Frictional Strain Hardening-softening in Experimental and Numerical Investigationof Arching Effect

In the current paper, the results of a numerical simulation that were verified by a well instrumentedexperimental procedure for studying the arching effect over a trapdoor in sand is presented. Tosimulate this phenomenon with continuum mechanics, the experimental procedure is modeled inABAQUS code using stress dependent hardening in elastic state and plastic strain dependent frictionalhardening-softening with Mohr Coulomb failure criterion applying user sub-routine. The apparatuscomprises of concentric circular trapdoors with different diameters that can yield downward whilestresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole soilmass deforms elastically. However, after an immediate specified displacement, depending on thediameter of the trapdoor, the soil mass behaves plastically. This behavior of sand occurs due to theflow phenomenon and continues until the stress on trapdoor is minimized. Then the failure processdevelops in sand and the measured stress on the trapdoor shows an ascending trend. This indicatesgradual separation of the yielding mass from the whole soil body. Finally, the flow process leads toestablish a stable vault of sand called arching mechanism or progressive collapse of the soil body.