INVESTIGATION ON ESTIMATING SOME STRENGTH PARAMETERS OF FLEXIBLE PAVEMENT USING RADIOMETRIC DATA

Abstract

Radiometer is a non imaging sensor, capable of providing multidimensional data. Pavement characteristics are reflected in radiometric data. Therefore radiometer can be utilised to extract the pavement characteristics. Strength of flexible pavement depends upon many factors such as climatic factors, design wheel load, subgrade soil, pavement component materials, environmental factors, thickness of different layers, elastic modulii of different layers, gradation of aggregates used in different layers etc. Gradation or grain size distribution is one of the key property of aggregate. The flexible pavement layers transmit the vertical compressive stresses to the lower layers by grain to grain transfer through the points of contact in granular structure. A granular material designed for maximum stability should posses high internal friction to resist deformation under load. A well graded granular structure consisting of strong graded aggregates can transfer the compressive stresses through a wider area and thus forms a good flexible pavement layer. The load spreading ability of this layer therefore depends very much upon type and gradation of material. Gradation has enormous influence on desirable properties of a pavement layer such as stability, density, drainage, permeability etc. It is to be decided whether to increase the drainage sacrificing the stability or to use densest gradation possible for maximum stability at the risk of poor drainage and increased frost susceptibility in the pavement system. Soil subgrade strength is evaluated, generally through CBR test. It is most widely used test. It is very important parameter in deciding the thickness requirement of pavements. A subgrade with lower CBR value require thicker pavement and vice-versa. In the present study, an attempt has been made to develop the model for finding out gradation, density, moisture content and CBR from the spectral responses obtained by Radiometer.