THE IMPORTANCE OF DRAINAGE IN PAVEMENTS - THE ROLE OF GEOTEXTILES. REINFORCED SOIL AND GEOTEXTILES, PROCEEDINGS OF THE GEOTEXTILES CONFERENCE HELD AT THE INDIAN INSTITUTE OF TECHNOLOGY, BOMBAY, INDIA, DECEMBER 8-9, 1988

The rapid increase in traffic volume through the last decades has accelerated the degradation of pavements. There is overwhelming evidence that a large percentage of the distressed road sections are poorly drained. The presence of water in both flexible and rigid pavement structures can cause large changes in the properties of construction materials and in the pavements response to loads. Most road building agencies provide drainage systems to prevent ground water from reaching the pavement section. The amount of surface water that can enter the road structure from above has often been underestimated. Drainage is essential to increase the service life of many rigid and flexible pavements in roadways, airfields, parking lots, and other paved surfaces that are infiltrated by surface or ground water, specifically those subjected to repeated heavy loads. Such pavements should be designed to minimize the entry of surface water, and they should be provided with adequate drains for removing the water as fast as it enters. The drains are needed for the full width of pavement sections that contain excess water and are subjected to many heavy wheel impacts. Drains may not be required if the combined lateral drainage transmissivity of the base course and the vertical drainage capability of all subgrade materials exceed the water infiltration rate. Drains must remain unclogged and highly permeable for the operational life of the pavement. They must be protected by filters during construction and after the road is completed. A spunbonded polypropylene geotextile like Typar is widely used as an important element in pavement construction. It offers advantages in installation and provides significant savings in construction cost. Its use in drains negates the need for expensive well-graded aggregate. It greatly extends the operational life and significantly reduces maintenance costs. When used in full width drains it also effectively separates aggregate from subsoil and provides structural support due to its high deformation resistance thereby reducing the quantity of aggregate required. For the covering abstract of the conference see IRRD 836241. (Author/TRRL)