Influence of the backfill parameters in distinct element modeling (DEM) of a backfill masonry arch bridge through the pfc2d software

Abstract

This paper presents an investigation on how to model a backfill masonry arch bridge using the discrete element method (DEM). The calculations that geotechnical engineers use the most today are elastic calculations, which use an elastic modulus “E”, or plastic analysis that check the equilibrium limit, through a cohesion “c” and a friction angle “”. There is an important problem here in determining these parameters. Soils are not homogeneous materials, but have a great variability. The micromechanics of particles arises here to solve these difficulties PFC2D software is used for this purpose. A certain backfill masonry arch bridge is modelled, with different types of fill, mortar and voussoir materials. Contact bonds and parallel bonds are installed to create the arch at a first stage, positioning balls by their center and radius. Secondly the fill is introduced in several layers and finally the arch is loaded until its collapse in three different load cases. A biaxial test has been programmed using ‘FISH’ code to obtain the micro-parameters used in the model so that they match the macro-parameters obtained from a real biaxial test. Also, a macro within a spreadsheet has been created to simplify the process of introducing the geometry of the arch. Further discussion on the influence of the DEM backfill parameters is presented as well as a sensitivity analysis for the arch bridge, specially with backfill parameters and load position. Advantages, disadvantages and limitations of this method of analysis are identified in relation to other frequently used methods.