This study tested the effectiveness of using dynamic yield strength (DYS) and shear-cell experiments to calibrate the following discrete-element-method (DEM) parameters: surface energy, and the coefficients of sliding and rolling friction. These experiments were carried out on cohesive granules, and DEM models were developed for these experiment setups using the JKR cohesion contact model. Parameter-sensitivity analysis on the DYS model showed that the DYS results in the simulations were highly sensitive to surface energy and were also impacted by the values of the two friction coefficients. These results indicated that the DYS model could be used to calibrate the surface energy parameter once the friction coefficients were fixed. Shear-cell sensitivity analysis study found that the influence of surface energy on the critical-state shear value cannot be neglected. It was inferred that the shear-cell model has to be used together with the DYS model to identify the right set of friction parameters. Next, surface energy was calibrated using DYS simulations for a chosen set of friction parameters. Calibrations were successfully conducted for simulations involving experimentally sized particles, scaled-up particles, a different shear modulus, and a different set of friction parameters. In all these cases, the simulation DYS results were found to be linearly correlated with surface energy and were within 5% of the experimental DYS result. Shear-cell simulations were then used to compare calibrated surface-energy values for the scaled-up particles with the experimentally sized particles. Both the simulations resulted in similar critical-state shear values. Finally, it was demonstrated that a combination of DYS and shear-cell simulations could be used to compare two sets of friction parameters and their corresponding calibrated surface energy values to identify the set of parameters that better represent the flow behavior demonstrated by the experimental system.

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There are great economic incentives motivating the reuse of existing foundations when deteriorated and damaged superstructures are replaced. The increasing reuse of existing bridge foundations warrants investigation into verifying foundation performance and condition of in service bridge foundations. A method is proposed which characterizes the load-response behavior of existing bridge foundations during daily vehicular loading without impeding traffic. It uses a limited number of substructure response measurements from an in service bridge taken during daily traffic heavy truck loadings. The results from this method can be used to verify the vertical, horizontal and rotational load-deformation behavior during daily loadings. Potential applications for the results obtained through this approach are: the detection of structural damage, identification of scour, identification of unknown foundations, and validation the load-deformation behavior predicted by finite element analysis. While loading during the tests would be limited to the magnitude which is caused by daily truck passage, the behavior observed from this loading can be used to update the parameters governing soil behavior which will lead to an improved assessment of the foundation behavior during failure loading or extreme events. A preliminary study is presented as a feasibly study for future use of the proposed method for bridge foundation stiffness identification using substructure measurements.

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