of the in-service pavements. Pavement distress manifestations are visible pavement surface deterioration or failures, which result from the damaging effects of traffic and environment over time. Pavement performance evaluation of flexible highway pavements needs to be carried out periodically as part of pavement management system for identifying and prioritizing the pavement rehabilitation and maintenance needs both at project level and network level.

The present research work has a focus on the development of a comprehensive methodology for evaluation of performance of flexible highway pavements in India. It includes a methodology for evaluation of performance of individual distress condition, a methodology for performance evaluation of an overall structural condition and another methodology for performance evaluation of the overall functional condition. In this study, various indices are developed for the assessment of individual distress condition, overall structural condition and overall functional condition. These indices can be used to compare different sections for maintenance need of individual distress condition and to compare different sections for a network level analysis. These indices can also be used to compare different sections for determining maintenance priority.

Pavement engineers have long recognized the necessity of good drainage in the design and construction of the flexible pavements. Drainage is an important feature in determining the ability of a pavement to withstand the effects of traffic and environment.The existing pavement performance models are suitably modified so that the effect of drainage quality can also be evaluated explicitly in predicting future performance of individual distress condition. The assessment of the health of the flexible pavements considering the effects of drainage quality, saturation time, pavement age and traffic is also dealt with in the present work. The methodology proposes simple (i.e. easy to use by field maintenance personnel), quick and cost-effective process (i.e. can be executed with minimal data), most suitable for developing countries like India. A point to be noted here is that in the above study it is assumed that no maintenance strategy is adopted.

Problem Statement

In any flexible highway pavement network, one of the major tasks is the evaluation of performance of the roads in the network. Every year the condition of the road deteriorates and every year the engineer has to decide how best to improve these roads given the limited resources available. In this thesis the problem of the performance evaluation of the flexible highway pavements is looked into. The issues which needs to be addressed are how to assess the individual distresses so that the maintenance needs of the individual distresses can be assessed, how to assess overall structural performance, how to assess overall functional performance so that analysis at network level can be done and how to develop the methodology to evaluate the individual distress condition, overall structural condition and overall functional condition in a simple, cost effective manner as well as incorporating the effect of drainage quality of the flexible highway pavements.

In order to maintain any existing highway network, a prior systematic assessment of the present condition of the highway network is required, for such assessment resources are required not only in terms of the money but also in terms of other resources such as equipment and manpower. Typically, and this is especially true for developing countries like India, resources are inadequate for carrying out such systematic assessment of the present condition of a highway network. Thus one of the issues here is, given the sections and their characteristics (in terms of drainage quality, traffic and distress condition etc.) how does one evaluate its present individual distress condition, present overall structural condition and present overall functional condition. The prediction of future condition of a highway network needs to be done and that too by incorporating the much neglected drainage quality parameter. The evaluation of the present condition and the prediction of the future condition of a highway network give the overall condition of the highway network. Since the performance of all the sections in a network needs to be evaluated and that too routinely, the evaluation procedure must be cheap and simple, yet effective. In this thesis, therefore the following issues/tasks have been taken up and methodologies have been proposed.

Evaluation of present individual distress condition of a highway section quickly and effectively.

Prediction of future individual distress condition of a highway section by incorporating the much neglected drainage quality parameter.

Evaluation of overall individual distress condition of a highway section.

Evaluation of present structural condition of a highway section quickly and effectively and without using any sophisticated equipments.

Prediction of future structural condition of a highway section by incorporating the much neglected drainage quality parameter.

Evaluation of overall structural condition of a highway section for network level analysis.

Evaluation of present functional condition of a highway section quickly and effectively.

Prediction of future functional condition of a highway section by incorporating the much neglected drainage quality parameter.

Evaluation of overall functional condition of a highway section for network level analysis.

The above issues/ tasks have been discussed at length in latter chapters.

Objectives and Scope of the Study

1.3.1 Objectives of the Study

The main objective of this research work is to carry out studies to develop a comprehensive methodology for evaluation of performance of flexible highway pavements in India. Such comprehensive methodology includes a methodology for evaluation of performance of individual distress, a methodology for performance of an overall structural condition and another methodology for performance of the overall functional condition. Therefore, there is a need to develop following three different methodologies to achieve the objective of this study. Thus, the objectives of the study are identified as follows:

1.3.1.1 To develop a simple methodology for performance evaluation of individual distress condition commonly occurring on flexible highway pavements in India i.e. A Methodology for Performance Evaluation of Individual Distress condition.

1.3.1.2 To develop a simple methodology for performance evaluation of overall structural condition of flexible highway pavements in India i.e. A Methodology for Performance Evaluation of Overall Structural Condition.

1.3.1.3 To develop a simple methodology for performance evaluation of overall functional condition of flexible highway pavements in India i.e. A Methodology for Performance Evaluation of Overall Functional Condition.

1.3.2 Scope of the Work

To achieve the above objectives, the scope of the work of this PhD work is identified as follows:

1.3.2.1 Development of a Methodology for Performance Evaluation of Individual Distress condition

Development of a simple methodology for evaluation of present condition of an individual distress condition.

Development of a simple methodology for measurement of severity of a particular distress on different pavement sections in the network. It is required that methodology should be simple so that it can measure the severity of different distresses without using sophisticated equipments and quickly. This performance evaluation is required because different severity will require different maintenance treatment.

Determination of relative importance (weights) of distress condition of different severity (i.e. low, medium and high severity distress condition). It needs to be determined so that maintenance needs of different distress condition can be identified and prioritized.

Development of a simple methodology to combine present condition of different severity distress condition. It is required to develop an appropriate present performance index for evaluation of individual distress condition incorporating their extent, severity and relative importance. This index can be used to compare different sections for maintenance need of individual distress condition.

Development of a simple methodology for prediction of future condition of an individual distress condition.

Development of a simple methodology for prediction of extent of a particular distress condition. It is especially required to suitably modify the existing pavement performance models so that the effect of drainage quality can also be evaluated explicitly in predicting future performance of individual distress condition.

Development of a simple methodology to combine future condition of different severity distresses and development of index to compare different sections for a network level analysis.

Development of a simple methodology to combine future condition of different severity distress conditions. It is required to develop an appropriate future performance index for evaluation of individual distress condition incorporating their predicted extent, severity and relative importance.

Development of a simple methodology for performance evaluation of overall individual distress condition. It is required to develop an appropriate overall individual distress condition index combining present individual distress condition and future individual distress condition. This index can be used to compare different sections for determining maintenance priority of individual distress condition.

Analysis and results using proposed methodology to illustrate how efficiently the methodology is working using a flexible highway pavement network data.

1.3.2.2Development of a Methodology for Performance Evaluation of Overall Structural condition

Development of a simple methodology for performance evaluation of present structural condition. It is required that methodology should be simple so that it can measure the severity of different distresses quickly and without using sophisticated equipments. This is required to identify maintenance needs of different sections.

Development of a simple methodology for performance evaluation of future structural condition. This is required to identify maintenance needs of different sections.

Development of a simple methodology for performance evaluation of overall structural condition. It is required to develop an appropriate overall structural condition index combining present structural condition and future structural condition. This index can be used to compare different sections for determining maintenance priority.

1.3.2.3 Development of a Methodology for Performance Evaluation of Overall functional condition

Development of a simple methodology for performance evaluation of present functional condition.

Development of a simple methodology for performance evaluation of future functional condition.

Development of a simple methodology for performance evaluation of overall functional condition. It is required to develop an appropriate overall functional condition index combining present functional condition and future functional condition. This index can be used to compare different sections for determining maintenance priority.

Organization of the Dissertation

In this section, the organization of the thesis is explained briefly. The thesis is divided into eight chapters of which this is the first. The thesis also contains two appendices.

Chapter 2 presents a review of past studies relevant to the problem considered in this thesis. The chapter presents a critical review of literature relevant to factors affecting the performance of flexible highway pavements like traffic loading associated factors, pavement composition factors and drainage performance factors. The evaluation of present performance and future performance of flexible highway pavements are also discussed in this chapter.

Chapter 3 presents the proposed methodology for performance evaluation of flexible highway pavements.

Chapter 4 presents the methodology for evaluation of individual distress condition. The present individual distress condition, future individual distress condition and the overall condition of individual distress is determined. Analysis and results of sensitivity analysis of drainage performance is also dealt in this chapter.

Chapter 5 provides an approach to evaluate the overall structural condition of flexible highway pavements i.e. the present structural condition and the future structural condition. This chapter also deals with the overall structural condition of the flexible highway pavements obtained by combining the present structural condition and the future structural condition.

Chapter 6 provides an approach to evaluate the overall functional condition of flexible highway pavements i.e. the present functional condition and the future functional condition. This chapter also deals with the overall functional condition of the flexible highway pavements obtained by combining the present functional condition and the future structural condition.

Chapter 7 shows the analysis and results using the proposed methodology. The study describes how the proposed methodology can be utilized by the highway agencies to evaluate the performance of flexible highway pavements.

Chapter 8 highlights the primary contributions made here. The chapter also presents the recommendations for further research.

This thesis also contains two appendices. The first appendix i.e. appendix A provides the expert opinion questionnaire obtained from transportation professionals. The second appendix i.e. appendix B presents the sensitivity analysis for drainage performance evaluation.

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