Drainability Of Granular Bases For Highway Pavements

This report presents a new method for analysis of the drainage of a saturated base. Starting from basic principles of water retention and flow in porous media, this analysis leads to some new methods for the estimation of minimum degrees of saturation, drainable porosities and drainage times. This study found that current practices in the FHWA subdrainage design manual tend to overestimate the amount of drainage from fine-grained bases and greatly underestimate the amount of drainage from coarse-grained bases. Also of importance is the ability to estimate the lowest degree of saturation that can be achieved through gravity drainage. The new methods for the analysis of pavement subdrainage are implemented in two computer programs: (1) SUBDRAIN - simulates the drainage of water from a pavement base that is initially saturated and provides estimates of the minimum degree of saturation in the field and key drainage times; and (2) SUBDRAIN-C - simulates the flow of water into and out of the base over a period of years - the inputs include a long-term record of 15-minute rainfall data and the output shows how often the base is likely to be saturated or nearly saturated.

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.

Only book world-wide addressing this topic. The principal output of the European co-operative Action on "Water Movements in Road Pavements & Embankments". Provides unique guidance on assessing water condition and its affects on road performance. Provides unique guidance on assessing and ameliorating contaminant movement in pavement groundwater. Written by leading experts in Europe.

Paper 1: This study covers a condition survey in Indiana of 328.5 mi. of rigid pavements constructed with granular bases. Paper 2: All new concrete pavement in Illinois has been placed on granular subbase where the natural soil is fine-grained and heavy truck traffic is expected. The lower cost of constructing the trenched undrained subbase was a deciding factor in the preference shown for this type of subbase.