DEM study on the macro- and micro-responses of granular materials subjected to creep and stress relaxation

The behavior of a typical crushable granular material, i.e., rockfill, during creep and stress relaxation is studied using the discrete element method. Rockfill particles are modeled as breakable agglomerates with time-dependent bond strengths. Parameters are derived from experimental results and reasonable macro-responses are reproduced. The deviator stress level is found to have significant influence on the evolution of the agglomerate breakage number and mechanical coordination number during creep, whereas these two numbers increase slightly during stress relaxation in all situations. The relationship between the macro- and micro-responses is explored. The micro-mechanism of the observed nonisochronous phenomenon is also investigated.