A COMPARATIVE STUDY OF DETERMINATION OF E VALUES IN THE LABORATORY AND IN THE FIELD FOR PAVEMENT LAYER MATERIALS

Abstract

In order to utilize mechanistically based method of pavement design and evaluation there is a need to know the modulii of elasticity of each layer/material in the pavement system. For pavement design and evaluation it is preferable to know the insitu moduli, rather than approximate laboratory moduli. Techniques for measuring insitu moduli is primarily based on surface vibratory technique. Methods for calculations of stresses strains and deflections of pavements based on layered elastic theory have been widely understood and utilized for many years. Ordinarily, elastic moduli have been determined by laboratory testing as a part of the material characterization process. It would be far more useful to establish a correlation between insitu and laboratory moduli of the pavement layer/materials. In the present study insitu modulus of each layer were measured by vibratory testing method on different sections of Village Roads, Major District Roads, State Highways and National Highways. The pavement component materials were extracted from the same locations of the test sections. The respective subgrade soils, WBM materials and surface course materials were brought to the laboratory for experimental testing and analysis. Different type of the specimen were made of these materials and laboratory tests were conducted under controlled condition simulating the stress developed in the pavement layer under actual traffic loads. Samples of subgrade soil iv and the aggregate base course materials were tested in static triaxial loading. The Bituminous Macadam samples were tested in repeated loading in the laboratory to determine resilient (dynamic) characteristics. The CBR soil samples were prepared at Field Moisture Content and Optimum Moisture Content of the subgrade soil collected from the field and correlations were established with field moduli values. Similarly, with WBM samples, triaxial tests were performed at different confining pressure of 0.70, 1.40, 2.10 kg/cm2 and a relationship were established with Edynamic with Estatic • The Bituminous Macadam sample were tested for unconfined static and dynamic triaxial tests. The parameters such as elastic modulus, resilient modulus and Marshall stability were studied. Finally, from laboratory tests and analysis, it has been tried to correlate the insitu moduli with laboratory moduli of the pavement component materials. The results were compared and discussed with other investigators along with recommendations. It is expected tht the findings of the above study would be useful for the development of a suitable approach for the design and evaluation of the flexible pavements based on more realistic strength characterisation tests