SUMMARY This book provides complete coverage of surface and subsurface drainage of all types of pavements for highways, urban roads, parking lots, airports, and container terminals. It provides up-to-date information on the principles and technologies for designing and building drainage systems and examines numerous issues, including maintenance and designing for flood events. Practical considerations and sophisticated analysis, such the use of the finite element method and unsaturated soil mechanics, anisotropy and uncertainties, are presented. This book allows civil engineers to make the best use of their resources to provide cost effective and sustainable pavements. Features Presents a holistic consideration of drainage with respect to pavement performance. Includes numerous practical case studies. Examines flooding and the impacts of climate change. Includes PowerPoint slides which include quizzes, schematics, figures, and tables.

This synthesis will be of interest to geologists; hydrologists; geotechnical, pavement, construction, and maintenance engineers; and researchers. State department of transportation (DOT) program managers and administrators will also find it of interest. The synthesis describes the current state of the practice for the design, construction, and maintenance of pavement subsurface drainage systems. It provides information on the positive effects of good subsurface drainage and the negative effects of poor subsurface drainage on pavement surfaces. This report of the Transportation Research Board presents data obtained from a review of the literature and a survey of the state DOTs. It is a supplemental update to NCHRP Synthesis of Highway Practice 96, Pavement Subsurface Drainage Systems (1982). The synthesis provides a supplement to design issues not found in Synthesis 96, but faced by current designers, e.g., type and quality of aggregate, compaction requirements for open-graded aggregates, asphalt and cement binders, and use of geosynthetics. In addition, it describes the effects of design, construction, and maintenance decisions on the performance of pavement subsurface drainage systems.

This study was aimed at evaluating the performance of pavement drainage systems that can be used in the State of Illinois using locally available aggregate sources for construction of these drainage systems. The study was limited to investigations on the use of open-graded, hot-mixed bituminous aggregate mixtures (OGBAM), for use in the pavement drainage system. A preliminary investigation was carried out in the laboratory to evaluate the permeability and the stability of the OGBAM. Specimens were prepared according to the procedures given by ASTM D 1559, Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus. Permeability test (using a constant-head permeameter that allowed the measurement of permeability at low heads) and stability test were performed on the same specimen. Using the results of the preliminary investigations, six test pavements (4 feet long) incorporating different design concepts were tested in the University of Illinois Test Track. Dynamic loading was applied to the test pavements and water was passed through the OGBAM drainage layers to simulate surface and lateral infiltration. Permeability tests at constant head were carried out regularly on the pavement test sections. The progress of rutting in the test pavements was also recorded. Results of these limited tests indicate that OGBAM possess a very high order of permeability, and that care must be taken to prevent the migration of subgrade fines into the OGBAM layers for satisfactory performance of OGBAM layers with regards to drainage. The report outlines some of the methods that can be used to ensure satisfactory performance of pavements using OGBAM layers.

Following the recommendation of the Virginia Transportation Research Council's Pavement Research Advisory Committee, this project was initiated to determine the effectiveness of including subsurface drainage systems in pavements in Virginia. The researchers sought to determine the effectiveness of these systems by conducting a literature review and by comparing the strengths of pavement sections with and without a subsurface drainage layer in a limited field investigation involving two pavement structures in Virginia. The strength of the pavement structure was analyzed using the falling weight deflectometer. The researchers concluded that the drainage layer appears to affect positively the in-situ subgrade resilient modulus and the in-situ structure number. Further, inclusion of a properly constructed drainage layer does not adversely affect the deflection of a pavement and thus does not introduce a weakness into the pavement structure. However, the condition of the outlet pipes appears to be of high importance. The researchers recommend that tests with additional sites be conducted in the spring when the subgrade moisture is expected to be highest; that the Virginia Department of Transportation (VDOT) develop a maintenance program to maintain functioning drainage outlet pipes; and that VDOT continue the practice of constructing subsurface drainage features on high-priority pavements. In 2005, VDOT anticipates spending approximately $45 million on resurfacing interstate and primary roadways. According to the literature review, the average service life of flexible pavements (time between successive rehabilitation efforts) is approximately 9 years. Including subsurface drainage features offers a 4-year extension of service life (a 44% extension). Thus it can be approximated that the current practice of including subsurface drainage features is saving VDOT approximately $20 million per year. However, the amount of this cost savings may not be fully realized if drainage outlet pipes are blocked or partially blocked. As reported in the literature review, nonfunctioning drains accelerate pavement deterioration and thus may actually shorten the service life of pavement structures.

The purpose of this manual is to provide clear and helpful information for maintaining gravel roads. Very little technical help is available to small agencies that are responsible for managing these roads. Gravel road maintenance has traditionally been "more of an art than a science" and very few formal standards exist. This manual contains guidelines to help answer the questions that arise concerning gravel road maintenance such as: What is enough surface crown? What is too much? What causes corrugation? The information is as nontechnical as possible without sacrificing clear guidelines and instructions on how to do the job right.