PERMEABLE MATERIALS FOR HIGHWAY DRAINAGE

ALTHOUGH MOST HIGHWAY DEPARTMENTS DESIGN FOR SATURATED ROADBED CONDITIONS, REMOVAL OF EXCESS WATER TO PREVENT PROLONGED FLOODING IS NECESSARY IF MAXIMUM PERFORMANCE IS TO BE OBTAINED. RECOGNIZING THE NEED FOR ADEQUATE INTERNAL DRAINAGE OF HIGHWAYS THE CALIFORNIA DIVISION OF HIGHWAYS HAS BEEN EXPERIMENTING WITH VARIOUS GRADINGS IN AN EFFORT TO UTILIZE BLENDS OF READILY AVAILABLE CONCRETE AGGREGATES IN DRAINAGE SYSTEMS. THE PAPER REVIEWS PAST SPECIFICATIONS FOR PERMEABLE MATERIALS AND GIVES THE RESULTS OF AN EXTENSIVE SERIES OF LABORATORY PERMEABILITY TESTS USED IN DEVELOPING GRADING LIMITS FOR A NEW CLASS OF PERMEABLE MATERIAL. GRADATION CURVES AND PERMEABILITIES ARE GIVEN FOR TYPICAL COMBINATIONS TESTED. BASIC DATA FOR ALL OF THE TESTS ARE SUMMARIZED IN TABLES. THE PAPER INCLUDES A BRIEF DISCUSSION OF A METHOD FOR ESTIMATING THE WATER-REMOVING CAPABILITIES OF BLANKETS OF PERMEABLE AGGREGATES, AND GIVES A CHART EVALUATING TYPICAL LAYERS. ALTERNATIVE DESIGNS UTILIZING TWO -LAYER SYSTEMS ARE NOTED AS A MEANS FOR DRAINING HIGHWAY PAVEMENTS WHEN LARGE QUANTITIES OF WATER ARE ANTICIPATED. /AUTHOR/