Particle based modeling of shear box tests and stability problems for shallow foundations in sand
The paper deals with the particle based numerical modeling of sand and contains two main items: first, the comparison between lab tests and numerical modeling for shear box tests, and second, the comparison between numerical modeling and ultimate limit state calculations of shallow foundations (DIN 4017). First, the numerical back analysis of shear box tests of dense and loose sand was used to calibrate the material parameters. The paper shows complete load-displacement-curves for the shear box tests and documents that many features, like non-linear stiffness, dilatancy, peak and residual strength values were well reproduced by the PFC-model. Later, these calibrated model parameters were used for stability calculations of shallow foundations under vertical, horizontal and vertical + additional horizontal loading. The numerical model results (failure loads and failure pattern) were compared with classical calculations of the bearing capacity (DIN 4017) and showed a satisfying agreement. The paper documents the up-scaling technique used for the particle size as well as the influence of different scaling factors on the model response and a relation that scales the macroscopic friction angle to the micromechanical contact friction angle for circular particles. Also, the scatter in the model response due to the random packing of the particles is documented.