Drainage systems and the material components comprising those systems are discussed. The effectiveness of existing surface drainage practices are influenced by the types of surface courses which are designed for the pavement and for the shoulder sections. Bituminous concrete specifications in Maryland permit two designated surface mixtures with allowable miximum size of 3/8" materials. Recently, an open graded surface mix designed as a plant mix seal has been applied in the field after test studies. Subsurface drainage practices in Maryland involve three alternative systems: a stabilized subgrade or subbase drainage medium which is extended through the roadway shoulders to the ditch line; a system of continuous longitudinal pipe underdrain; and subgrade drains constructed through the shoulder section. The factors of material availability and the geology and climatic conditions of an area govern which of the three types of drainage will be specified for a proposed project. In the Coastal plain area, extended sand subgrade or sand subbase medium are used; in the clay shale area of the Piedmont Plateau and the mountainous Appalachian Provinces, continuous longitudinal pipe underdrain system or the subgrade drain system may be used. The effect of gradation on permeability is graphically demonstrated, and the use is cited of No. 6 coarse aggregate (essentially ASTM size 57, 1 inch to No. 4) for subgrade drainage in areas of relatively impermeable soils. Strips of this aggregate placed through the shoulders 25 foot intervals were noted to be effective alternates to pipe underdrains.

  • Supplemental Notes:
    • Proceedings from a conference on Utilization of Graded Aggregate Base Materials in Flexible Pavements, March 25-26, 1974, Oak Brook Hyatt House, Oak Brook, Illinois.
  • Corporate Authors:

    National Crushed Stone Association

    1415 Elliot Place, NW
    Washington, DC  United States  20007

    National Sand and Gravel Association

    900 Spring Street
    Silver Spring, MD  United States  20910

    National Slag Association

    300 South Washington Street
    Alexandria, VA  United States  22314
  • Authors:
    • Greene, W B
  • Publication Date: 1974

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00127530
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 7 1976 12:00AM