TRANSMISSIVITY AND STORAGE CHARACTERISTICS OF SOILS

Abstract

One of the main objects of current highway research is the development of improved design methods for flexible pavements. Till now the empirical methods have been at wider use because of their simplicity. These methods, however, are ad-hoc in nature. This led to the invention of structural design approach considering flexible pavement as layered system. The three-layer elastic system is considered to be a reasonable approximation of a flexible pavement structure. The validity of tabulated solutions given by Jone are beyond any doubt and these can be applied to any situation. But Jone solution can be satisfactorily used to solve problem provided the values of variables fit in to the tabulated values. The graphs given by Peattie are also unsuccessful in avoiding the problems of interpolation or extrapolation calculations. Moreover, a lot of time and care is needed in arriving at the solution even using the available graphs produced by Peattie. Therefore, there is a need to bridge these shortcomings and to achieve an accurate structural design approach based upon sound theory. The availability of high-speed digital computers has helped in development of pavement design theories during recent years. Many softwares are available in international market but none of them can be called as purely theoretical as they use—certain—emper-ical- equations_ derived _for certain soil conditions. Thus _ their_ application to different situations is doubtful. A software FLEPANJ is developed in this study to arrive at accurate structural design approach based upon Jones tabulated solutions for three layer flexible pavement system. It gives stresses and strains at each critical interface by using Jones solutions. Thus, it avoids the problem of interpolation or extrapolation calculations. FLEPANJ exploits the Jones tabulated values to obtain the deflection of each layer, interface deflections and deflection at the subgrade level. It predicts the number of load repetition leading to failure based upon most widely accepted AASHO model. It also evaluates the pavement based upon Present Serviceability Index (PSI) criteria by predicting the residual number of repetitions, a flexible pavement can further take in terms of both, given axle load and standard axle load. Finaly, FLEPANJ gives .complete picture of pavement in graphical form for all the calculated variables. It gives the flexibility to the user to use any system of units provided it is consistent throughout. Thus, FLEPANJ is a powerful tool in the hands of the pavement engineer as it aims to achieve at an accurate structural design approach based upon three-layer elastic theory. (