SLOPE VARIANCE AS A MEASURE OF ROUGHNESS AND THE CHLOE PROFILOMETER

Abstract

A SHORT DISCUSSION OF EXISTING PAVEMENT ROUGHNESS MEASURING DEVICES IS GIVEN. THE RATIONALE IS DESCRIBED BY WHICH THE STATISTIC, SLOPE VARIANCE, WAS CHOSEN AS A MEASURE OF PAVEMENT ROUGHNESS AT THE AASHO ROAD TEST FOR USE AS AN ELEMENT OF SERVICEABILITY. THE CHOICE OF THE SLOPE RATHER THAN THE DISPLACEMENT OR ELEVATION PROFILE IS DISCUSSED. THE CHLOE PROFILOMETER, A DEVICE DEVELOPED AT THE ROAD TEST FOR DETERMINATION OF THE SLOPE VARIANCE ON PAVEMENTS UN THE FIELD, IS DESCRIBED. THE CHLOE PROFILOMETER IS A RELATIVELY SIMPLE, ELECTRONIC-MECHANICAL DEVICE. IT IS TOWED BY A VEHICLE OVER ANY SECTION OF PAVEMENT. THREE STATISTICS, THE NUMBER OF SAMPLE POINTS (SLOPE IS SAMPLE AT 6-IN. INTERVALS ALONG THE PAVEMENT WHEELPATH), THE SUM OF THE DEVIATIONS OF THE SLOPES FROM AN ARBITRARY REFERENCE VALUE, AND THE SUM OF THE SQUARED DEVIATIONS OF THE SLOPES FROM THE SAME REFERENCE ARE DETECTED, COMPUTED AND DISPLAYED ON THE PANEL OF THE ELECTRONIC DEVICE THAT IS IN THE TOWING VEHICLE. THESE THREE STATISTICS CAN BE COMBINED TO DETERMINE THE SUMMARY STATISTICS, SLOPE VARIANCE. THE DEVICE USES SOLIDSTATE CIRCUITRY (TRANSISTORS AND DIODES). IT IS EXTREMELY COMPACT AND RUGGED. IT IS EASY TO OPERATE REQUIRING NO ELECTRONIC TECHNICIANS. IT USES PLUG-UN PRINTED CIRCUIT BOARDS TO PERMIT RAPID FIELD MAINTENANCE BY NON-TECHNICAL PERSONNEL. PROVISION IS INCLUDED FOR FIELD CALIBRATION AND TESTING OF ALL COMPONENTS TO INSURE THAT EVERYTHING IS WORKING PROPERLY. THE COST FOR LABOR AND MATERIALS FOR CONSTRUCTING ONE UNIT IS APPROXIMATELY $6,000 EXCLUDING OVERHEAD AND PROFIT. A DISADVANTAGE OF THE UNIT IS THAT IN ITS PRESENT FORM IT CANNOT BE OPERATED WHILE RECORDING AT A SPEED IN EXCESS OF 5 MPH. HOWEVER, PAVEMENTS UNDER STUDY ARE GENERALLY SAMPLED IN SHORT SEGMENTS. BETWEEN SUCH SAMPLE SEGMENTS THE DEVICE CAN BE TOWED AT NORMAN ROAD SPEEDS. /AUTHOR/